Influence of Varying Dietary Kudzu Leaf Meal Particle Size on Performance, Breast Weight, and Organ Weight of Broiler Chickens from 1 to 21 Days of Age

Abstract

This research evaluated the influence of kudzu leaf meal particle size on body weight, feed consumption, feed conversion, breast weight, and organ weights of broilers. Treatments (4) included a control and kudzu leaf meal added to replace 2.5% soybean meal in a broiler starter diet at three particle sizes (1.00, 2.00, and 3.35 mm). Dietary treatments were fed to 240 male broilers over a 21 day grow out. Overall, there were no significant treatment effects for body weight, feed consumption, breast weight, or organ weights. There were no treatment effects for day 1 to 7 feed conversion (p > 0.05). There tended to be treatment differences for day 1 to 14 feed conversion (p = 0.052) and a significant effect between day 1 to 21 (p = 0.002). Feed conversion between day 1 to 21 was depressed at the 1.00 mm kudzu particle size. Based on this study, kudzu remains a viable protein source for inclusion in broiler diets and a particle size of 2 to 3 mm would be recommended.

1. Introduction

The poultry industry has rapidly grown due to efficiency of production and product affordability. This has resulted in increased production, placing a strain on accessibility of proteinaceous feed ingredients. Feed represents the highest cost in poultry production, with protein feedstuffs contributing the most to feed cost [1]. Traditionally, protein sources in poultry diets have been of either animal or plant origin, with plant-based protein sources costing substantially less. The most common protein source used in poultry diets is soybean meal. A number of other protein sources have been used in addition to or in replacement of soybean meal to enhance dietary amino acid profile or simply to reduce cost. Some examples include corn gluten meal, peanut meal, alfalfa meal, flaxseed meal, dried distillers’ grains, and animal-based sources (e.g., fishmeal, poultry meal, meat and bone meal). Larger poultry producers maintain high demand for these protein sources, leaving small-scale producers, particularly those in underdeveloped countries, with limited access to these ingredients. Smallholders have turned to a variety of plant leaf-based ingredients as protein substitutes. These leaf meals tend to be more accessible and often less costly than traditional protein ingredients. Further, leaf meals can play a phytogenic role in poultry nutrition. Leaf meals and other plant-based feed additives can play roles as antioxidants and antimicrobial agents, gut modulators, functional digestive aids, palatability enhancers, and potential growth promoters in poultry and other livestock species [2,3,4,5].

A potentially viable alternative proteinaceous feed ingredient is kudzu (Pueraria montana var. lobata) leaf meal (KLM). Kudzu is an invasive, semi-woody perennial vine native to Asia. It was originally introduced to the USA in the late 1800s for erosion control and soil improvements. By the 1970s, kudzu had been placed on the U.S. Department of Agriculture common weed list [6]. However, owing to its high level of digestibility, positive nutrient profile, and palatability, kudzu has been used to supplement grazing/browsing livestock species for decades [7]. Kudzu grows abundantly in tropical regions and holds promise as an affordable, alternative protein source in poultry feeds, particularly in regions with limited availability of proteinaceous feedstuffs, but an abundance of kudzu. The use of kudzu as a dietary supplement in poultry feeding has been limited and there is a paucity of research data on its viability as a poultry feed ingredient. In an early report, Polk and Gieger [8] successfully added kudzu to the diets of chicks at an inclusion rate of 9% in replacement of alfalfa leaf meal and found comparable bird performance responses. Gulizia and Downs [9] compared KLM to alfalfa meal added to a broiler starter diet and also showed similar performance responses between KLM and alfalfa meal. These investigators showed KLM to be a safe and viable alternative protein feedstuff in poultry diets.

Ingredient particle size in poultry diets can affect organ development, digestibility of nutrients, gut health, and enteric diseases [10]. Reducing particle size increases the surface area of feed ingredients, thereby increasing digestive enzyme interactions and enhancing growth efficiency. Additionally, reducing particle size in poultry diets can improve mixing characteristics and prevent nutrient segregation after mixing, creating more uniform ingredient distribution in finisher feeds. However, feed particle size excessively reduced is associated with increasing gastrointestinal passage rate, poor gut health, and low nutrient digestibility in broilers. Whole grains or coarsely ground ingredients reduce proventricular swelling and can influence gastrointestinal tract function, gizzard development, and reverse peristalsis. Finely ground feeds negatively impact gizzard development and reverse peristaltic contractions, which are critical for nutrient utilization and intestinal health [11]. Decreasing particle size lowers the grinding requirement of the gizzard, reducing its mass and limiting its function to a transit organ. Coarser particles rapidly enlarge the gizzard, enhancing digesta motility and backflow within the gastrointestinal tract.

Previous research has demonstrated KLM is a viable proteinaceous feedstuff in broiler diets [9]. This study continues previous kudzu research with the objective of assessing how varying particle sizes of kudzu leaf meal included in a broiler chicken starter diet impacts performance, breast weight, and organ weights from 1 to 21 days of age. This research will further seek to elicit a recommended KLM particle size for inclusion in poultry diets.

2. Materials and Methods

2.1. Kudzu Collection and Preparation

Kudzu used in this research was collected from six different counties in the middle Tennessee area (Bedford, Cannon, Coffee, Dekalb, Moore, and Rutherford). Sample collection occurred during June, peak kudzu growing season in the southern USA. A 30.5 cm² polyvinyl chloride (PVC) square was randomly tossed into clusters of free growing kudzu. Content within the square was collected by clipping 15 cm depth of kudzu vine. After collection, leaves were removed and dried at 60 °C for 48 h. After drying, all kudzu leaf samples were equally compiled into one composite sample across all counties. Dried kudzu leaves were ground to pass through either a 1.00, 2.00, or 3.35 mm sieve (USA Standard Testing Sieve, Soiltest, Inc., Lake Bluff, IL, USA) to create three KLM particle sizes for dietary incorporation. Sieves were stacked on an electronic shaker (Octagon 200 Test Sieve Shaker, Endecotts, Newtown, PA, USA) to separate and compile the three kudzu particle sizes. Nutrient analysis of KLM used in this study is shown in

Table 1. Analyzed nutrient composition of kudzu leaf meal incorporated into experimental diets (as fed basis).

Analysis A	Kudzu Leaf Meal
Dry matter, %	88.5
Crude protein, %	25.5
Available Protein, %	23.5
Acid detergent fiber, %	19.4
Neutral detergent fiber, %	29.6
Lignin, %	4.7
Metabolizable energy, kcal/kg	2680
Calcium, %	1.70
Phosphorus, %	0.30
Magnesium, %	0.16
Potassium, %	1.49
Sulfur, %	0.36
Chlorine, %	0.27
Lysine, %	1.19
Methionine, %	0.38

^A Conducted using near-infrared reflectance spectroscopy (NIRS) [12,13]; Foss NIR Systems Models XDS and 6500 with ISIScan v.4.6.12, Eden Prairie, MN, USA.

.

2.2. Diet Preparation

Kudzu leaf meal was incorporated into a basal broiler starter diet (mash form) at one of the three KLM particle sizes to create three experimental diets (

Table 2. Ingredient and nutrient compositions of experimental diets (as fed basis).

Ingredient, % of Diet	Control	KLM1 A	KLM2 A	KLM3 A
Corn	49.38	49.38	49.38	49.38
Soybean meal, 46% crude protein	38.37	35.87	35.87	35.87
Corn oil	4.11	4.11	4.11	4.11
Distillers dried grains with solubles	4.00	4.00	4.00	4.00
Dicalcium phosphate	1.63	1.63	1.63	1.63
Ground limestone	1.36	1.36	1.36	1.36
Salt (NaCl)	0.38	0.38	0.38	0.38
DL-methionine	0.33	0.33	0.33	0.33
L-lysine	0.17	0.17	0.17	0.17
Trace mineral premix B	0.10	0.10	0.10	0.10
Vitamin premix C	0.10	0.10	0.10	0.10
Choline chloride	0.07	0.07	0.07	0.07
Kudzu leaf meal	0.00	2.50	2.50	2.50
Total	100.0	100.0	100.0	100.0
Calculated nutrient analysis, % (unless otherwise noted)
Dry matter D	90.0	89.0	89.5	90.8
Crude protein D	23.1	21.9	22.0	22.2
Metabolizable energy, kcal/kg	3000	3000	3000	3000
Acid detergent fiber D	4.9	4.5	4.8	5.2
Neutral detergent fiber D	8.6	9.4	9.8	9.4
Calcium	1.00	− E	− E	− E
Available phosphorus	0.40	−	−	−
Sodium	0.18	−	−	−
Potassium	1.01	−	−	−
Chlorine	0.30	−	−	−
Digestible lysine	1.23	−	−	−
Digestible methionine	0.64	−	−	−
Digestible threonine	0.73	−	−	−
Digestible tryptophan	0.25	−	−	−

^A Kudzu leaf meal (KLM) particle size; KLM ground to pass 1.00 (KLM1), 2.00 (KLM2), or 3.35 (KLM3) mm sieve. ^B Trace mineral premix included per kg of diet: Mn (manganese sulfate), 120 mg; Zn (zinc sulfate), 100 mg; Fe (iron sulfate monohydrate), 30 mg; Cu (tri-basic copper chloride), 8 mg; I (ethylenediamine dihydroiodide), 1.4 mg; and Se (sodium selenite), 0.3 mg. ^C Vitamin premix included per kg of diet: Vitamin A (Vitamin A acetate), 18,739 IU; Vitamin D (cholecalciferol), 6614 IU; Vitamin E (DL-alpha tocopherol acetate), 66 IU; menadione (menadione sodium bisulfate complex), 4 mg; Vitamin B12 (cyanocobalamin), 0.03 mg; folacin (folic acid), 2.6 mg; D-pantothenic acid (calcium pantothenate), 31 mg; riboflavin (riboflavin), 22 mg; niacin (niacinamide), 88 mg; thiamine (thiamine mononitrate), 5.5 mg; D-biotin (biotin), 0.18 mg; and pyridoxine (pyridoxine hydrochloride), 7.7 mg. ^D Analyzed values. ^E Values not available for KLM.

). Kudzu leaf meal was added into the basal diet at a rate of 2.5% soybean meal replacement. The basal diet represented a typical broiler starter diet and was used as the control in this experiment. All diets were prepared at the Auburn University Animal Nutrition Center. Feed was manufactured approximately 7 ± 1 d prior to the starter phase. Whole corn was ground with a hammermill (Model 11.5 × 38, Roskamp Champion, Waterloo, IA, USA) equipped with a 4.76 mm screen. Feed ingredients were blended for 150 s (30 s dry cycle and 120 s wet cycle) using a twin shaft mixer (Model 726, Scott Equipment Co., New Prague, MN, USA) to produce the mash diets. After mixing, KLM at each particle size and the basal diet was mixed for 5 min in a Marion Mixer (Model 2010, Rapids Machinery Company, Marion, IA, USA) to manufacture each treatment with KLM inclusion. During feed manufacture, feed samples were collected at evenly spaced intervals for nutrient analysis. The starter feed used in each treatment met or exceeded National Research Council (NRC) requirements [14] and Cobb 500 nutrient recommendations [15].

2.3. Nutritional Analysis

Samples of KLM and complete dietary treatments were obtained and submitted for nutrient analysis at a commercial laboratory (Dairy One Laboratory, Ithaca, NY, USA). Kudzu leaf meal samples were analyzed using NIRS protocols [12,13] (Table 1). Complete diets were analyzed for dry matter (DM) [16], crude protein (CP) [17], neutral detergent fiber [18], and acid detergent fiber [18].

2.4. Bird Management and Data Collection

Animal handling procedures were approved by the Middle Tennessee State University Institutional Animal Care and Use Committee (IACUC) under proposal 21-2001 and conformed to accepted practices [19,20]. Day-old Cobb 500 byproduct males (240) were obtained from a local complex and randomly assigned to 16 battery cages (15 birds per cage; 527 cm²/bird) and treatments randomly assigned to each cage (4 treatments; 4 replicate cages/treatment; 60 birds/treatment). Birds were brooded at 35 °C and reduced 3 °C every 7 days. Room temperature was maintained at 27 °C. Continuous light was provided (24 L:0 D; 25 lux) with feed and water offered ad libitum. Feeder (9.6 cm/bird) and drinker (4.8 cm/bird) space met or exceeded that recommended for broilers grown to 21 days of age [19,20].

All birds were weighed at day 1, 7, 14, and 21 to determine average body weight and weight gain. Feed consumption was determined using feed offered and feed remaining on designated days bird weights were determined. Feed conversion (FCR) was calculated using feed consumption and body weight gain data and was adjusted for mortality. On day 21, 5 birds per pen were randomly selected and humanely euthanized according to AVMA guidelines [21] to assess breast and select organ weights. Whole carcasses were water emersion chilled at 1 °C for 10 h. After chilling, whole breast was removed by cutting through ribs and at the junction of the coracoid, scapula, and clavicle and then weighed. Gizzards were removed at the proventricular-ventricular junction and the gizzard-duodenal loop junction, opened, koilin lining removed, and rinsed free of digesta prior to weighing. Ceca were excised at the ileo-colonic-cecal junction. The entire small intestine (with pancreas) was removed at the ileo-colonic-cecal junction and gizzard-duodenal loop junction. Organ weights were assessed as absolute (g/bird) and as percent of body weight.

2.5. Statistical Analysis

Data were analyzed as a completely randomized design with battery cage representing the experimental unit and each treatment represented by 4 replicate cages. Mortality data were subjected to arcsine transformation before statistical analysis. Data were analyzed as a one-way ANOVA using the general linear model (GLM) procedure of the SAS statistical package [22] with the following model:

Y_ij = µ… + τ_i + β_j + ε_ij

where Y_ij is the observed response of broilers in each pen; µ… is the overall mean; τ_i is the fixed effect of KLM inclusion such that ∑τ_i = 0; β_j are identical and independently normally distributed random effects with mean 0 and variance σ²β such that ∑β_j = 0; and ε_ij are identical and independent random errors that follow a normal distribution with mean 0 and variance σ². Least square means among the 4 treatments were compared using post hoc Tukey’s HSD procedure, and all data were analyzed for normality using the Shapiro–Wilk test. Statistical significance was established at p ≤ 0.05. Statistical tendency was considered as 0.05 < p < 0.10. Independent orthogonal contrasts were performed for KLM grouped comparison to control.

3. Results

Live performance data are presented in

Table 3. Live performance influence from varying kudzu leaf meal (KLM) particle size added to a broiler starter diet fed day 1 to 21.

Item	Control	KLM1 A	KLM2 A	KLM3 A	Pr > F	SEM
Average body weight, g/bird
Day 1	43.1	42.1	42.8	43.1	0.553	0.57
Day 7	142	134	139	137	0.673	5
Day 14	391	361	374	365	0.472	13.7
Day 21	882	785	786	795	0.204	25.5
Body weight gain, g/bird
Day 1 to 7	99.4	91.8	96.3	94.2	0.733	4.91
Day 1 to 14	348	319	331	322	0.486	13.7
Day 1 to 21	839	743	743	752	0.205	25.4
Feed consumption, g/bird
Day 1 to 7	124	113	112	116	0.598	6.8
Day 1 to 14	562	556	536	525	0.489	18.3
Day 1 to 21	1157	1114	1085	1081	0.245	27.9
Feed conversion B, g:g
Day 1 to 7	0.87	0.84	0.8	0.84	0.439	0.032
Day 1 to 14	1.43	1.53	1.43	1.44	0.052	0.027
Day 1 to 21	1.32 b	1.42 a	1.38 a,b	1.36 b	0.002	0.014

^A Kudzu leaf meal (KLM) particle size; KLM ground to pass 1.00 (KLM1), 2.00 (KLM2), or 3.35 (KLM3) mm sieve. ^B Adjusted for mortality. ^a,b Means in the same row with different superscripts are significantly different (p < 0.05).

. Breast and organ weight data are presented in

Table 4. Breast and organ parameter influence from varying kudzu leaf meal (KLM) particle size added to a broiler starter diet fed day 1 to 21.

Item	Control	KLM1 A	KLM2 A	KLM3 A	Pr > F	SEM
Whole breast wt., g/bird B	187	184	173	178	0.370	6.0
Gizzard wt., g/bird C	23.9 a	21.1 b	21.0 b	22.6 a,b	0.005	0.51
Gizzard wt., % D	2.7	2.7	2.7	2.8	0.543	0.08
Ceca wt., g/bird C	10.3	11.8	10.1	9.7	0.399	0.89
Ceca wt., % D	1.2	1.5	1.3	1.2	0.277	0.001
Small intestines wt., g/bird C,E	58.3	57.6	55.8	58.1	0.894	2.59
Small intestines wt., % D	6.6	7.3	7.2	7.3	0.528	0.004

^A Kudzu leaf meal (KLM) particle size; KLM ground to pass 1.00 (KLM1), 2.00 (KLM2), or 3.35 (KLM3) mm sieve. ^B Whole breast = skinless, bone-in Pectoralis major and minor. ^C Average weight per chilled carcass. ^D Percent of chilled whole bird. ^E Small intestines harvested with pancreas. ^a,b Means in the same row with different superscripts are significantly different (p < 0.05).

.

Table 5. Results of an independent orthogonal contrast analysis comparing control to grouped KLM treatment means (KLM1 + KLM2 + KLM3).

Control vs. Grouped KLM Treatments
Item	Higher Value A	Difference	p-Value	Pooled SEM
Average body weight, g/bird
Day 1	Control	0.4	0.532	0.66
Day 7	Control	5	0.336	5.8
Day 14	Control	24	0.161	15.9
Day 21	Control	93	0.042	30.8
Body weight gain, g/bird
Day 1 to 7	Control	5.3	0.365	5.67
Day 1 to 14	Control	24	0.166	15.8
Day 1 to 21	Control	93	0.042	30.8
Feed consumption, g/bird
Day 1 to 7	Control	10	0.21	7.9
Day 1 to 14	Control	23	0.312	21.2
Day 1 to 21	Control	64	0.072	32.2
Feed conversion, g:g
Day 1 to 7	Control	0.04	0.227	0.037
Day 1 to 14	KLM	0.04	0.25	0.032
Day 1 to 21	KLM	0.07	0.002	0.016
Whole breast weight, g/bird	Control	9	0.222	34.7
Gizzard weight, g/bird	Control	2.3	0.002	2.96
Gizzard weight, %	KLM	0.03	0.772	0.004
Ceca weight, g/bird	KLM	0.2	0.81	5.16
Ceca weight, %	KLM	0.13	0.255	0.007
Small intestines weight, g/bird	Control	1.1	0.698	14.98
Small intestines weight, %	KLM	0.67	0.164	0.022

^A Italicized text represents a statistical difference between control and grouped KLM means for the variable.

presents data from an independent orthogonal contrast analysis comparing the control treatment with the grouped means of KLM treatments (KLM1 + KLM2 + KLM3).

3.1. Body Weight

There were no significant differences between the control and KLM diets and among KLM particle sizes (p > 0.05) for average body weight at day 1, 7, 14, and 21. Likewise, KLM particle size did not influence body weight gain between day 1 to 7, 1 to 14, or 1 to 21 (p > 0.05) (Table 3). Interestingly, when KLM treatments were grouped and compared to control, a significant effect on day 21 BW and day 1 to 21 BWG were elucidated. Grouped KLM treatments had a 10 and 11% respective lower day 21 BW and day 1 to 21 BWG (Table 5).

3.2. Feed Consumption

There were no kudzu particle size treatment differences for feed consumption among control, 1.00, 2.00, and 3.35 mm particle size during day 1 to 7, 1 to 14, and 1 to 21 (p > 0.05) (Table 3). Kudzu leaf meal treatments, when grouped, did tend to depress day 1 to 21 feed consumption when compared to control (Table 5).

3.3. Feed Conversion Ratio

There were no kudzu particle size treatment effects for feed conversion ratio between day 1 and 7. However, day 1 to 14 FCR tended to differ among treatments (p = 0.052) (Table 3). More pronounced treatment differences in FCR were observed for day 1 to 21, with kudzu addition at 1.00 mm depressing FCR compared with control. Incorporation of larger kudzu particle sizes (2.00 and 3.35 mm) resulted in similar FCR to birds fed the control diet (Table 3). Overall, KLM treatments, when grouped, and compared to control resulted in a 6-point FCR increase (Table 5).

3.4. Mortality

Mortality was monitored throughout the entire study (day 1 to 21). There were no statistical differences observed between treatments (p > 0.05; control = 8.3%; KLM1 = 6.7%; KLM2 = 5.0%; KLM3 = 5.0%).

3.5. Breast and Organ Parameters

There were no significant particle size treatment effects for breast, ceca, and small intestine data (p > 0.05). Absolute gizzard weights (g/bird) were highest for birds receiving the control diet compared to 1.00 and 2.00 mm particle size. The largest KLM particle size treatment did not produce gizzard weights that differed from control or the smaller KLM particle size treatments (Table 4). Higher gizzard weights (almost 10%) for birds on the control treatment when compared to grouped KLM treatments were likely a result of higher BW for control birds (Table 5). Observed differences for absolute gizzard weight disappeared when relative gizzard weights were compared across treatments.

4. Discussion

As stated previously, there are limited data on the addition of KLM to poultry diets. In the present study, KLM inclusion (2.5%) at all particle sizes did not depress body weight of birds compared to the control, with the control treatment being comparable to a typical U.S. broiler industry diet. Increasing levels of KLM, however, beyond the inclusion rate in the present study, would likely produce negative body weight effects. This is consistent with another report showing an inverse relationship between dietary tropical kudzu (Pueraria phaseoloides) level in a broiler diet and weight gain [23]. In fact, these investigators concluded that tropical kudzu leaf meal should not be included in broiler diets. Leaf meals included in broiler diets at high inclusion rates can negatively affect growth performance through a dilution effect on dietary nutrient concentrations, thus leading to decreased nutrient availability and metabolizable energy concentration [24]. Further, there is the likelihood of anti-nutritional factors (e.g., tannins, non-starch polysaccharides) in kudzu and other leaf meals playing some role in broiler growth depression. This, however, has not been completely fleshed out in poultry. Gulizia and Downs [9] found that broilers fed a diet containing kudzu leaf meal (6% inclusion rate) exhibited an 8.5% lower average body weight compared to birds on a typical corn-soybean meal diet without KLM. Based on these results and others, it appears clear that KLM inclusion rates in broiler diet above 5% can negatively influence growth performance. Further investigation is needed to flesh out an ideal KLM inclusion level to optimize bird performance.

Some studies have demonstrated that leaf meals decrease body weight gain by depressing feed consumption. Despite this, Etela et al. [25] demonstrated that a commercial broiler diet supplemented with tropical kudzu did not affect total feed intake and total body weight gain. Gulizia and Downs [9] determined that kudzu leaf meal at a 6% inclusion rate reduced feed consumption by 5%. Another study evaluated Acacia angustissima leaf meal as a protein substitute in broiler diets and demonstrated a negative linear response on feed intake and body weight gain as dietary levels increased [24].

It is hypothesized that the feed conversion effects in the present study resulted from birds sorting through the larger kudzu particles and consuming more of the basal diet. This was anecdotally observed but not measured. Likely birds on the 1.00 mm KLM particle size diet could not efficiently sort kudzu particles, and were therefore, actually consuming more KLM. There may also be a fiber bulk effect influencing broiler growth. The KLM used in this study contained a considerable concentration of neutral detergent fiber (NDF) (Table 1). In the chicken, higher fiber diets tend to decrease feed digestibility, increase impaction of the gastrointestinal tract, and dilute nutrients, leading to a decrease in available nutrients and dietary metabolizable energy concentration [26,27,28]. As such, increased dietary fiber content negatively impacts broiler performance. After day 7 in the present study, birds on KLM treatments may have experienced a fiber bulkiness effect, thus contributing to their depressed feed conversion compared to birds on the control diet, particularly with the smaller particle size KLM.

Kudzu’s supplementation resulting in no influence on bird mortality is consistent with prior research [8,9] demonstrating kudzu inclusion in poultry diets to be a safe alternative protein source.

Gulizia and Downs [9] demonstrated that inclusion of KLM depressed breast weight compared to birds consuming a control diet. They also demonstrated increased gizzard weights in birds consuming a KLM supplemented diet. This is somewhat inconsistent with the results from the present study which showed absolute gizzard weight was lower by approximately 12% in birds consuming 1.00 and 2.00 mm KLM compared to birds consuming the control diet. This same effect was not seen in birds on the 3.35 mm treatment. Likely particle sizes were not large enough to illicit a gizzard hypertrophic effect. Other research has shown gizzard size increases when diets contain significant structural plant components [29,30]. Elevated dietary fiber also increases gizzard volume and ability to retain digesta for longer periods of time causing a pH change in the gizzard environment [31]. Although higher than control in the present study, fiber content did not appear high enough with KLM replacement to influence the gizzard.

Although there were no statistical differences among treatments for body weight and body weight gain, it is worth noting that numerical values for the 3.35 mm KLM particle size diet yielded the most similar results to the control diet. As stated previously, this is likely from birds sorting through the larger kudzu particle sizes and mainly consuming the basal diet (into which KLM was mixed). Birds on the 1.00 mm KLM particle size diet did not perform as well compared to birds on the control, 2.00, and 3.35 mm diets. Birds on the 1.00 mm treatment were likely prevented from sorting added kudzu effectively, thus consuming significantly more fiber and experiencing some bulkiness effect. Although some performance losses were noted with KLM supplementation, particularly with smaller particle size inclusion, birds consuming KLM at all particle sizes still performed at a relatively high level and are comparable to industry broiler performance standards [15].

5. Conclusions

Overall, KLM added in replacement of some soybean meal in a broiler starter diet did not substantially depress most bird performance parameters, breast weight, or organ weights compared to control. Results from this study indicate that diets containing KLM particle size of approximately 2.00 mm would be recommended to prevent excessive fiber consumption or sorting while avoiding performance losses associated with smaller particle sizes. Further research should focus on higher KLM/SBM replacement rates and potential treatment effects during a longer growing period as well as crumbled and pelleted diets to reduce feed sorting. While use of traditional protein sources does result in more optimum bird performance, kudzu appears to be a viable protein supplement option, particularly in regions with limited access to more traditional proteinaceous feed ingredients.