Feeding Values of Indigenous Browse Species and Forage Legumes for the Feeding of Ruminants in Ethiopia: A Meta-Analysis

Abstract

The foliage of browse species and forage legumes has good nutritional value and can be utilized as a protein source in ruminant diets. However, its efficient utilization requires the establishment of a comprehensive database of feeding values. Two databases, i.e., forage nutritive value (92 studies) and in vivo animal performance (62 feeding experiments), were built to assess the feeding value of the foliage of browse species and cultivated forage legumes in Ethiopia. The forage nutritive value data (chemical composition and in vitro digestibility) were summarized as descriptive statistics. The analysis of in vivo data was conducted using a mixed model procedure with fixed (forage supplement) and random (studies) factors. Forage categories had crude protein (CP) ranging from 17.6 ± 5.2% (indigenous browse species) to 22.4 ± 4.5% (multipurpose fodder tree/shrub species), respectively. Variations were observed in CP values between the vegetative and blooming stage harvesting of herbaceous forages (22.7 ± 4.1% versus 19.8 ± 3.5%). The leaves contained more CP than the twigs in multipurpose fodder tree/shrubs (22.8 ± 3.2% versus 18.8 ± 0.6%) and the pods in indigenous browse species (18.0 ± 5.0% versus 15.3 ± 2.3%). However, the greatest mean in vitro organic matter digestibility (IVOMD) of 70.1 ± 10.8% was observed in the foliage of indigenous browse species. The variation in IVOMD was small among the forage categories (61.2 ± 11.2%–63.5 ± 10.8%). Twigs of the multipurpose fodder tree/shrub species had the lowest IVOMD of 53.0 ± 6.9%. Herbaceous forage legumes tended to have higher NDF and ADF values than the other forage categories. In terms of nutrient concentration and digestibility, large variations were observed within the same forage categories and species. The supplementation of forage, on average at 277.5 ± 101.4 g/day (±SD), to a low-quality basal diet resulted in a significant (p < 0.05) improvement in the apparent digestibility of DM, CP, and NDF as well as the daily intake of DM, CP, and metabolizable energy (ME). The application of sole forage supplementation was determined to have comparable effects on DM intake (p = 0.2347) with dietary supplements based on concentrate feedstuffs. However, CP intake (p = 0.0733) tended to be lower for forage over the concentrate treatment. The averaged daily gain (ADG) of the animals was significantly increased (p < 0.05) by 71.2% due to the forage supplement compared to unsupplemented treatment (11.6 ± 5.47 g/d (±SE) vs. 40.3 ± 4.99 g/d (±SE)). Overall, the nutrient utilization and production performance of animals fed with low-quality basal diets could be improved when an appropriate amount of forage is included as supplement. The large variation recorded in the nutritional composition of browse species and forage legumes could provide an opportunity to screen for species and varieties with superior nutritional quality.

1. Introduction

Livestock production is the backbone of Ethiopia’s agricultural sector, and it supports the livelihood of millions of rural smallholders and urban dwellers. Livestock delivers many services, including improved food and nutrition security, increased recycling of organic matter and nutrients, and associated soil fertility amendments, adding value to crop residues by turning them into nutrient-rich foods, income generation, and animal traction [1]. Ethiopia is a country known for its large livestock population of diverse species and breeds. According to the current national data [2], the livestock population of the country is dominated by ruminant species such as cattle, goats, and sheep. This indicates that livestock production mainly based on ruminant species rearing plays a vital role in the food security and economic development of the nation. Despite the documented valuable contribution of livestock to food security and the available potential for ruminant production, current overall productivity and production performance are minimal. It has been reported that feed and feeding-related problems are among the top-mentioned constraints of livestock production, particularly in low- and middle-income countries like Ethiopia [3]. Similarly, many recently published studies [4,5] have revealed the prevailing problem of feed shortage in the different production systems of Ethiopia. The national feed balance analysis revealed a feed deficiency of 9% in total DM availability and 45% and 42% in ME and CP, respectively, in Ethiopia [6]. Thus, the country’s livestock production is seriously hindered by the scarcity of good-quality feed. Overall, the reported gaps in the supply of quality feed [4,6] and growing livestock populations [7] necessitate more efforts and investments in good-quality fodder production.

In Ethiopia, the total basal diets used for the feeding of ruminants are obtained from different sources, including natural pastures, crop residues, aftermath grazing, and some unconventional sources [8,9]. Natural pastures and crop residues are major sources that contribute about 94.2% of the total national feed supply [7]. In contrast, the same report mentioned an insignificant contribution of concentrate feedstuffs and improved cultivated forages. On the other hand, a part of the large share in feed supply, natural pasture, and crop residues is characterized by low nutritive value and fluctuations in availability and quality. The natural pasture and crop residues produced in Ethiopia have poor digestibility and low metabolizable energy (ME) values because of the high concentration of structural carbohydrate or fiber (NDF: 595–792 g/kg and 671–770 g/kg DM, respectively) and low protein content (CP: 32–72 g/kg and 63–92 g/kg DM, respectively) [10]. In general, if adequate amounts of good-quality fodder are not produced year-round and animals are reared entirely on low-quality diets, it will result in lower overall productivity and increase the risk of environmental degradation [11].

The efficient utilization of the available feed resources, such as crop residues and natural pastures, could be a potential option to fill the current feed supply gap in Ethiopia [7]. It has been suggested that the feeding value of these low-quality roughages needs to be upgraded through appropriate supplementation strategies that target the most limited nutrients [10,12]. However, concentrate feedstuffs, including agro-industrial byproducts, have good nutritional value, which make them ideal sources of supplements [13]. Their utilization is limited to urban and peri-urban livestock production [9,13], and they are barely utilized by smallholder farmers because of the high cost and unreliable supply [3]. Many research efforts have been made towards the search for affordable options from locally available resources to substitute the concentrate feedstuffs. It has been suggested that the utilization of the foliage (leaves and pods) of indigenous browse species [14], cultivated herbaceous forage legumes [15], and multipurpose fodder trees/shrub species [16,17,18] is a potential alternative for smallholder livestock keepers. The foliage of browse species and cultivated forage legumes have good nutritive value; they are particularly rich in CP and have better digestibility compared to natural pasture hay and crop residues [10]. This nutritional fact may make the utilization of the foliage of browse species and cultivated forage legumes as a protein source in ruminant diets sound. The proper integration of cultivated forage legumes into the feed niches in general is advisable to supply good-quality fodder year-round [11,19].

On the other hand, although an increasing body of evidence on the nutritional characteristics and animal responses to the diets containing foliage of browse species and forage legumes has been generated, a definitive recommendation has yet to be established regarding their inclusion in ruminant diets for better nutrient utilization and production performance. The reported large variation in the nutritional value data among studies and the discrepancies often reported on the inclusion levels and animal’s production responses to the diets contain foliage of these forage groups are the major limitations remaining. The nutritive values of forage materials can be influenced by multiple factors, such as forage species and variety, growing season and environment, plant parts analyzed, and postharvest management practices. These sources of variations together with the nutritional characteristics of the basal diets and animal experiment settings can be cumulatively attributed to the inconsistent effects of browse species and forage legumes supplementation on the nutrient utilization and production performance of ruminants. Overall, comprehensive information on the feeding value of fodders obtained from browse species and cultivated forage legumes is required to draw a generous recommendation on the efficient utilization of foliage as a source of protein supplement in low-quality natural pasture and crop-residue-based ruminant diets to achieve a significant improvement in livestock productivity. Therefore, it is very important to compile data from different literature sources to generate a more comprehensive and predictive database regarding the nutritive value and animal production responses to diets containing these fodder sources. Meta-analysis is an important statistical tool that enables the systematic collection and analysis of information from a wide range of studies, which are characterized by substantial heterogeneity in aspects, such as diets, animal factors, experimental designs, measurement methods, etc. [20]. The objectives of this study were first to summarize the nutritive value of indigenous browse and forage legume species grown in Ethiopia and, then, to assess the effects of these fodder sources on nutrient utilization and production performance of ruminants when included in low low-quality basal diets as a supplement. Thus, the meta-analysis approach was followed to systematically collect, analyze, and interpret available literature data to generate valuable insights into the potential feeding value of browse species and forage legumes in Ethiopia.

2. Materials and Methods

2.1. Database Development

Two independent datasets on the nutritional value of forage (chemical composition and in vitro digestibility) and in vivo animal responses were built using peer-reviewed journal articles. Literature search of journal articles was completed between November 2021 and January 2022 for forage nutritional value studies, and between October 2022 and January 2023 for in vivo animal experiments. Herzing’s Publish or Perish free package was used to retrieve valid studies on this topic from Ethiopia. The search was made on common Web databases such as Google Scholar, Scopus, and PubMed. The search was completed without the establishment of a structured protocol, and, thus, it was not registered in any publisher database. For the in vitro nutritional value studies, terms including “Browse species”, AND “Forage Legumes” together with “Nutritive value”, “Chemical composition”, and “Digestibility”, with country name ‘Ethiopia’ were applied for literature search. Meanwhile, “Forage feeding” with “sheep”, “goats”, “cattle”, “ruminants, AND “Ethiopia” were used for literature search of in vivo animal experiments.

Articles were included in the in vitro database if the nutritive measurements were related to the specified forage species (such as forage legumes and browse species), studied in Ethiopia and published in English. The papers should have also reported nutritive value metrics information of chemical composition (DM, ash, CP, NDF, ADF, ADL) in %DM or g/kg DM, in vitro OM digestibility in %, and ME in MJ/kg DM. When the paper reported only IVOMD value, the ME content was estimated using equation of Saha et al. [21]: ME MJ/kg DM = 0.15 × IVOMD−0.6. In addition, if the papers reported plant phenolic content, particularly condensed tannin concentration, it was recorded in the database. To facilitate a more efficient search process and help in the determination of study inclusion or exclusion, nutritional value data were further categorized into sub-datasets on chemical composition, in vitro digestibility, and metabolizable energy value. Finally, a total of 93 papers reporting the nutritional values were integrated into the databases dealing with the nutritive value of the forages.

A second database on in vivo animal experiments was constructed using 269 dietary treatments collected from 62 selected animal experiments in Ethiopia. Papers that met the following criteria were included in the database: (1) studies that used either sheep or goats as animal experiment under controlled experimental design; (2) studies that compared two or more dietary treatments (control treatment: without supplementation; and experimental treatments: supplemented with foliage of browse species and forage legumes, concentrate feeds, or concentrate feeds partially substituted by foliage); (3) studies that reported nutritional composition of basal diets, experimental foliage, and feed ingredients; and (4) studies that recorded and reported mean data of animal performance parameters (diet apparent digestibility, feed intake measurements, weight gain, and carcass yield). Moreover, information on animal feeding patterns, such as the daily supplementation level on DM bases and the substitution rate of concentrate feed by the forages, was also important criteria in the paper selection. At the end, treatment means for the variables, such as initial body weight of animals (BW), dry matter intake (DMI), crude protein intake (CPI), neutral detergent fiber intake (NDFI), metabolizable energy intake (MEI), feed conversion efficiency (FCE = ADG/DMI), average daily weight gain (ADG), carcass dressing percentage (empty body weight based), and apparent digestibility of DM and nutrients (CP and NDF), were collected.

2.2. Statistical Analysis

2.2.1. Nutritional Value Data

The retrieved studies showed a wide range of heterogeneity regarding the studied plant species and varieties, agroecological conditions, sampling seasons, and the plant morphological components analyzed. If these multiple factors were simultaneously considered, it might have led to extraction of data from only few studies, which could increase the potential for publication bias [22]. Therefore, to address this limitation, the plant species were categorized into three groups using some common criteria (such as growth patterns and modes of production). The three major groups of the analyzed plant species were herbaceous forage legumes, multipurpose fodder tree/shrub species, and indigenous browse species. Forages grouped under herbaceous forage legumes are classes of improved forage species that are selected or developed and promoted through the research system of the country for animal feeding purposes. Multipurpose fodder trees/shrubs are leguminous plants grown by farmers for multiple uses, such as animal feed and human food (e.g., Cajanus cajan), soil fertility improvement, environmental protection (soil and water conservation), fencing, and fuel wood sources. Indigenous browse species include any trees and shrubs grown in the natural environment without human intervention but that can provide feed for animals. In addition, some common species were picked from each category and analyzed.

Prior to the actual analysis, statistical outlier data were identified in boxplots using Tukey’s procedure [23]. In the procedure, Q₁ represents the first quartile and Q₃ represents the third quartile, and data falling below “Q₁−1.5×(Q₃−Q₁)” or exceeding “Q₃ + 1.5 × (Q₃−Q₁)” were identified as outliers and removed from the database. Chemical composition, in vitro digestibility, metabolizable energy, and tannin concentration data were summarized in descriptive statistics (mean, standard deviation, minimum, and maximum) of SPSS package (SPSS, Version 27).

2.2.2. Animal Experiment Data

The number of observations used for the analyses varied between the independent and the response variables. For the whole in vivo animal response data, summary statistics such as mean, standard deviation, minimum and maximum values were computed. The database was divided into two subsets, the first to compare dietary treatments comprising forage supplementation against a control dietary treatment with no supplements (negative control), and the second subset comparing forage supplementation with sole concentrate supplements and concentrate supplement partially substituted with different levels of forage supplements. Weighing of treatment means was carried out using number of observations (replications) per dietary treatment, as partly applied in some previous similar studies [24,25]. The inverse of the number of replicates was used for weighing the treatment means. But, to maintain the expression of dispersion in the original measurement scale during meta-analysis [26], common weighing factor was computed by dividing each weight by mean value of all weights. Then, statistical outlier data were systematically removed from both datasets independently using the Tukey procedure [23].

Two separate meta-analyses were performed using a mixed procedure of SAS software (Version 9.4, SAS Institute). The mixed model combined two factors: dietary treatment as a fixed factor and studies by dietary treatment interaction (only if significant at p < 0.05) as random factors. Initial body weight of the animals was included as a covariate in the model for the analysis of nutrient intake variables. The residual mean square error (RMSE) and Akaike’s information criterion (AIC) were used for the model fit evaluation and reported in the Results section. Significant differences were set at p < 0.05. Means were compared using the least significant difference test with the P-DIFF option of the LSMEANS statement in SAS code. For the ease of statistical analysis, all variables were kept in separate datasets, and the weighing statement of SAS was included to weigh each datum.

The model used was Y = μ + T_i + S_j + e_ij, where μ = overall means, T_i = fixed effect of dietary treatments, S_j = random effect of the studies, and e_ij is the residual errors.

When the analysis showed significant interaction effects between dietary treatments and studies, it was included as a random factor and the model was modified as follows:

Y = μ + T_i + S_j + TS_ij + e_ij, where μ = overall means, T_i = fixed effect of dietary treatments, S_j = random effect of the studies, TS_ij = interaction effect between dietary treatment and study, and e_ij is the residual errors.

3. Results

3.1. Description of Browse Species and Forage Legumes Included in Chemical Composition and in Vitro Digestibility Database

In Ethiopia, many browse species and cultivated forage legumes have been studied as valuable protein sources for livestock feeding in general. Descriptions of browse species and forage legume species studied in Ethiopia for their feeding value are summarized in

Table 1. Descriptions of forage species included in chemical composition and in vitro digestibility database.

Forage Categories	N (S)	Selected Species from Each Category	R
Herbaceous forage legumes	33 (10)	Medicago sativa	8
		Lablab purpurea	6
		Desmodium intortum (Greenleaf)	5
		Desmodium uncinatum (Silverleaf)	6
		Vicia species	7
Multipurpose fodder tree/shrub species	22 (6)	Cajanus cajan (Pigeon pea)	10
		Tree lucerne (Tagasaste)	7
		Sesbania sesban	11
		Leucaena species	6
Indigenous browse species	53 (148)	Acacia species (17 different types)	19
		Vernonia amygdalina	12
		Balanites aegyptiaca	8
		Cordia africana	7
		Ficus species (Four different types)	7
		Rhus natalensis	7
		Grewia species (Six different types)	7

N: number of studies (number of species), R: number of studies reporting specified species.

. For the current review, the analysis integrated the nutritive value data of 175 forage species documented in 92 studies. Regarding the forage types, indigenous browse species were the predominant group, with 148 species reported in the included studies. Acacia species were identified as the dominant and diverse species among indigenous browse species with about 17 types of acacia species investigated. Grewia and Ficus followed Acacia species in terms of the number of species (six and four species, respectively) being studied in various sources. Furthermore, species, such as Cordia africana, Vernonia amydalina, Ficus thonningii, and Rhus natelensis, were also included in many studies reporting the nutritional values of indigenous browse species.

Regarding forage legumes, about 16 species that were categorized under herbaceous forage legumes and multipurpose fodder tree/shrub species were included in the database of chemical composition and in vitro digestibility (Table 1). Here, more than one species was mentioned under the forage Vetch (Vicia) and Leucaena species for ease of data management and analysis. Many varieties of cultivated forage legumes with different growth patterns (herbaceous, tree, and shrubs) were analyzed. The common multipurpose fodder tree/shrub species grown in different agroecology and production systems of Ethiopia for animal feed use include sesbania (Sesbania sesban), tree lucerne/Tagastate (Chamaecytisus palmensis), Leucaena (Leucaena leucocephala, Leucaena pallida, Leucaena diversifolia), and pigeon pea (Cajanus cajan). Large genetic resources of promising species and varieties of herbaceous forage legumes were studied in Ethiopia. In the current analysis, forage vetch species comprising Vicia atropurpurea, Vicia dasycarpa, Vicia narbonensis, Vicia sativa, and Vicia villosa were very diverse in type and collectively evaluated. Similarly, the nutritional value of Medicago sativa (alfalfa), Lablab purpurea, and Desmodium species was included in the database for the nutritional value analysis.

3.2. Mean Nutritional Values of Main Forage Categories

All data included in the database were analyzed for the main forage categories (herbaceous forage legumes, multipurpose fodder tree/shrub species, and indigenous browse species). The nutritive values of whole herbaceous forage legumes harvested at two maturity stages and the morphological components (leaf, twigs, pods, and whole foliage) of multipurpose fodder trees/shrubs and indigenous browse species are presented in

Table 2. Chemical composition and in vitro organic matter digestibility value of forage categories in Ethiopia.

Parameters		Herbaceous Forage Legumes			Multipurpose Fodder Tree/Shrub Species				Indigenous Browse Species
		Blooming Stage	Vegetative Stage	Overall	* Foliage	Leaves	Twigs	Mean	* Foliage	Leaves	Pods	Overall
DM%	Mean ± SD	90.7 ± 2.3 (n = 84)	91.6 ± 2.0 (n = 9)	90.7 ± 2.3 (n = 93)	90.8 ± 2.7 (n = 23)	92.5 ± 2.0 (n = 33)	-	91.8 ± 2.5 (n = 56)	92.4 ± 2.5 (n = 126)	92.0 ± 2.3 (n = 194)	90.5 ± 1.7 (n = 14)	92.1 ± 2.4 (n = 334)
	Range	81.7–96.2	88.1–95.0	81.7–96.2	84.0–95.8	88.5–95.4	-	84.0–95.8	87.4–98.5	83.2–96.8	87–93.2	83.2–98.5
Ash %DM	Mean ± SD	10.3 ± 2.3 (n = 89)	10.6 ± 2.2 (n = 15)	10.4 ± 2.2 (n = 104)	9.1 ± 1.6 (n = 37)	7.8 ± 2.6 (n = 35)		8.5 ± 2.2 (n = 72)	9.2 ± 2.8 (n = 115)	10.4 ± 3.2 (n = 278)	6.5 ± 3.2 (n = 20)	9.9 ± 3.3 (n = 420
	Range	5.4–14.5	5.8–15.1	5.4–15.1	4.9–13.8	4.3–13.7		4.3–13.8	4.2–16.9	4.1–18.9	2.0–15.5	2.0–18.9
CP (%DM)	Mean ± SD	19.8 ± 3.5 (n = 101)	22.7 ± 4.1 (n = 17)	20.3 ± 3.7 (n = 118)	21.7 ± 3.6 (n = 39)	22.8 ± 3.2 (n = 41)	18.8 ± 0.6 (n = 4)	22.1 ± 3.4 (n = 84)	16.3 ± 3.6 (n = 128)	18.0 ± 5.0 (n = 360)	15.3 ± 2.3 (n = 20)	17.6 ± 4.8 (n = 514)
	Range	11.3–30.1	13.3–29.1	11.3–30.1	14.9–30.6	16.2–30.9	18.1–19.4	14.9–30.9	8.8–25.5	7.8–30.0	10.3–18.5	7.8–30.0
NDF (%DM	Mean ± SD	47.7 ± 9.4 (n = 104)	46.9 ± 10.3 (n = 19)	47.6 ± 9.5 (n = 123)	48.7 ± 10.0 (n = 38)	41.6 ± 14.0 (n = 39)	58.3 ± 7.2 (n = 4)	45.8 ± 12.7 (n = 81)	44.8 ± 10.1 (n = 133)	40.1 ± 12.9 (n = 345)	40.2 ± 8.5 (n = 190	41.4 ± 12.2 (n = 498)
	Range	29.3–72.0	25.8–65.1	25.8–72	23.8–68.6	20.0–66.8	47.9–63.2	20.0–68.6	27.1–68.8	12.8–71.0	18.4–51.5	12.8–710
ADF (%DM)	Mean ± SD	33.6 ± 7.8 (n = 106)	33.1 ± 7.8 (n = 19)	33.5 ± 7.8 (n = 125)	33.9 ± 7.6 (n = 37)	28.0 ± 10.6 (n = 37)	42.4 ± 2.0 (n = 4)	31.6 ± 9.7 (n = 78)	30.4 ± 7.6 (n = 133)	27.6 ± 10.4 (n = 353)	30.4 ± 10.0 (n = 18)	28.6 ± 10.0 (n = 507)
	Range	13.7–55.0	14.7–43.7	13.7–55.0	16.6–45.9	13.1–48.8	40.1–44.6	13.1–48.8	15.2–49.9	8.5–53.3	12.0–46.5	8.5–58.9
ADL (%DM)	Mean ± SD	7.4 ± 2.8 (n = 93)	7.5 ± 2.8 (n = 16)	7.4 ± 2.8 (n = 109)	12.0 ± 5.7 (n = 30)	8.0 ± 3.1 (n = 26)	-	10.1 ± 5.0 (n = 57)	9.5 ± 3.3 (n = 118)	11.4 ± 5.4 (n = 256)	8.1 ± 3.3 (n = 13)	10.9 ± 5.0 (n = 395)
	Range	2.2–15.8	2.0–13.3	2.0–15.8	4.6–20.7	2.7–13.8		2.7–20.7	3.4–18.1	2.3–34.6	3.9–14.4	2.3–34.6
IVOMD (%)	Mean ± SD	63.1 ± 11.2 (n = 29)	65.1 ± 9.3 (n = 6)	63.5 ± 10.8 (n = 35)	58.5 ± 13.1 (n = 17)	66.4 ± 7.1 (n = 15)	53.0 ± 6.9 (n = 4)	61.2 ± 11.2 (n = 36)	70.1 ± 10.8 (n = 20)	60.5 ± 12.3 (n = 145)	59.4 ± 10.8 (n = 4)	61.6 ± 12.4 (n = 170)
	Range	42.2–82.0	50.5–79.5	42.2–82.0	51.6–92.4	51.3–76.0	49.1–63.3	49.1–92.4	51.1–84.8	33.2–95.6	45.7–72.0	33.2–95.6
ME (MJ/kg DM)	Mean ± SD	8.9 ± 1.72 (n = 26)	8.9 ± 0.82 (n = 9)	8.9 ± 1.5 (n = 35)	8.0 ± 1.4 (n = 17)	8.9 ± 1.2 (n = 20)	7.3 ± 1.0 (n = 4)	8.4 ± 1.4 (n = 41)	7.3 ± 1.7 (n = 20)	8.3 ± 1.6 (n = 116)	8.4 ± 1.0 (n = 4)	8.2 ± 1.6 (n = 191)
	Range	5.7–11.3	7.7–10.2	5.7–11.3	7.1–10.6	7.1–10.8	6.8–8.9	6.8–10.8	4.9–11.6	4.1–12.4	7.7–9.9	4.1–12.4

*: foliage represents edible portions (leaf, twigs, fine stem and reproductive parts) of trees, shrubs and forbs together, n: number of records, DM—dry matter, CP—crude protein, NDF—neutral detergent fiber, ADF—acid detergent fiber, ADL—acid detergent lignin, IVOMD—in vitro organic matter digestibility, ME—metabolizable energy.

. The result showed variations in nutrient concentrations and in vitro digestibility among the forage categories as well as the studies included in the database. Pods of indigenous browse had the lowest ash content (6.5 ± 3.2%), while whole herbaceous forage legumes and leaves of indigenous browse species contained comparable ash values, which was the highest. The overall mean value revealed that multipurpose fodder tree/shrub species had a maximum CP content of 22.8 ± 3.2%, followed by herbaceous forage legumes (20.3 ± 3.7%), while indigenous browse species had the minimum CP value (17.6 ± 4.8%). Herbaceous forage legumes harvested at the vegetative stage contained more CP (22.7 ± 4.1%) than forage harvested at the blooming stage (19.8 ± 3.5%). The results also exhibited differences in CP content among the morphological components of the multipurpose fodder tree/shrubs and indigenous browse species. For both forage categories, the leaf portion contained the maximum CP (22.8 ± 3.2% and 18.0 ± 5.0%, respectively), whereas the twigs of multipurpose fodder tree/shrub species (18.8 ± 0.6%) and the pods of indigenous browse species (15.3 ± 2.3%) contained the lowest values of CP. The fiber concentration of the forages was assessed using the reported NDF, ADF, and ADL concentration. From the overall mean value, herbaceous forage legumes contained higher fiber levels (47.6 ± 9.5% NDF and 33.5 ± 7.8% ADF) than indigenous browse species (41.4 ± 12.2% NDF and 28.6 ± 10.0% ADF). The values of NDF and ADF were intermediate for multipurpose fodder tree/shrub species (45.8 ± 12.7% NDF and 31.6 ± 9.7%, respectively). Herbaceous forage legumes contained the minimum mean ADL (8.0 ± 3.1%) compared to the other forage categories. The variation in the content of fiber fractions between the harvesting stages of whole herbaceous forage legumes was minimal. In contrast, large variations were recorded among morphological fractions of multipurpose fodder tree/shrub species in fiber contents, with the twigs containing more NDF and ADF (Table 2).

As reported in Table 2, regardless of the harvesting stage of herbaceous forage legumes and morphological fractions of multipurpose fodder tree/shrub species and indigenous browse species, organic matter digestibility was comparable among the forage categories, with IVOMD values ranging from 61.2 ± 2.11% to 63.5 ± 10.8%. The greatest IVOMD values were recorded from herbaceous forage legumes harvested at the vegetative stage with 65.1 ± 9.3%, leaves of multipurpose fodder tree/shrub species with 66.4 ± 7.1%, and foliage of indigenous browse species with 70.1 ± 10.8%. The result also showed comparable mean ME contents among the forage categories, with a value of 8.1 ± 1.4 to 8.9 ± 1.5 MJ/kg DM (Table 2). The twigs portion of multipurpose fodder tree/shrub species and whole foliage of indigenous browse tended to have a lower ME concentration among the studied morphologic fractions. Overall, despite outlier data exclusion from analysis at different levels, substantial variation in nutritive value was observed within the same forage categories, harvesting stages, and morphological fractions analyzed. These variabilities are evident from the results of standard deviation and range values (minimum–maximum) reported in Table 2.

3.3. Nutritive Value of Selected Species from Herbaceous Forage Legumes

The nutrient concentrations and in vitro organic matter digestibility of the selected herbaceous forage legumes analyzed in the form of fresh harvest and hay are presented in

Table 3. Chemical composition and in vitro organic matter digestibility of selected herbaceous forage legumes in Ethiopia.

Parameters		Medicago sativa			Vicia Species			Lablab purpurea			Desmodium intortum			Desmodium uncinatum
		Fresh	Hay	Overall	Fresh	Hay	Overall	Fresh	Hay	Overall	Fresh	Hay	Overall	Fresh	Hay	Overall
DM%	Mean ± SD	90.6 ± 1.0 (n = 32)	91.8 ± 4.4 (n = 3)	90.7 ± 1.5 (n = 35)	89.9 ± 1.4 (n = 15)	88.8 ± 2.3 (n = 11)	89.4 ± 1.9 (n = 26)	92.7 ± 1.1 (n = 12)	91.3 ± 2.6 (n = 9)	92.1 ± 1.9 (n = 21)	-	-	92.3 ± 2.9 (n = 3)	92.7 ± 1.5 (n = 5)	88.7 ± 6.4 (n = 3)	91.2 ± 4.2 (n = 8)
	Range	88.2–92.1	87.5–96.2	87.5–96.2	88.1–92.1	85.0–92.7	85.0–92.7	91.1–94.7	87.2–95.8	87.2–95.8	-	-	89.2–95	90.7–94.2	81.7–94.4	81.7–94.4
Ash %DM	Mean ± SD	11.7 ± 1.7 (n = 46)	12.9 ± 0.3 (n = 2)	11.8 ± 1.6 (n = 48)	9.1 ± 1.2 (n = 16)	10.2 ± 1.7 (n = 6)	9.4 ± 1.4 (n = 22)	6.4 ± 1.4 (n = 12)	10.0 ± 1.4 (n = 9)	8.0 ± 2.3 (n = 21)	8.6 ± 2.3 (n = 7)	-	8.6 ± 2.3 (n = 7)	10.9 ± 2.9 (n = 6)	11.6 ± 0.6 (n = 2)	11.1 ± 2.5 (n = 8)
	Range	8.0–15.1	12.7–13.1	8.0–15.1	6.7–11.2	8.0–11.8	6.7–11.8	3.8–8.8	7.9–11.9	3.8–11.9	3.8–10.6	-	3.8–10.6	5.8–14.4	11.1–12.0	5.8–14.4
CP %DM	Mean ± SD	20.8 ± 3.5 (n = 3.5)	17.0 ± 3.3 (n = 3)	20.6 ± 3.6 (n = 46)	21.4 ± 5.0 (n = 26)	18.6 ± 1.7 (n = 10)	20.6 ± 4.5 (n = 36)	19.5 ± 4.3 (n = 11)	20.2 ± 2.5 (n = 9)	19.8 ± 3.5 (n = 20)	22.5 ± 4.7 (n = 7)	14.7 ± 1.2 (n = 2)	20.7 ± 5.4 (n = 9)	19.8 ± 3.1 (n = 6)	15.3 ± 1.1 (n = 3)	18.3 ± 3.4 (n = 9)
	Range	11.3–30.1	13.6–20.1	11.3–30.1	10.4–34.6	14.9–21.1	10.4–34.6	15.0–26.5	16.1–24.0	15.0–26.5	13.3–27.5	13.8–15.5	13.3–27.5	15.3–24.6	14.1–16.3	14.1–24.6
NDF %DM	Mean ± SD	45.9 ± 11.1 (n = 50)	47.6 ± 5.5 (n = 3)	46.0 ± 10.9 (n = 53)	45.9 ± 9.7 (n = 25)	48.2 ± 7.1 (n = 11)	46.6 ± 9.0 (n = 36)	54.3 ± 4.5 (n = 11)	46.2 ± 3.5 (n = 7)	51.2 ± 5.7 (n = 18)	47.5 ± 8.9 (n = 6)	52.6 ± 1.1 (n = 2)	48.8 ± 7.9 (n = 8)	50.2 ± 6.5 (n = 6)	61.7 ± 5.7 9n = 2)	53.1 ± 7.9 (n = 8)
	Range	25.8–72.0	41.4–51.1	25.8–72.0	29.3–66.4	36.5–58.4	29.3–66.4	44.0–59.4	41.0–51.3	41.0–59.4	39.6–64.9	51.8–53.3	39.6–64.9	42.0–60.3	57.6–65.7	42.02–65.7
ADF %DM	Mean ± SD	31.8 ± 8.3 (n = 50)	27.9 ± 13.6 (n = 3)	31.6 ± 8.5 (n = 53)	33.5 ± 6.5 (n = 26)	36.6 ± 6.3 (n = 11)	34.5 ± 6.5 (n = 37)	30.8 ± 6.7 (n = 12)	36.1 ± 8.1 (n = 8)	32.9 ± 7.6 (n = 20)	37.3 ± 4.8 (n = 5)	38.3 ± 4.5 (n = 2)	37.6 ± 4.3 (n = 7)	41.2 ± 7.1 (n = 6)	35.1 ± 4.1 (n = 2)	39.7 ± 6.8 (n = 8)
	Range	14.7–49.5	13.7–40.9	13.7–49.5	21.6–46.0	27.1–48.2	21.6–48.2	24.2–47.3	24.4–46.3	24.2–47.3	31.9–43.9	35.1–41.4	31.9–43.7	35.6–55.0	32.2–38.0	32.2–55.0
ADL %DM	Mean ± SD	7.3 ± 3.4 (n = 47)	6.5 ± 2.4 (n = 3)	7.2 ± 3.3 (n = 50)	9.3 ± 3.0 (n = 20)	7.9 ± 3.3 (n = 11)	8.8 ± 3.2 (n = 31)	4.0 ± 1.9 (n = 11)	6.7 ± 1.7 (n = 8)	5.1 ± 2.2 (n = 19)	9.4 ± 1.5 (n = 5)	10.9 ± 1.8 (n = 2)	9.9 ± 1.6 (n = 7)	8.5 ± 2.0 (n = 5)	11.7 ± 2.6 (n = 2)	9.4 ± 2.5 (n = 7)
	Range	1.9–16.7	4.2–9.0	1.9–16.7	5.7–18.1	4.6–16.6	4.6–18.1	1.7–8.3	4.4–9.7	1.7–9.7	7.3–11.4	9.7–12.2	7.3–12.2	6.6–10.8	9.8–13.5	6.6–13.5
IVOMD %	Mean ± SD	73.3 ± 4.1 (n = 11)	-	72.7 ± 4.5 (n = 12)	70.5 ± 7.9 (n = 4)	66.3 ± 2.4 (n = 2)	69.1 ± 6.5 (n = 6)	50.5 ± 7.9 (n = 8)	-	51.2 ± 7.7 (n = 9)	60.5 ± 4.5 (n = 6)	-	58.5 ± 6.9 (n = 7)	-	-	-
	Range	68.9–79.5	-	65.8–79.5	64.6–82.0	64.6–68.0	64.6–82.0	42.2–68.7	-	42.2–68.7	55.0–64.9	-	46.1–64.9	-	-	-
ME MJ/kg DM	Mean ± SD	12.9 ± 2.0 (n = 30)	-	10.2 ± 0.66 (n = 12)	11.0 ± 1.1 (n = 15)	10.6 ± 1.3 (n = 3)	9.7 ± 0.73 (n = 6)	7.0 ± 1.2 (n = 8)	-	7.1 ± 1.2 (n = 9)	-	-	9.3 ± 0.85 (n = 7)	-	-	-
	Range	-	-	9.3–11.3	-	-	5.7–11.97	-	-	5.7–9.7	-	-	6.9–9.1	-	-	-

n: number of records, SD—standard deviation, DM—dry matter, CP—crude protein, NDF—neutral detergent fiber, ADF—acid detergent fiber, ADL—acid detergent lignin, IVOMD—in vitro organic matter digestibility, ME—metabolizable energy.

. Overall, the lowest ash content was recorded in Desmodium uncinatum (8.0 ± 2.3%), while Medicago sativa contained the highest ash content (11.8 ± 1.6%). The results also showed that the hay of herbaceous forage legume species had more ash compared to the fresh harvest. However, there was variation between fresh harvest and hay samples in CP content in all forage species; the observed difference was large in the two Desmodium species. Overall, data showed that, except for Desmodium uncinatum with a CP content of 18.2 ± 3.4%, the remaining herbaceous forage legumes contained similar and higher amounts of CP (Table 3). Among the studied species, Medicago sativa and Vicia species (46.0 ± 10.9% and 46.6 ± 9.0%, respectively) were determined to contain lower mean NDF, whereas Lablab purpurea and Desmodium uncinatum contained higher NDF of 51.2 ± 5.7% and 53.1 ± 7.9%, respectively. However, the differences in NDF, ADF, and ADL were not consistent between the two sample forms (fresh harvest and hay) across the selected herbaceous forage legume species, with the results showing greater fiber concentration in the hay samples for most species.

The IVOMD data of fresh harvest and hay were obtained only for Vicia species and calculated to have an IVOMD of 70.5 ± 7.9 and 66.3 ± 2.4%, respectively. Overall, the highest IVOMD was recorded in Medicago sativa forage (72.7 ± 4.5%). The ME concentration values followed a trend similar to that of the respective IVOMD data for all species (Table 3). Fresh forage of Medicago sativa had the highest ME (12.9 ± 2.0 MJ/kg DM), followed by fresh forage of Vicia species (11.0 ± 1.1 (MJ/kg DM), whereas the lowest record was determined in Lablab purpurea hay (7.0 ± 1.2 MJ/kg DM).

3.4. Nutritive Value of Selected Species from Multipurpose Fodder Tree/Shrubs

Table 4. Chemical composition and in vitro organic matter digestibility of selected species from multipurpose fodder tree/shrubs plants in Ethiopia.

Parameters		Cajanus cajan				Leucaena Species	Sesbania sesban	Tree lucerne
		* Foliage	Leaves	Twigs	Overall Mean	* Foliage	* Foliage	* Foliage
DM%	Mean ± SD	90.5 ± 2.0 (n = 13)	90.8 ± 2.4 (n = 6)	-	90.6 ± 2.1 (n = 19)	91.9 ± 4.0 (n = 10)	92.1 ± 1.9 (n = 13)	92.9 ± 1.4 (n = 14)
	Range	87.9–95.8	88.5–94.4		87.9–95.8	84.0–95.4	89.0–95.3	90.0–94.2
Ash (%DM)	Mean ± SD	8.8 ± 1.2 (n = 24)	7.8 ± 1.7 (n = 8)	-	8.6 ± 1.4 (n = 32)	9.3 ± 2.3 (n = 9)	10.4 ± 1.9 (n = 14)	6.3 ± 2.0 (n = 17)
	Range	6.7–11.1	5.1–10.1		5.1–11.1	6.2–13.8	6.3–13.7	4.3–11.1
CP (%DM)	Mean ± SD	21.1 ± 3.0 (n = 24)	23.4 ± 4.0 (n = 12)	18.5 ± 0.6 (n = 3)	21.6 ± 3.5 (n = 39)	21.8 ± 3.3 (n = 11)	23.6 ± 4.0 (n = 16)	22.0 ± 2.4 (n = 18)
	Range	17.5–30.4	17.0–30.9	18.1–19.2	17.0–30.9	14.9–27.6	15.3–30.6	16.2–25.1
NDF (%DM)	Mean ± SD	51.8 ± 7.7 (n = 24)	48.9 ± 7.8 (n = 12)	61.7 ± 2.3 (n = 3)	51.7 ± 8.0 (n = 39)	42.6 ± 16.5 (n = 9)	32.7 ± 11.3 (n = 15)	45.4 ± 12.1 (n = 18)
	Range	37.6–68.6	36.3–60.3	59.0–63.2	36.3–68.6	23.0–64.5	20.0–47.9	27.3–66.8
ADF (%DM)	Mean ± SD	36.6 ± 6.2 (n = 24)	33.1 ± 5.6 (n = 12)	43.2 ± 1.6 (n = 3)	36.1 ± 6.3 (n = 39)	29.7 ± 12.1 (n = 8)	25.2 ± 9.9 (n = 14)	27.4 ± 10.7 (n = 17)
	Range	18.7–45.9	28.7–47.5	41.5–44.6	18.7–47.5	14.0–45.7	13.1–40.1	17.8–48.8
ADL (%DM)	Mean ± SD	14.9 ± 5.5 (n = 18)	12.6 ± 1.3 (n = 4)	-	14.5 ± 5.1 (n = 22)	8.7 ± 2.6 (n = 8)	6.3 ± 2.7 (n = 12)	7.5 ± 1.4 (n = 15)
	Range	5.2–20.7	10.8–13.8	-	5.2–20.7	5.4–12.6	2.7–11.1	5.8–10.0
IVOMD (%)	Mean ± SD	51.9 ± 0.3 (n = 10)	61.0 ± 6.6 (n = 6)	49.6 ± 0.5 (n = 3)	54.4 ± 5.8 (n = 19)	70.9 ± 11.0 (n = 6)	73.0 ± 7.6 (n = 8)	52.6 ± 0.9 (n = 3)
	Range	51.6–52.6	51.3–68.9	49.1–50.1	49.1–68.9	62.2–92.4	63.3–87.3	51.9–53.6
ME (MJ/kg DM)	Mean ± SD	7.2 ± 0.1 (n = 10)	8.4 ± 0.8 (n = 7)	6.8 ± 0.1 (n = 3)	7.6 ± 0.8 (n = 20)	9.3 ± 1.1 (n = 6)	10.3 ± 0.6 (n = 6)	7.6 ± 0.5 (n = 7)
	Range	7.1–7.3	7.1–9.7	6.8–6.9	6.8–9.7	7.5–10.6	8.9–10.8	7.2–8.5

*: foliage represents edible portions (leaf, twigs, fine stem and reproductive parts) of Cajanus cajan, n: number of records, SD—standard deviation, DM—dry matter, CP—crude protein, NDF—neutral detergent fiber, ADF—acid detergent fiber, ADL—acid detergent lignin, IVOMD—in vitro organic matter digestibility, ME—metabolizable energy.

presents the chemical composition, in vitro organic matter digestibility, and ME concentration of prioritized species from the multipurpose fodder tree/shrub species. The selected species were the most commonly studied forage in Ethiopia for multiple uses, including animal feed sources. The selection of these species for individual analyses was based on the number of studies or records available. The results demonstrated that the foliage of tree lucerne had the lowest ash content (6.3 ± 2.0%), whereas the foliage of Sesbania sesban had the highest (10.4 ± 1.9%). From the overall mean, the analyzed species had high CP contents ranging from 21.6 ± 3.5% in Cajanus cajan to 23.6 ± 4.0% in Sesbania sesban (Table 4). Although the available data were limited to Cajanus cajan, there was a clear difference in protein values among different morphological fractions, where the lowest and highest CPs were determined in twigs and leaves (18.5 ± 0.6% vs. 23.4 ± 4.0%). Foliage of Sesbania sesban had minimum NDF (32.7 ± 13.4%), ADF (25.2 ± 9.9%), and ADL (6.3 ± 2.7%) contents, whereas Cajanus cajan had the greatest fiber concentration (51.7 ± 8.0% NDF, 36.1 ± 6.3% ADF, and 14.5 ± 5.1% ADL) among the multipurpose fodder tree/shrub species. Moreover, compared to the leaves and foliage, the twig parts of Cajanus cajan had higher NDF and ADF contents. There was no large variation in NDF and ADF concentrations between the Leucaena species and tree lucerne. Among the studied species, the foliage of Sesbania sesban had maximum IVOMD (73.0 ± 7.6%) followed by the foliage of Leucaeana species (70.9 ± 11.0%), with the minimum level of IVOMD recorded in Cajanus cajan and tree lucerne foliage (Table 4). The leaf portion of Cajanus cajan had better IVOMD values than twigs and whole foliage. Moreover, the ME concentration of the analyzed species showed a similar trend to the IVOMD results. From the overall mean value, Cajanus cajan and tree lucerne had similar ME contents (7.6 ± 0.8 and 7.6 ± 0.5 MJ/kg DM, respectively). The greatest ME level (10.3 ± 0.6 MJ/kg DM) was determined in Sesbania sesban.

3.5. Nutritive Values of Selected Species from Indigenous Browse Plants

The nutritive values (chemical composition and IVOMD) of common indigenous browse species in Ethiopia are reported in

Table 5. Chemical composition and in vitro organic matter digestibility values of common indigenous browse species in Ethiopia.

Parameters		Acacia asak	Acacia nilótica	Acacia saligna	Acacia seyal	Acacia tortilis	Balanites aegyptiaca	Cordia africana	Ficus thonningii	Grewia ferrugínea	Grewia tembensis	Millettia ferruginea	Prosofis juliflora	Rhus natelensis	Vernonia amygadalina	Ziziphus spina-christi
DM%	Mean ± SD	91.9 ± 2.1 (n = 4)	91.2 ± 1.7 (n = 5)	-	93.6 ± 2.4 (n = 4)	91.9 ± 0.8 (n = 5)	93.0 ± 2.8 (n = 6)	93.9 ± 2.6 (n = 11)	90.9 ± 1.2 (n = 5)	92.1 ± 3.1 (n = 3)	-	-	-	-	93.3 ± 2.2 (n = 9)	91.3 ± 1.9
	Range	90.1–94.6	89.0–93.5	-	91.0–96.8	91.0–92.7	90.0–97.3	90.7–98.2	89.5–92.5	89.4–95.5	-	-	-	-	89.0–95.5	89.7–94.4
Ash (%DM)	Mean ± SD	11.9 ± 4.3 (n = 4)	5.6 ± 2.2 (n = 7)	10.3 ± 2 (n = 12)	8.3 ± 1.6 (n = 5)	7.3 ± 1.7 (n = 11)	13.1 ± 3 (n = 9)	12.9 ± 2 (n = 10)	12.3 ± 5.1 (n = 6)	12.3 ± 3.1 (n = 5)	11.1 ± 5.1 (n = 6)	8.9 ± 3.7 (n = 5)	10.2 ± 2.5 (n = 5)	9.5 ± 1.6 (n = 6)	12.8 ± 1.9 (n = 14)	-
	Range	9.2–18.3	2.8–8.8	7.9–14.1	6.5–10.1	5.2–10.4	10.0–16.9	9.2–15.5	2.4–16.10	9.1–16.6	2.0–17.1	4.3–12.3	6.8–12.9	7.9–11.8	9.4–17.3	-
CP (%DM)	Mean ± SD	11.7 ± 5.5 (n = 4)	15.4 ± 1.4 (n = 7)	22.6 ± 3.6 (n = 12)	17.5 ± 3.5 (n = 8)	16.7 ± 3.8 (n = 10)	17.4 ± 3.4 (n = 10)	17.7 ± 4.3 (n = 13)	18.0 ± 4.5 (n = 7)	13.9 ± 4.6 (n = 5)	14.8 ± 4.2 (n = 6)	20.6 ± 4.0 (n = 5)	17.9 ± 6.2 (n = 6)	14.3 ± 4.1 (n = 10)	21.9 ± 5.1 (n = 15)	17.8 ± 4.5)
	Range	6.72–18.8	12.6–16.1	16.4–28.3	13.0–22.1	10.3–21.8	13.8–23.5	10.7–24.3	12.1–24.5	8.1–19.4	9.76–19.6	16.6–26.4	7.82–26.1	10.2–21.6	14.4–31.9	13.5–22.8
NDF (%DM)	Mean ± SD	45.1 ± 7.1 (n = 4)	26.7 ± 13 (n = 7)	33.4 ± 3.1 (n = 12)	29.9 ± 11.8 (n = 8)	31.7 ± 12.2 (n = 11)	35.1 ± 7.9 (n = 10)	52.7 ± 12.3 (n = 13)	51.8 ± 12.6 (n = 7)	48.9 ± 17.2 (n = 5)	54.1 ± 15.9 (n= 4)	49.3 ± 4.9 (n = 5)	36.4 ± 8.8 (n = 6)	38.9 ± 7.4 (n = 10)	42.2 ± 13.6 (n = 15)	35.5 ± 16.3
	Range	40.3–55.6	12.8–44.1	29.9–37.1	14.0–47.3	18.4–55.1	25.2–49.6	34.4–75.2	32.9–67.8	23.8–66.7	40.2–75.1	40.8–52.8	23.8–47.8	24.6–50.0	20.9–61.4	24.5–63.7
ADF (%DM)	Mean ± SD	25.1 ± 4.1 (n = 4)	22.5 ± 14.4 (n = 7)	28.7 ± 4 (n = 12)	20.1 ± 8 (n = 8)	22.8 ± 10 (n = 8)	21.0 ± 5.4 (n = 10)	36.7 ± 7.1 (n = 13)	37.8 ± 10.4 (n = 7)	29.4 ± 10.7 (n = 5)	26.0 ± 2.4 (n = 6)	33.4 ± 8.5 (n = 5)	28.7 ± 12.1 (n = 6)	26.7 ± 7.6 (n = 10)	30.2 ± 12.5 (n = 15)	21.3 ± 10.9
	Range	20.7–30.6	8.47–48.1	24.2–36.2	9.39–32.4	12.6–41.3	9.87–28.5	29.0–50.6	23.5–52.7	10.7–36.2	23.8–29.8	22.4–41.9	10.7–42.0	16.7–42.2	12.1–47.8	11.2–38.2
ADL (%DM)	Mean ± SD	8.2 ± 2.1 (n = 4)	8.8 ± 3.9 (n = 3)	3.9 ± 0.6 (n = 12)	9.4 ± 3.8 (n = 4)	9.4 ± 4.8 (n = 5)	10.6 ± 1.3 (n = 5)	17.3 ± 4.5 (n = 10)	14.5 ± 5.9 (n = 5)	13.8 ± 5 (n = 5)	10.1 ± 3.9 (n = 4)	12.4 ± 4.7 (n = 6)	9.6 ± 4.4 (n = 6)	13.7 ± 3.5 (n = 6)	14.4 ± 8.1 (n = 13)	10.3 ± 8.5
	Range	6.2–10.7	4.3–11.1	3.34–4.9	5.4–14.4	1.8–14.8	8.6–12.0	9.7–23.6	6.9–22.8	5.7–18.9	6.4–14.4	7.4–17.6	3.2–14.8	8.0–18.4	3.7–25.3	5.7–25.5
IVOMD (%)	Mean ± SD	-	55.5 ± 23.7 (n = 3)	66.1 ± 2.3 (n = 12)	63.2 ± 11.7 (n = 3)	53.8 ± 10.6 (n = 5)	51.0 ± 8.9 (n = 5)	59.0 ± 19.5 (n = 6)	70.0 ± 2.9 (n = 3)	-	-	46.8 ± 8.0 (n = 5)	46.8 ± 11.2 (n = 4)	61.0 ± 6.9 (n = 4)	55.5 ± 9.4 (n = 6)	-
	Range	-	34.1–81.0	62.9–70.5	51.5–74.9	44.1–72.0	38.6–60.4	33.7–82.8	67.3–73.2	-	-	39.7–60.5	33.2–59.6	51.0–67.0	41.4–65.0	-
ME (MJ/kg DM)	Mean ± SD	-	9.7 ± 3.5 (n = 3)	9.9 ± 0.4 (n = 12)	7.9 ± 0.35 (n = 3)	8.7 ± 1.2 (n = 4)	7.3 ± 1.2 (n = 5)	8.6 ± 0.76 (n = 3)	7.3 ± 2.8 (n = 2)	-	-	7.1 ± 1.2 (n = 4)	7.3 ± 1.4 (n = 3)	8.7 ± 0.4 (n = 5)	7.2 ± 1.7 (n = 7)	8.2 ± 1.1
	Range	-	7.3–12.2	9.4–10.6	7.7–8.2	7.0–9.9	5.6–8.6	7.8–9.3	5.3–9.3	-	-	5.8–8.4	5.7–8.3	8.1–9.1	7.4–9.0	7.4–9.0

n: number of records, SD— standard deviation, DM—dry matter, CP—crude protein, NDF—neutral detergent fiber, ADF—acid detergent fiber, ADL—acid detergent lignin, IVOMD— in vitro organic matter digestibility, ME—metabolizable energy.

. The mean minimum and maximum ash contents of selected indigenous browse plant species were determined in the foliage of Acacia nilotica (5.6 ± 2.2%) and Balanites aegyptiaca, (13.1 ± 3.0%), respectively. Moreover, comparable CP contents were recorded in some species, such as Acacia seyal, Balanites aegyptiaca, Cordia africana, and Prosopis juliflora. The largest CP values were calculated for Millettia ferruginea (20.6 ± 4.0%), Vernonia amygadalina (21.9 ± 5.1%), and Acacia saligna (22.6 ± 3.6%) (Table 5). Meanwhile, the results revealed that Acacia asak contained the lowest mean CP of 11.7 ± 5.5% among the indigenous browse species, although there was a big variation between the minimum (6.72%) and maximum (18.8%) values. The neutral detergent fiber content of Acacia species ranged from 26.7 ± 13% for Acacia nilotica to 45.1 ± 7.1% for Acacia asak. Overall, the selected acacia species had ADF and ADL contents ranging from 20.1 ± 8% to 25.1 ± 4.1% and from 3.9 ± 0.6% to 9.4 ± 33.8%, respectively. Among the other indigenous browse species analyzed, Balanites aegyptiaca and Grewia tembensis contained the minimum (35.1 ± 7.9%) and maximum (54.1 ± 15.9%) NDF concentrations. On the other hand, Ficus thonningii had the highest ADF (37.8 ± 10.4%), while Balanites aegyptiaca had the lowest ADF (21.0 ± 5.4%). Cordia africana contained the highest ADL concentration, with a value of 17.3 ± 4.5% (Table 5).

The IVOMD was greatest in Ficus thonningii (70.0 ± 2.9%), followed by Acacia saligna (66.1 ± 2.3%), Acacia seyal (63.2 ± 11.7%), and Rhus natelensis (61.0 ± 6.9%). Contrarily, the lowest IVOMDs were recorded in the foliage of Millettia ferruginea and Prosopis juliflora (46.8 ± 8.0–46.8 ± 11.2%, respectively). The greatest withing species variability in IVOMD values was recorded for acacia species, Acacia nilotica (34.1–81.0%), and Cordia africana (33.7–82.8%). Compared to the herbaceous forage legumes and multipurpose fodder species, there was greater variability in ME concentration among the indigenous browse species (Table 5). The ME values of the browse species varied from 7.1 ± 1.2 to 9.9 ± 3.5 MJ/kg DM, with Millettia ferruginea and Acacia saligna having the minimum and maximum values, respectively. Compared to between species, within-species variabilities in ME values were large in most species.

3.6. Tannin Contents of Selected Indigenous Browse Species and Forage Legumes

The condensed tannin profiles of selected browse species and forage legumes are presented in

Table 6. Condensed tannin concentration of selected indigenous browse species and forage legumes in Ethiopia.

Forage Species	Forage Category	Unit	Condensed Tannin
			Mean	Range
Desmodium intortum	Herbaceous forage legume	CT ab/g NDF	64.4	54.1–78.6
Cajanus cajan	Multipurpose fodder tree/shrub	CT ab/g NDF	4.62	2.29–7.77
Sesbania sesban	Multipurpose fodder tree/shrub	CT ab/g NDF	82.65	48.90–121.10
Tree lucerne	Multipurpose fodder tree/shrub	CT ab/g NDF	10.22	8.76–11.68
Acacia asak	Indigenous browse species	CT ab/g NDF	100.30	98.6–102
Acacia nilotica	Indigenous browse species	g/kg DM	80.57	14.7–114.9
Acacia seyal	Indigenous browse species	g/kg DM	121.97	34.0–211
Acacia tortilis	Indigenous browse species	CT ab/g NDF	184.65	30.0–332
Albizia amara	Indigenous browse species	CT ab/g NDF	84.5	82.5–86.5
Balanites aegyptieca	Indigenous browse species	g/kg DM	19.13	1.20–92.0
Cordia africana	Indigenous browse species	g/kg DM	9.23	3.0–13.4
Dichrostmachys cinerea	Indigenous browse species	CT ab/g NDF	29.6	27.6–31.6
Ficus thonningii	Indigenous browse species	g/kg DM	5.42	5.20–5.64
Grewia bicolour	Indigenous browse species	g/kg DM	123.35	111–136
Grewia tembesis	Indigenous browse species	g/kg DM	40.6	2.00–79.2
Millettia ferruginea	Indigenous browse species	g/kg DM	17.55	5.37–33.0
Prosofis juliflora	Indigenous browse species	g/kg DM	44.24	0.10–111
Rhus natelensis	Indigenous browse species	g/kg DM	176.17	78–254
Vernonia amygadalina	Indigenous browse species	g/kg DM	3.68	2.00–4.79
Ziziphus spina christi	Indigenous browse species	CT ab/g NDF	47.7	32.0–57.9

. Available data showed that species, such as Acacia asak (100 g/kg DM), Acacia seyal (122 g/kg DM), Acacia tortilis (185 ab/g NDF), Grewia bicolor (123 g/kg DM), and Rhus natalensis (176.2 g/kg DM) contained a high amount of condensed tannins (CT). On the other hand, species, such as Balanites aegyptiaca, Cordia africana, Ficus thonningii, Millettia ferruginea, and Vernonia amygadalina, contained low levels of tannins, ranging from 3.68 to 19.1 g/kg DM. Moderate concentrations of tannins were reported for some indigenous browse species, including Dichrostachys cinerea, Albizia amara, Grewia tembesis, Prosopis juliflora, and Ziziphus spina-christi (Table 6). Similar to browse species, some herbaceous forage legumes contained tannins of different types and concentrations. Two Desmodium species (Desmodium intortum and Desmodium uncinatum) are tannin-rich herbaceous forage legumes adapted to tropical environments. Desmodium intortum had a CT value of 64.4 Abs/g NDF. Among the multipurpose fodder tree/shrub species, Cajanus cajan and tree lucerne contained a low concentration of CT, whereas the Sesbania sesban foliage contained a higher CT concentration of 82.65 Abs/g NDF (Table 6).

3.7. Description of Animal Experiments Included in In Vivo Database

Statistical descriptions of the studies included in the in vivo database are summarized in

Table A1. Nutrient composition of the basal diets used in the studies included in in vivo database.

Variables	Crop Residues (n = 13)		Cultivated Grass Hay (n = 9)		Natural Pasture Hay (n = 40)		Overall Mean (n = 61)
	Mean ± SD	Range	Mean ± SD	Range	Mean ± SD	Range	Mean ± SD	Range
DM%	84.1 ± 13.0	55.0–94.8	85.7 ± 19.0	25.8–96.0	91.9 ± 2.3	87.0–95.8	89.2 ± 10.8	25.8–96.0
Ash%	8.8 ± 2.2	4.0–11.7	9.9 ± 2.6	5.1–14.8	9.7 ± 1.6	6.6–12.3	9.6 ± 2.0	4.0–14.8
CP%	6.2 ± 1.9	3.2–10.2	7.6 ± 2.7	2.8–12.2	6.9 ± 1.5	3.2–10.2	6.9 ± 2.0	2.8–12.2
NDF%	74.8 ± 9.6	52.8–84.2	67.4 ± 8.9	46.2–77.2	70.7 ± 9.6	41.0–89.9	70.7 ± 9.6	41.0–89.9
ADF%	52.7 ± 8.9	37.9–64.4	41.9 ± 10.3	17.3–53.3	46.6 ± 8.0	30.2–68.4	46.6 ± 9.2	17.2–68.4
ADL%	12.7 ± 8.9	5.4–30.7	7.0 ± 5.4	2.7–19.0	9.9 ± 4.6	4.3–22.2	10.0 ± 5.9	2.7–30.7

n: number of studies, SD—standard deviation, DM—dry matter, CP—crude protein, NDF—neutral detergent fiber, ADF—acid detergent fiber, ADL—acid detergent lignin.

and

Table A2. Summary of selected characteristics of the studies included in in vivo database.

Variables	N	Mean	SD	Minimum	Maximum
Initial body weight of animals (kg)	61	17.8	3.43	11.5	28.4
Supplementation level g/day	47	277.5	101.4	100	588
Substitution level of concentrate with foliage (%)	26	47.9	18.3	15	82.8
Proportion of foliage in the total diet (%)	45	31.9	11.4	8.4	64.5
Nutrient content
Basal diet CP (%DM)	61	6.9	1.9	2.8	12.2
Foliage CP (%DM)	48	19.8	4.7	7.4	30.0
Concentrate CP (%DM)	35	22.2	7.1	16.0	45.3
Basal diet NDF (%DM)	61	70.1	9.3	41.0	89.9
Foliage NDF (%DM)	48	41.2	12.2	13.2	68.8
Concentrate NDF (%DM)	35	41.9	10.2	23.5	69.3

N: number of studies, DM—dry matter, CP— crude protein, NDF—neutral detergent fiber; SD—standard deviation.

. The studies included in the database used between four and eight animals per treatment. On average, the initial body weight of experimental animals was 17.8 ± 3.43 kg (ranging from 11.5 kg to 28.4 kg). Natural pasture hay (n = 40, 64.5%), cultivated grass hay (n = 13, 21%), and crop residues (n = 9, 14.5%) were the major roughage feedstuffs used as a source of basal diets. The database exhibited large variations in several characteristics of the included animal experiments, including forage types, supplementation level, proportion of the foliage supplement in the total diet consumed by animals, level of concentrate feed supplement being replaced by the forage, and the nutritional composition of both the basal diets and supplements (forage and concentrate feeds) (Table A2).

The included studies used a mean supplementation level of 277.5 ± 101.4 g/kg DM head daily using sole forage, whereas most studies supplemented between 100 g and 588 g foliage in on a daily basis per head. On average, the forage supplement constituted about 31.9 ± 11.4% of the total diet consumed by animals on a DM basis. In studies that evaluated the partial and full substitution of concentrate feed mixes with the foliage of browse species and forage legumes, the data revealed that, on average, up to 47.9 ± 18.3% (ranging from 15% to 82.8%) concentrate feed supplement was replaced by forage successfully (Table A2).

The roughage feedstuffs used as a basal diet contained 6.9 ± 1.9% CP, 70.7 ± 9.3% NDF, 45.3 ± 9.6% ADF, and 10.0 ± 5.9% ADL. Compared to the CP content, the fiber content varied significantly, as shown by a high standard deviation or wide range between the maximum and minimum values. Basal diets were offered ad libitum in all studies, and ad libitum feeding of basal diet applied as a control diet with no supplementation in some studies. On the other hand, on average, the foliage studied for supplement purposes had a CP, NDF, and ADF of 19.8 ± 4.9%, 41.2 ± 12.2%, 28.1 ± 10.9%, respectively. The forage had a comparable NDF but slightly lower CP content and higher ADF and ADL content than concentrate feed mixes included as supplements.

3.8. Nutrient Utilization and Animal Performance

3.8.1. Feed Intake and Apparent Digestibility

Table 7. Least square effects (LSM ± SE) of forage supplementation on nutrient digestibility, feed intake, and production parameters of ruminants fed low-quality basal diet.

Variables	N	Control Treatment	Forage-Supplemented Treatment	p-Value	AIC	RMSE	Covariable
Apparent digestibility
DM%	15 (55)	55.3 ± 1.9	63.6 ± 1.8	<0.0001	339.8	4.06	-
CP%	15 (54)	54.7 ± 3.2	67.6 ± 2.9	<0.0001	372.8	6.64	-
NDF%	15 (55)	56.3 ± 2.1	62.7 ± 1.7	0.0015	372.1	6.259	-
Intake parameters							Body weight
DMI (g)	26 (91)	547.2 ± 21.3	692 ± 18.2	<0.0001	1046.9	66.37	<0.0001
CPI (g)	24 (85)	49.0 ± 4.3	83.6 ± 3.6	<0.0001	716.5	14.05	0.0005
NDFI (g)	21 (78)	377.8 ± 18.8	420.8 ± 17.8	<0.0001	834.9	40.06	0.0430
MEI (MJ)	7 (23)	4.95 ± 0.71	7.11 ± 0.70	<0.0001	66.4	0.620	0.2068
Production Parameters
ADG (g)	26(95)	11.6 ± 5.47	40.3 ± 4.99	<0.0001	831.8	14.84	-
FCE (g ADG/g DMI)	26 (95)	0.011 ± 0.006	0.051 ± 0.006	<0.0001	−417.3	0.0153	-
Carcass DP	10 (33)	44.2 ± 2.3	48.9 ± 2.3	0.0218	164.0	1.44	-

N: number of studies (number of records), DMI—dry matter intake, CPI—crude protein intake, NDFI—neutral detergent fiber intake, MEI—metabolizable energy intake, ADG—Average daily gain, FCE—feed conversion efficiency, DP—dressing percentage, RMSE—residual mean square error and AIC—Akaike’s information criterion.

and

Table 8. Least square effects (LSM ± SE) of forage supplementation compared to concentrate feeds on nutrients digestibility, feed intake, and production parameters of ruminants fed low-quality basal diet.

Variables	N	Forage Supplemented Treatment	* Forage-Concentrate Supplemented Treatment	Concentrate Supplemented Treatment	p-Value	RMSE	AIC	Covariable
Apparent digestibility
DM%	11 (48)	b 62.6 ± 2.4	a 65.7 ± 2.3	a 66.4 ± 2.4	0.0035	2.66	278	-
CP%	11 (51)	c 62.0 ± 3.4	b 67.2 ± 3.1	a 71.1 ± 3.4	0.0005	5.15	334	-
NDF%	11 (51)	c 55.4 ± 2.5	b 60.7 ± 2.4	a 64.8 ± 2.5	<0.0001	3.82	306.1	-
Intake parameters								Body weight
DMI (g/d)	25 (109)	701.7 ± 25.6	729.0 ± 23.4	717.8 ± 23.9	0.2347	32.31	1081.7	0.0237
CPI (g/d)	29 (107)	88.6 ± 5.1	95.0 ± 4.7	96.3 ± 4.8	0.0733	6.90	884.3	0.0179
NDFI (g/d)	27 (114)	b 387.8 ± 15.9	a 411.5 ± 15.1	a 409.0 ± 15.2	0.0322	21.05	1135.3	0.0041
MEI (MJ/d)	7 (32)	b 7.01 ± 0.48	a 7.79 ± 0.45	a 7.92 ± 0.47	0.0027	0.49	71.3	0.4273
Production parameters
ADG (g/d)	17(76)	b 38.2 ± 6.5	a 53.9 ± 5.9	a 50.3 ± 6.1	0.0035	7.73	609.1	-
FCE (g-ADG/g DMI)	16(72)	0.057 ± 0.008	0.069 ± 0.008	0.069 ± 0.008	0.0685	0.0072	−363.4	-
Carcass DP	10(44)	50.8 ± 1.6	51.5 ± 1.4	51.0 ± 1.5	0.7011	2.15	216.9	-

* Substitution level of concentrate by forage in analyzed studies: 47.58% (16–82.8%), Values with different superscripts (^a–^c) across columns are significantly different at p < 0.05. N: number of studies (number of records), DM—dry matter, DMI—dry matter intake, CP—crude protein, CPI—crude protein intake, NDF—neutral detergent fiber, NDFI—neutral detergent fiber intake, MEI—metabolizable energy intake, ADG—average daily gain, FCE—feed conversion efficiency, DP—dressing percentage, RMSE—residual mean square error, and AIC—Akaike’s information criterion.

present the feed intake and apparent nutrient digestibility results of the two separate meta-analyses conducted to compare forage supplementation against control without supplements and concentrate feed-based supplements, respectively. The result showed that DMI, CPI, and MEI increased significantly (p < 0.05) from 547.2 ± 21.3 to 692 ± 18.2 g/d, from 49.0 ± 4.3 to 83.6 ± 3.4 g/d, and from 4.95 ± 0.71 to 7.11 ± 0.7 MJ/day, respectively, following the inclusion of forage to the diets based on ad libitum feeding of basal diets. A comparison of forage supplementation with concentration-based supplementations showed similar (p > 0.05) DMI among sole forage, sole concentrate feed, and concentrate feed partially substituted by forage-supplemented treatments. A significant variation (p < 0.05) among these dietary supplements was observed in their CPI, NDFI, and MEI. Animals fed sole forage supplement had a lower CPI (88.6 ± 5.1 g/d) and MEI (7.01 ± 0.45 MJ/d) than the animals fed sole concentrate and concentrate partially substituted with the forage-supplemented treatments (CPI: 95.0 ± 4.7 to 96.3 ± 4.8 g/d and MEI: 7.79 ± 0.45 to 7.92 ± 0.47 MJ/d (Table 8).

The impacts of forage supplementation on the apparent digestibility of nutrients were consistent with the effects observed on the nutrient intake. As shown in Table 6, the inclusion of forage as a supplement increased the apparent digestibility of DM from 55.3 ± 1.9% to 63.6 ± 1.8% (p < 0.0001), CP from 54.7 ± 3.2% to 67.6 ± 2.9% (p < 0.0001), and NDF from 56.3 ± 2.1% to 62.7 ± 1.7% (p < 0.0015). Nevertheless, sole forage supplementation had reduced effects on the apparent nutrient digestibility of DM, CP, and NDF than concentrate feed-based supplementation treatments (Table 7). In contrast, the dietary treatment containing concentrate feed partially substituted with forage exhibited similar (p > 0.05) responses to the apparent digestibility of DM with sole concentrate feed supplement but lower digestibility of CP (67.2 ± 3.1% versus 71.1 ± 3.4%) and NDF (60.7 ± 2.4% vs. 64.8 ± 2.5%). Overall, it appeared that the digestibility of nutrients tended to decrease when the concentrate feed was substituted with an increasing level of forage.

3.8.2. Production Responses

The average daily gain (ADG), feed conversion efficiency (FCE), and carcass dressing percentage on an empty body weight basis were analyzed to determine the effects of foliage supplementation on the production responses of the animals. In both analyses, ADG and FCE tended to respond in a similar trend to the nutrient utilization variable response (Table 6 and Table 8). Animals fed a foliage-supplemented diet had significantly higher (p < 0.0001) ADG than the control treatment without supplement (37.5 ± 4.8 g/d and 11.2 ± 5.1 g/d, respectively, Table 6). Table 7 presents data comparing different supplementation strategies, and the results show significant differences (p < 0.0035) among the treatments in the ADG. The sole foliage-supplemented group (38.2 ± 6.5 g/d) had lower weight gain performance than sole concentrate supplement and concentrate partially substituted by foliage treatments (50.3 ± 5.9 g/d and 53.3 ± 3.45 g/d, respectively). Compared with the control treatment with no supplement, sole foliage supplementation resulted in a significant improvement in FCE (0.010 ± 0.006 versus 0.050 ± 0.006, Table 7). Moreover, the result shows that animals fed sole foliage-supplemented treatments demonstrated similar FCE (p = 0.0685) to animals receiving concentrate containing supplementary diets in both forms. Similar to FCE, the carcass dressing percentage was improved significantly (p = 0.0085) by foliage inclusion as a supplement compared to the control with no supplement (44.0 ± 2.3% vs. 48.9 ± 2.2%, Table 7). There was no significant difference (p > 0.05) among the three supplementation strategies tested on the carcass dressing percentage (Table 8).

4. Discussion

4.1. Nutritional Importance of Browse Species and Forage Legumes

Browse species have an important contribution to the supply of feeds for ruminants, either in the form of in situ browsing or feeding on harvested leaves, pods/fruits, and other edible portions of the plants. Indigenous browse species include shrubs and trees, which are essential components of natural communities, such as shrublands and woodlands, and are known as native or spontaneous species [27]. This class of plant community was the predominant one in the nutritional characterization of forages in Ethiopia. The large number of indigenous browse species analyzed in this study (about 148 species, Table 1) provides good evidence that Ethiopia is endowed with diverse flora of indigenous browse trees and shrubs of immense ecological and socioeconomic values [28]. Mengistu et al. [9] reported that about 179 browse species from 51 genera have already been registered in the country, of which 51 species from 31 genera are promising browse species. It has been well documented that the indigenous browse species play vital roles in nutrient supply for livestock [29,30,31], and the importance further increases during the dry period when herbaceous forages dry off [32]. According to Atsbha and Wayu [32], leaves, pods, twigs, and fruits are the plant parts that are utilized by domesticated animals widely in Ethiopia. Foliage of browse species is either utilized in situ by animals browsing or cut and fed to the animals.

In the current analysis (Table 1), Acacia species were identified as the dominant and more diverse species. Acacia is a leguminous plant family that is widely adapted and distributed in arid and semiarid regions. It can produce high-quality feed rich in protein, and supplementation of ruminants with acacia leaves and pods/fruits can improve animal production performance [33]. However, some species contain some antinutritional compounds, mainly in the form of tannins [34], and in some areas, farmers practice postharvest interventions, such as wilting before feeding, to overcome the palatability problem associated with the presence of tannins [31]. Furthermore, species, such as Cordia africana, Vernonia amydalina, Ficus thonningii, and Rhus natelensis, have been examined in many studies reporting the nutritional values of browse species in Ethiopia. Indigenous browse species have multiple values and merits for smallholder farmers. Good nutritional value, palatability, and high biomass production are highly valued and preferred attributes of indigenous browse species by farmers [35,36]. Ficus species, such as Ficus thonnings (local name; Chibha), are examples of indigenous browse plants with good biomass production [37,38]. Mengistu et al. [37] developed a full production package for the integration of Ficus thonnings into livestock feed production in Ethiopia.

Research efforts have been made to identify and popularize forage legumes of different types, such as herbaceous forages (annual, biennial, and perennial types) and woody/shrub types, using both indigenous and exotic species in Ethiopia. High yields of better-quality forage, efficiency in biological nitrogen fixation (BNF), and adaptation to diverse agro-climatic variations and climate change are the main attributes of forage legumes [39]. However, more than one species was cumulatively mentioned under the forage Vetch (Vicia species) and Leucaena species, and, hence, 17 species commonly studied in Ethiopia from herbaceous forage legumes and multipurpose fodder tree/shrub species were included in the current analysis (Table 1). Woody and shrub-type forage legumes are included in the category of multipurpose fodder tree/shrub species in the analysis. The widely popularized multipurpose fodder tree/shrub species in Ethiopia include sesbania (Sesbania sesban), tree Lucerne (Chamaecytisus palmensis), Leucaena (Leucaena leucocephala, Leucaena pallida, and Leucaena diversifolia), and pigeon pea (Cajanus cajan). According to Franzel et al. [16], multipurpose fodder trees are particularly important in the highlands of East Africa as a feed source. Some multipurpose fodder tree species (e.g., Sesbania sesban) have good acceptability as a source of protein supplement for ruminants [17]. Farmers have reported that feeding Sesbania leaves can increase weight gain, milk production, and reproductive efficiency in animals. Moreover, in addition to protein-rich feed supply, multipurpose fodder tree/shrub species have the capacity to maintain soil fertility and health through atmospheric nitrogen fixation, prevention of soil erosion, and mulching purposes, which subsequently contribute to an increase in overall agricultural productivity and income for farmers [18,40]. Most documented multipurpose fodder tree/shrub species are also characterized with a high DM yield reported to be 10–12 tons/ha compared to the 3–5 tons/ha of herbaceous forage legumes [9]. Despite the known merits and potential of multipurpose tree/shrub species for domestic ruminants, their adoption and production rate under smallholder farmers still remain quite low. The limited availability of species appropriate to different agroecological zones, shortage of seed supply, and awareness gaps among farmers are major constraints that challenge the uptake of improved fodder tree/shrub species [16]. Thus, initiatives for the promotion of multipurpose fodder tree/shrub species for successful integration into different farming systems to fill feed shortage gaps should be supported. This will enable full exploitation of the merits of multipurpose fodder tree/shrub species in mitigating the current feed gaps.

Large genetic resources of promising species and varieties of herbaceous forage legumes have been studied in Ethiopia. In this analysis, forage vetch species, including Vicia atropurpurea, Vicia dasycarpa, Vicia narbonensis, Vicia sativa, and Vicia villosa, were collectively evaluated. Similarly, the nutritional value of Medicago sativa (alfalfa), Lablab purpurea, and Desmodium species was included in the analysis. In Ethiopia, 358 herbaceous forage types, including 42 leguminous types, have been documented already [9]. Among these genetic resources, 58 species (from 31 genera) were claimed to have high potential for forage and pasture production. In addition, more than twenty improved forage legume varieties belonging to ten species from seven genera have been characterized and registered for improved forage production [39]. Despite notable progress in both varietal development and nutritional analysis of leguminous forage species, their adoption and utilization rates remain relatively low. Therefore, a crucial step towards fully exploiting their potential in livestock feed supply involves the systematic integration of cultivated forage legumes into the current feed production niche [11,19].

4.2. Chemical Composition

The nutritional value of browse trees, shrubs, and forage legumes in Ethiopia has been characterized using their chemical composition and in vitro digestibility. However, a larger amount of data was collected from the literature on ash, CP, NDF, ADF, and ADL content compared to the digestibility and energy value. The large numbers of species evaluated and reported for their nutritive value make it difficult to complete individual species-based analysis. Therefore, all the reported species were categorized into herbaceous forage legumes, multipurpose fodder tree/shrub species, and indigenous browse species. The nutritive values of aboveground biomass of herbaceous forage legumes harvested at the vegetative versus blooming stage and different morphological fractions for multipurpose fodder tree/shrubs and indigenous browse species are summarized (Table 2). Despite these breakdowns during data analysis and categorization of the species, there were larger variations in the nutritive value within the forage category and species (range values) than between forage categories and species. However, the values varied between morphological fractions; multipurpose fodder trees/shrubs had higher CP (22.8 ± 3.2%) than herbaceous legumes (20.3 ± 3.7%) and indigenous browse species (17.6 ± 4.8%). The current result is consistent with a previous study reporting higher CP in multipurpose tree species (21.6–27.8%) than in herbaceous forage legumes such as Lablab forage (18.0%) in Ethiopia [41]. The relatively lower CP content in indigenous browse species compared with other categories might be due to the pooling of both leguminous and non-leguminous plant species for ease of analysis. Non-legume browse species have a lower protein content than browse species from leguminous plant families [42]. Moreover, the nutritional analysis of tree species involves sampling of leaves, twigs, and fine stems, which potentially contributes to the higher protein concentration in fodder trees than in herbaceous plants, which are harvested as the whole aboveground biomass [43].

Furthermore, the data were analyzed for selected species from each forage category based on the number of reports/studies available. Similarly, the chemical composition of individual species varied between and within species. Herbaceous forage legumes analyzed in hay form contain lower CP than fresh harvest, which might be attributable to the loss of leaf portion during cuing process (Table 3). Furthermore, factors, such as differences in the studied cultivars, maturity stage, growing agroecology, and others, could also be prominently attributed to the large variation. All analyzed herbaceous forage legumes and multipurpose fodder tree/shrub species have good nutritional value, being rich in protein. Except for Desmodium uncinatum, which had the lowest CP content of 18.2 ± 2.9%, the other forage legumes from both herbaceous and multipurpose fodder tree/shrub species had CP contents above 19%. This value was defined as an indicator of good-quality roughage for forage (including legumes, grass, and legume–grass mixtures) for ruminants. Among indigenous browse species, only Acacia saligna, Millettia ferruginea, and Vernonia amygadalina exhibited CP levels exceeding 19% (Table 5). This analysis showed comparable protein contents in species, like Acacia seyal, Balanites aegyptiaca, Cordia africana, and Prosopis juliflora. Moreover, the chemical composition of indigenous browse species in the current study is in agreement with the findings of Ondiek et al. [44], who reported CP contents ranging between 11.7% and 24.9% for Acacia species of Kenyan rangelands.

The protein content of the forages serves as a crucial source of nitrogen for rumen microorganisms and amino acids for host animals in ruminant nutrition [45]. Protein is the most deficient nutrient in many tropical feedstuffs, significantly affecting animal productivity. Hence, most nutritional analyses of browse species and forage legumes were targeted to identify species with sufficient protein content for use in the supplementary diet of ruminants. It is widely cited that a CP above 7% is required in ruminant diets to support optimal rumen microbial growth and activity levels, below which voluntary feed intake could be adversely affected [46]. Based on the results, all analyzed species in their different harvesting stages and forage forms for herbaceous forage legumes and morphological fractions for multipurpose fodder tree/shrub and indigenous browse species had sufficient protein for ruminant feeding. Studies have also estimated that a dietary CP content above 15% or 150 g/kg DM is required to meet the protein requirements of lactating dairy cattle. Thus, except for a few species, such as Acacia asak (11.7 ± 5.5%), Grewia ferruginea (13.9 ± 4.6%), Grewia tembensis (14.8 ± 4.2%), and Rhus natelensis (14.3 ± 4.1%), the analyzed indigenous browse species had sufficient CP to meet the protein requirements of lactating animals. Additionally, all studied species have protein values that can meet the maintenance requirement for CP, which is 10% [47]. Considering their protein values, the selected species can serve as protein supplements for high-producing dairy cows or young growing livestock, in the absence of other sources [47].

The analysis of fiber content based on the concentrations of NDF, ADF, and ADL showed that forage from herbaceous forage legumes contained more fiber than browse species, particularly when harvested at the blooming stage and conserved in the form of hay (Table 2). Nevertheless, the ADL content of herbaceous forage legumes was comparable with multipurpose fodder tree/shrub species, in which both have a lower concentration (Table 3 and Table 4). The practice of harvesting whole aboveground biomass for nutritional analysis and animal feeding purposes could result in a high concentration of structural carbohydrates in forage from herbaceous categories. This was because of the high proportion of stems in the final harvest. The overall data for the forage categories and selected species across forage categories showed that cultivated forage legumes and indigenous browse species in Ethiopia have fiber concentrations lower than the values reported for tropical grasses [48] and natural pasture hay and crop residue produced in Ethiopia [10]. Based on a study by Meissner et al. [49], an NDF content of 600 g/kg (60%) is the optimum tolerable level of fiber in tropical forages used for ruminant feeding, and concentrations exceeding this amount could negatively affect voluntary feed intake. Nonetheless, based on the determined mean values, all evaluated species had low to moderate fiber concentrations. The reported results between minimum and maximum content in the range values demonstrated that the value of fiber content varied largely within the same species, which was partly attributable to study variation. Forage legumes with NDF and ADL levels below 40% and 31%, respectively, could provide good-quality roughages sources. Sesbania and all acacia species, except Acacia asak, Balanites aegyptiaca, Prosopis juliflora, Rhus natelensis, and Ziziphus spina-christi, possess NDF and ADL levels below these suggested thresholds. In this regard, herbaceous forage legumes exhibited a higher fiber content (>40% NDF and >31% ADF). In comparison with herbaceous forages and multipurpose fodder species, there were large variations in the chemical compositions of the indigenous browse species included.

In addition to the variation among forage categories and forage species, the current literature highlights a significant variation in the chemical composition of forage reported in different studies. The nutritional composition of forage is generally influenced by various biotic and abiotic factors. The data generated suggest that variations among the included studies can be attributed significantly to factors, such as differences in the species and variety, agroecology, harvesting stage, plant components, and sample processing techniques. A nutritional analysis by Derero and Kitaw [42] revealed that browse species from leguminous plant families exhibit superior nutritional value compared to non-leguminous browse species. The primary reason for the high protein content of leguminous plants is their ability to fix atmospheric nitrogen, which results in a subsequent increase in nitrogen uptake and accumulation in plant parts.

Importantly, forage legume cultivar studies in Ethiopia have shown significant effects of cultivar differences on the chemical composition of Medicago sativa [50,51,52,53,54], Lablab purpurea [55], Cajanus cajan [56,57,58], and Vicia species [58,59,60]. In addition, the effects of the morphological components of plants [61,62,63,64], seasonal variations [65,66,67] and the agroecology or altitude of sampling areas [34,66] on the nutritive values of indigenous browse species and cultivated forage legumes were investigated. A nutritional assessment conducted by Feyisa et al. [10] revealed an increasing trend in protein content during the wet season compared to the dry season, with contrasting responses observed for fiber accumulation. Notably, plant biomass with a higher proportion of leaves over stems demonstrated better nutritive value. Additionally, factors, such as the stage of maturity, postharvest processing and storage conditions, variability in moisture content, temperature, sunlight exposure, and soil fertility, exert a significant influence on the nutritive value of forage materials [68,69]. Hence, the large variations recorded in the browse species studied in Ethiopia might be attributable to the multitude of factors determining nutrient concentrations.

4.3. In Vitro Organic Digestibility and Metabolizable Energy Value

The highest IVOMD values recorded in forage at the vegetative stage and leaves could be due to their relatively higher protein content and lower fiber concentration. From overall mean values, multipurpose fodder tree/shrub species and indigenous browse species had comparable IVOMD values. From the data analyzed based on individual species, the greatest mean values of IVOMD were recorded in Medicago sative and Vicia species (Table 3) from herbaceous forage legumes and Leucaena trees and Sesbania sesban foliage (Table 4) in multipurpose fodder tree/shrub species. Similarly, greatest IVOMD values were determined in the foliage of Ficus thoninigii from indigenous browse species (Table 5). The determined IVOMD values for these species are comparable with a previously reported IVOMD ranging from 67.9 to 92.4% for selected forage legumes of herbaceous and woody/shrub types from the Rift Valley area of Ethiopia [70]. According to the assessment of Feyisa et al. [10], forage legumes with digestibility values exceeding 70% are generally of good nutritional quality to be utilized as protein supplements in low-quality roughage (crop residues and natural pasture hay)-based diets of ruminants. On the other hand, Owe and Jauasuriya [71] concluded that a digestibility below 50% can significantly reduce the voluntary dry matter intake of animals, with subsequent negative impacts on production performance. Except for Millettia ferruginea and Prosopis juliflora foliage, all assessed species had an IVOMD exceeding 50%, which makes them an ideal source for ruminant diets. The general trend of better digestibility in species with higher CP and lower fiber concentration is supported by the fact that forage digestibility has a strong positive correlation with protein value and a negative association with fiber concentration [72]. However, the correlation between digestibility and fiber content may depend on the structure and composition of the fiber fractions. Generally, species with high protein concentrations and low to moderate fiber fractions are likely to exhibit better digestibility values. Compared with the chemical composition and in vitro digestibility, which were found to vary widely between forage categories and forage species, the mean ME concentration was comparable. The determined mean ME value in the current analysis falls within the previously reported ME concentrations for the leaves and pods of indigenous browse species in Ethiopia [62,73]. However, the current values are lower than the values ranging between 10.42 and 12.31 MJ/kg DM reported for forage legumes studied by Berhanu et al. [70].

4.4. Tannin Content

The nutritive value of most indigenous browse species and forage legumes may not always be related to their chemical composition. This is because some species contain diverse plant secondary metabolites, such as tannins, alkaloids, saponins, and oxalates, which can limit nutrient utilization and reduce animal performance [27]. Tannins are complex phenolic compounds that are widely distributed in nutritionally valuable forage trees, shrubs, and legumes [74,75]. Table 5 shows the condensed tannin (CT) content of some common indigenous browse species and forage legumes in Ethiopia. Using their CT content, Acacia asak, Acacia seyal, Acacia tortilis Grewia bicolor, and Rhus natalensis can be categorized under tannin-rich browse species with elevated tannin values above 5% DM, which is commonly reported in the literature as a safe concentration for animal feeding [76]. A growing body of studies has recently supported that the presence of low to moderate concentrations of tannin have beneficial effects on ruminant nutrition and health [74,77]. The current literature shows that browse species, such as Balanites aegyptiaca, Cordia africana, Ficus thonningii, Millettia ferruginea, and Vernonia amygadalina, contain a low level of CT, whereas moderate concentrations of CT were determined in some indigenous browse species, including Dichrostachys cinerea, Albizia amara, Grewia tembesis, Prosopis juliflora, and Ziziphus spina-christi (Table 5).

Similar to browse species, some herbaceous forage legumes contain different types and concentrations of tannins. For example, birds-foot trefoil (Lotus corniculatus) and sainfoin (Onobrychis viciifolia) are well-known forage legumes adapted to temperate environments. They are good-quality forage legumes with moderate amounts of CT ranging from 10 to 40 g/kg and 30 to 80 g/kg, respectively, and it has been found that their CT has beneficial effects [78]. Similarly, Desmodium species (Desmodium intortum and Desmodium uncinatum) are tannin-rich herbaceous forage legumes that are mostly produced in tropical environments. They have high amounts of tannins with no or less adverse effects on their nutritive value when used for ruminant feeding [79]. Melesse et al. [46] reported 57.6 g/kg DM and 77.7 g/kg DM tannin phenol and total phenol, respectively, for Desmodium intortum, in addition to the extractable CT content of 77.6 g/kg DM. According to current findings, foliage of Cajanus cajan and tree lucerne also contains low levels of tannins from species reported from multipurpose fodder tree/shrub species.

Significant variations in extractable CT, tannin phenol, and total phenol content were observed between leaves and pods of different multipurpose fodder tree/shrub species [62]. Similar variations were reported for the morphological fractions of Sesbania sesban and Desmodium intortum in soluble tannin and CT contents by Debela et al. [80]. According to their report, leaves, twigs, whole forage, and green pods of Desmodium intortum contain soluble tannins of 207, 136, 173, and 100 g/kg DM, respectively. Thus, the tannin content of both browse species and forage legumes varied widely, associated with various factors. In addition to the plant species and variety effects, studies have reported the influence of growing environments, seasons, soil types, plant age, and the specific plant part analyzed on tannin concentrations in tannifeorus forage species [81]. The effects of seasons on the tannin accumulation of indigenous browse species have been investigated in Ethiopia, and the plant-species-dependent effects of seasons were reported in many studies [65,66,67,82]. In general, plant leaves tend to contain a high amount of tannins during the dry season. Seasonal effects on tannin accumulation could be partly linked to the soil moisture status and sunlight intensity. Tannins are one means of adaptation to environmental stress by plants. In line with this, Frutos et al. [77] reported an increase in tannin levels under high temperature, water stress, extreme light intensity, and poor-soil-quality conditions. It is assumed that most plant species have a tendency to contain higher tannin levels during the dry season than during the wet season. Moreover, the plants are penologically in their active growth during the wet season, and most of the available nutrients are primarily utilized for biomass accumulation. Consequently, the resources available or shared for tannin biosynthesis may be limited.

4.5. Nutrient Concentration of Experiment Diets and Feeding Patterns

The established database using animal experiments showed variations in various aspects of the experiment, including the amount of forage applied as a supplement, the amount of concentrate feed supplement being replaced by forage, type of forage legumes and browse species studied, and nutritional composition of the basal and supplementary diets. The determined mean supplementation level (277.5 ± 101.4 g/day) accounted for about 31.9 ± 11.4% of the total diet consumed by animals. This proportion is lower than the 42% reported in a previous meta-analysis on grass-based diets of goats in the tropics [25]. In the same study, it was predicted that the inclusion level of foliage should be between 50% and 60% of the total diet to achieve the maximum positive response to animal production performance. Similarly, Ali et al. [83] suggested supplementation levels exceeding 50% of the total diet for better feed intake and body weight gain in goats fed natural pasture grass hay substituted with leaves of indigenous browse plants. This indicates an available opportunity to increase the production responses of ruminants by further increasing the level of inclusion of the foliage supplement. However, this may require further supplementation-level studies involving the types of basal diets included. The important point is that, despite the presence of diverse genetic resources of browse species [9], with 148 species already being characterized for nutritional value in vitro (Table 1), only 29 species were assessed in animal experiments as potential sources of supplements in Ethiopia. Thus, the available potential is not fully explored to mitigate the prevailing feed quality gaps in the country.

The mean CP, NDF, ADF, and ADL concentrations of roughage feedstuffs used as basal diets in the included animal experiments in the database were consistent with the nutritional composition of hay produced from natural pastures and Rhodes grass in Ethiopia [10]. The reported CP content of basal diets is below the minimum recommended level (>7%) for optimal rumen microbial growth and activity in ruminant diets [48]. The fiber concentration of basal diets exceeds the amount (>55.0% NDF), which can significantly limit voluntary feed intake in ruminants [84]. In agreement with the current results, Castro-Montoya and Dickhoefer [24] reported that low-quality basal diets are used for ruminant feeding in tropical regions. In the current analysis, it was determined that basal diets were sourced from cultivated grass hay, natural pasture, and crop residues. Except for cultivated grass hay, the latter two are major feed sources for ruminants in Ethiopia [8,9]. Understanding the poor nutritional qualities of these major feed resources and for effective utilization in ruminal feeding, the major objectives of animal experiments were to balance their nutritional deficiency using nutrient-rich foliage of browse species and forage legumes and the substitution of high-cost concentrate supplements with the forage. The studied forage as a supplementary diet is supported by its superior nutritional value. The foliage had a comparable NDF but slightly lower CP content and higher ADF and ADL content than the concentrate feed mixes included as supplements. The CP content of the forage used for supplement surpassed that of the basal diet by 65.2%. In contrast, the foliage contained 41.9% less NDF and 38% less ADF than the control diet.

4.6. Nutrient Utilization and Production Performance

Two separate meta-analyses were performed to evaluate the effect of foliage of browse species and forage legume supplementation. The first analysis investigated the effects of forage supplementation using control treatment fed low-quality basal diets (natural pasture hay, crop residues and grass hay) ad libitum with no supplement (Table 7), whereas the second was to compare forage supplement with the concentration-based supplementation strategy (Table 8). The result demonstrated the positive impact of foliage of browse species and forage legume supplementation on the feed intake and apparent nutrient digestibility. The results revealed that DMI, CPI, NDFI, and MEI of the animals increased by 22.9%, 43.1%, 10.2%, and 31.4%, respectively, due to forage supplementation compared to the control group. However, the responses largely varied within the same dietary treatment, which could be further explained by multiple factors related to both basal and supplementary diet characteristics (Table A2). Similar to the current results, other studies reported that when the foliage of forage legumes and fodder trees are supplemented in the low-quality basal diets of ruminants, they can produce a significant improvement in the daily feed intake and digestibility of the diets [15,40]. The improvement in nutrient intake due to foliage inclusion could be attributed to changes in the chemical (nutrient composition) and physical characteristics of the total diet consumed by animals [85]. The studied foliage for supplementation purposes had superior nutritional value than the basal diets, and their inclusion can alter the nutritional composition of the total diet by increasing the protein content and diluting the fiber concentration in the diets [25,86]. Moreover, an increase in daily protein intake can result in an increase in DMI by enhancing the utilization of dietary fiber [87]. Hence, Tolera [15] discussed that the inclusion of forage legumes in ruminant diets as supplements can contribute to increased DMI and energy efficiency in animals fed low-quality roughages, such as crop residues. The nutritional value data summarized showed that browse plants and forage legumes are rich in protein (Table 3 and Table 4). The presence of their foliage at reasonable amounts in the diet can increase the amount of dietary nitrogen that can reach the rumen, which can support maximum rumen microbial growth and fiber degradation. The current finding is in agreement with the enhanced nutrient utilization efficiency and increased growth rate in goats fed low-quality tropical grass partially substituted with foliage of different browse species and forage legumes [25]. However, in contrast to the current finding, Castro-Montoya and Dickhoefer [24] reported that the inclusion of tropical legume silage in ruminant diets based on tropical grasses was associated with suppressive effects on protein intake and organic matter digestibility, although total DMI remained unaffected. Moreover, inconsistent responses in nutrient utilization between large and small ruminants have been observed when the grass portion of the diet was substituted with legume silage in a study focused on tropical forages. When the amount of foliage in the total diet consumed by animals increased, the intake of the basal diet was partly substituted by the supplement. These results are in agreement with the findings reported for different low-quality basal diets, such as maize stover supplemented with graded Desmodium intortum hay [88], urea-treated barely straw supplemented with Vicia species and Medicago sativa hay [89], and barely straw supplemented Tagasaste leaves [85]. Most of these authors indicated that the substitutional effects of supplements may not be desirable from both nutritional and economic perspectives. However, whether substitutional supplementation is desirable or not depends on the specific contexts of the production environment, particularly on the relative availability and cost of the basal or low-quality roughage and forage supplements and the production objective of the farm. This implies the importance of establishing an optimum inclusion level to enhance the intake and utilization of basal diets.

From the data analyzed on average daily gain (ADG), feed conversion efficiency (FCE), and carcass dressing percentage, ADG and FCE tended to respond with a similar trend to the nutrient utilization variables. Animals fed a forage-supplemented diet had a significantly higher ADG (p < 0.0001) than the control group (Table 8). The supplementation resulted in an increase in ADG by 70.1% compared to the control diet with no supplement (Table 6, 37.5 ± 4.8 g vs. 11.2 ± 5.1 g). Furthermore, the results of second analyses showed significant differences (p < 0.0035) among the different supplementation treatments in ADG, and the sole forage-supplemented group had lower weight gain performance than the sole concentrate supplement and concentrate partially substituted with forage treatments. The FCE-estimated-based ADG divided by daily DMI and empty body weight-based carcass dressing percentage showed a significant increase and improvement due to forage supplementation over the control treatment with no supplement (Table 7). Moreover, foliage supplementation had similar (p > 0.05) effects on carcass dressing percentage with sole concentrate and concentrate partially substituted by supplementary foliage treatments (Table 8). There was a great variation in the production responses reported between the studies included in the analysis. Several factors, including but not limited to animal characteristics (age, body weight, breed, etc.), feed characteristics (type of basal diet and forage, supplementation level, and mode of feeding), environment, and experimental settings, are the potential sources of variations [25]. The highest daily weight gain, FCE, and carcass yield recorded for forage-supplemented groups over the control could be due to increased nutrient density as a result of higher protein in the forage that reflected the increased total DM and nutrient intake. The current rate of increase in ADG (70.1%) due to foliage supplement was higher than the value reported (44.5% or increased from 26.6 g/d to 47.9 g/d) for goats fed tropical grass partly replaced by foliage [25]. In agreement with the current results, studies on the supplementation of crop-residue-based diets with herbaceous forage legumes in sheep diet [88], with leaves of multipurpose fodder trees [85] as well as foliage of indigenous browse plant supplementation to free-grazing goats during the dry period [90], increased the daily weight gain of the animals. On the other hand, despite similar FCE and carcass yield, the current findings showed that forage-supplemented animals had lower weight gain than their concentrate-supplemented counterparts. On the other hand, the level of partial substitution of concentrate feed with the study forage (47.6 ± 18.3%) did not produce any suppressive effects on the production rate. This is supported by a previous recommendation that the proportion of forage leaf meal used to replace the concentrate should not exceed 50% [91]. According to this study, despite the increased feed intake, which is similar to the current results, a replacement level above 50% resulted in decreased body weight gain and other carcass parameters in goats. In general, when the production objective is the attainment of a high level of productivity, the full replacement of concentrate feed by a forage supplement may require careful analysis and decisions by considering the economics of animal feeding.

5. Conclusions

The included studies in both databases were highly heterogeneous in the plant species and varieties studied, agroecology of forage sampling, nutrient concentrations, and digestibility. Despite these sources of variability, the nutritional values of different forage categories and species were summarized. Their results showed the extent to which different forage species, types, plant parts, harvesting stage, and conservation methods can vary in the nutritive values. From the overall results, forage from different categories have good nutritive values based on the determined high CP content (16.3 ± 3.6%–22.8 ± 3.2%), moderate fiber concentration (lower than 50% NDF, except twigs), moderate ME values (7.3 ± 1.0–8.9 ± 0.82 MJ/kg DM), and better digestibility level (IVOMD exceeding 50%). Accordingly, the in vivo result reveals the positive effects of these forages when included in low-quality basal diets as a supplement. It resulted in a significant improvement in nutrient intake, apparent digestibility of the nutrients, weight gain performance, and carcass yield of ruminants. This could provide an opportunity to fill the prevailing feed quality gaps in Ethiopia, particularly during the dry period. However, some species contain low to high levels of condensed tannins. The presence of tannins could have either detrimental or antinutritional effects or beneficial value in the nutrition and health status of the animals. The observed large variability in nutritional value could provide an opportunity to select browse species and forage legume varieties of superior nutritive quality. The determination of optimum inclusion levels by considering basal types may require careful consideration of local contexts and production objectives and may warrant future research focus.