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Article

Sustainable Use of Pennisetum sinese: Effect on Nutritional Components and Fermentation Quality of Stylosanthes guianensis in Tropics

by
Yuanting Yang
,
Qun Wu
,
Hu Liu
,
Ke Wang
,
Meng Zeng
,
Xiaotao Han
,
Weishi Peng
,
Hanlin Zhou
* and
Jiancheng Han
*
Zhanjiang Experimental Station, Chinese Academy of Tropical Agricultural Sciences, Zhanjiang 524013, China
*
Authors to whom correspondence should be addressed.
Sustainability 2023, 15(16), 12484; https://doi.org/10.3390/su151612484
Submission received: 20 July 2023 / Revised: 10 August 2023 / Accepted: 15 August 2023 / Published: 17 August 2023
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Abstract

:
Mixed ensiling of Stylosanthes guianensis and Pennisetum sinese is an alternative method to improve the nutrient composition of feeds for healthy and green ruminant production in the tropics. This study examined the fermentation quality, nutritional composition, and microbial population in silage to select the most suitable ratio of mixed silage containing different proportions of S. guianensis and P. sinese. It was completely randomized and consisted of four treatments with five replications based on fresh weight as follows: S0, 100% P. sinese; S15, 85% P. sinese + 15% S. guianensis; S30, 70% P. sinese + 30% S. guianensis; and S45, 55% P. sinese + 45% S. guianensis. The silage samples were opened and detected after ensiling for 30 days. The results showed that the content of dry matter and crude protein in mixed silage increased with the increase in S. guianensis, while the content of acid detergent fiber decreased significantly, and the maximum or minimum value appeared in the S45 group. As the proportion of S. guianensis increased, the pH, ammonia nitrogen, and acetic acid in mixed silage gradually increased, but the lactic acid content decreased. In addition, the content of lactic acid bacteria and yeast showed a significant downward trend. Further study showed that there was a complex correlation between nutrient compositions, fermentation characteristics, and microbial numbers in mixed silage, especially dry matter, crude protein, and lactic acid bacteria. From the sensory evaluation of silage, S30 was excellent and exhibited an aromatic smell, a hazel color, and the loosest texture. However, from the results of the proportion of organic acids in mixed silage fermentation and further principal component analysis, the highest comprehensive score was in the S15 group. Considering the nutritional compositions and fermentation quality, the optimum ratio of mixed fermentation between S. guianensis and P. sinese in this experiment was 30:70.

1. Introduction

Forages are an important source of feed for livestock around the world, especially for the millions of smallholder farmers who depend on pastures and rangelands as the foundation of sustainable livestock systems [1,2]. Ruminants can digest, absorb, and convert them into food, providing humans with high-quality milk and meat products to safeguard the basic nutrients needed for human growth, health, and cognitive development [3,4]. Moreover, forages play an important role in natural resource management and carbon sequestration to reduce soil erosion and mitigate the effects of climate change, particularly for the available meager land or tropical regions [5,6]. Pennisetum sinese is a versatile, strong-adaptability and high biomass-production-rate gramineous forage, mainly distributed in tropical or subtropical regions around the world [7,8]. Because of its fast growth rate, high lignocellulosic biomass, and good palatability, it is widely used as a feedstock for ruminants and biofuels [7,9,10]. P. sinese grows rapidly and produces excess forage grass during the rainy season in summer, but it grows slowly or even stops growing in winter, which easily causes a seasonal shortage of green feed. This phenomenon has seriously affected the healthy and sustainable development of livestock husbandry in the tropics [8]. To combat this and meet sustainable demand throughout the year, P. sinese needs proper pretreatment and protection. Using ensiling as a means of curbing the supply problem is an efficient idea since feedstocks can be preserved for long periods and provide a potential platform for pretreatment [11,12]. Besides maintaining feed quality for long-term storage, ensiling also exhibits promise as a pretreatment method for biofuel production [13,14]. However, due to its high content of water and lignin cellulose, P. sinese is extremely susceptible to mildew and decay, leading to silage failure, especially under tropical conditions of high temperature and humidity [8,14,15]. Although numerous studies have shown that silage additives, including chemicals, enzymes, lactobacillus and non-lactobacillus, can improve the quality of silage fermentation by improving lactic acid fermentation, inhibiting spoilage microorganisms, or enhancing aerobic stability and reducing nutrient degradation [16,17,18,19], only gramineous forage silage, such as P. sinese, has a high fiber content, low digestibility and protein content, and a predominance of undesirable bacteria, which cannot meet the nutritional requirements of high-yielding ruminants; this also greatly limits its application in ruminant feed production [8,20,21].
Mixed silage has the advantages of balanced forage nutrition, reduced content of harmful substances in the silage, and improved fermentation quality and digestibility of forage grass [21,22]. In addition, mixed silage of forages can not only solve the difficulty of successful sole silage, but also compensate for the nutrient imbalance caused by single silage, which can increase the content of crude protein and the quality of silage in mixed silage [23]. Previous studies have shown that adding legumes to forage silage can improve the fermentation quality and optimize the microbial community structure, which is a feasible strategy to improve the utilization rate of forage and meet sustainable utilization throughout the year [21]. Stylosanthes guianensis is one of the most adaptable, productive, and quickly growing tropical forage legumes, and it is also widely used in livestock production in many places with tropical or subtropical climates [24,25]. S. guianensis has good feeding nutritional value, such as high crude protein (15–20%), dry matter (15–25%) and good palatability, which can be used as a substitute for reducing protein concentrate in beef cattle breeding diet in tropical conditions [24,26,27]. It was reported that 600 g/kg S. guianensis silage supplemented in beef concentrate had similar performance to the same corn silage [28]. Furthermore, a study on the effect of different proportion of S. guianensis on mixed silage of palisade grass showed that the high proportions of S. guianensis on mixed silage had better nutritional value and fermentation quality [29].
Given this, we speculate that adding an appropriate amount of S. guianensis to P. sinese silage is a feasible strategy to improve the success rate of fermentation and provide fresh roughage for animals continuously. However, to our knowledge, the appropriate ratio of the mixed silage of P. sinese and S. guianensis is not clear, and the relationship between the nutritional composition, microbial quantity and fermentation quality of the mixed silage is still limited. Therefore, the present study was performed to identify the optimum proportion and interrelation by evaluating the quality, nutrition, and microbial population of silage with different ratios of S. guianensis and P. sinese. The results will be beneficial for the development and utilization of resources of high-quality forage grass and solve the problem of year-round roughage supply.

2. Materials and Methods

2.1. Silage Preparation

S. guianensis and P. sinese were selected from the Zhanjiang Experimental Station of the Chinese Academy of Tropical Agricultural Sciences (21°02′ N, 110°12′ E, Guangdong, China). S.guianensis was in its first flowering period, with dry matter (DM) content of 34.02% of fresh weight (FM). In addition, the contents of crude protein (CP), crude fat (CF), neutral detergent fiber (NDF), and acid detergent fiber (ADF) based on DM were 15.61%, 2.86%, 44.51%, and 29.23%, respectively. P. sinese was mowed at a height of 2–2.5 m, with DM content of 19.62% of FM. And the CP, CF, NDF, and ANF based on DM were 11.80%, 2.06%, 59.67%, and 15.60%. After harvesting and slicing into 2–3 cm pieces, S. guianensis and P. sinese were sampled individually, and mixed at ratios of 0:100, 15:85, 30:70 and 45:55 on an FW basis, thereby resulting in corresponding treatments of S0 (control), S15, S30 and S45, respectively. For each of five replicates per treatment, the mixed sample was packed into a plastic film bag, vacuumed by a sealer and stored at room temperature for 30 days.

2.2. Sample Processing and Analysis

The silage sample plastic bags were opened, and the upper and lower 10 cm of silage samples were removed. The rest of the samples were mixed by the quartering method and collected to analyze the nutritional compositions and fermentation quality.

2.2.1. Nutritional Composition and Microbial Population

The DM of fresh ensiling material or silage was determined by drying at 65 °C for 72 h to a constant weight a, then ground through a 1 mm sieve by a laboratory knife mill, and stored in a desiccator sieve for chemical analysis. The total nitrogen (TN) of fresh ensiling material or silages was determined by the standard macro Kjeldahl method [30], and CP was calculated as TN × 6.25. The NDF and ADF contents of fiber were determined using the Van Soest detergent filter method [31]. The concentration of water-soluble carbohydrate (WSC) was analyzed by colorimetry after reaction with anthrone reagent according to Murphy [32].
For the determination of counts of microorganisms, 10 g of fresh silage was tenfold serially diluted by 0.85% sodium chloride [33]. The population of the lactic acid bacteria (LAB) and the yeast were cultured in the MRS Agar medium and potato glucose agar medium, respectively. LAB was cultured in an anaerobic incubator at 37 °C for 3 days. The yeast was cultured in a biochemical incubator at 25 °C for 3 days.

2.2.2. Fermentation Characteristics

The silage was weighed to 20 g and put into a 250 mL-wide triangular bottle. Next, 180 g of deionized water was added to the bottle. The extract was obtained at 4 °C for 24 h and then filtered through four layers of gauze and qualitative filter paper. One part of the extracted juice was used to detect the pH by using the FE320pH meter [Mettler-Toledo apparatus (Shanghai) Co., Ltd.]. The rest of the extracted juice was stored at −20 °C for the analysis of the organic acid [lactic acid (LA), acetic acid (AA), propionic acid (PA), butyric acid (BA)], and ammonia nitrogen (NH3-N). The NH3-N content was determined by the phenol-sodium hypochlorite colorimetry method according to Broderick and Kang [34]. In addition, LA, AA, PA, and BA contents were determined by a high-performance liquid chromatograph (Shimadzu-LC 20A) [35]. The test conditions were determined by using a chromatographic column for Agilent5TC-C18 250 × 4.6 mm and a UV detector. The detection wavelength was 210 nm, the mobile phase was 3 mmol/L perchloric acid solution, the flow rate was 0.8 mL/min, and the column temperature was 30 °C.

2.2.3. Silage Sensory Evaluation

According to the silage sensory evaluation of the German Agricultural Association (Deutsche Landwirtschafts Gesellschaft), the silage color, smell, and texture, which were used to analyze and evaluate the sensory quality, could be divided into four grades (with a maximum of 20 points) as follows: excellent, 16–20; good, 10–15; medium, 5–9; and corrupt, 0–4. In this experiment, the sensory evaluation of silage was discussed in groups, and the silage quality index and silage quality index were discussed by five trained experts.

2.3. Statistical Analysis

The data of the fermentation characteristics were analyzed using ANOVA (IBM SPSS 20.0). Significant differences in the results of each group were analyzed and compared by Duncan’s method. The significant effects of different treatments were analyzed using the significant difference in Duncan’s test, with the significance set to p < 0.05. After log transformation, principal component analysis (PCA) was also performed in SPSS 20.0 software. Correlation analysis and a graph drawing were performed using Origin 2021 software (Northampton, MA, USA).

3. Results

3.1. Nutritional Compositions of Silage

The nutritional compositions of the silage are shown in Table 1. The different levels of S. guianensis significantly increased the DM and CP contents of the silage, with S45 showing the highest value (p < 0.05). Moreover, the contents of CP in S15–S45 were significantly higher than that in S0 (p < 0.05). The ADF content of silage linearly decreased in response to the increase in the level of S. guianensis (p < 0.05), whereas the WSC and NDF contents were not significantly different between the groups (p > 0.05).

3.2. Fermentation Characteristics of Silage

Table 2 shows that as the proportion of S. guianensis increased, the pH, NN3-N and AA values gradually increased, with S45 showing the highest value (p < 0.05). Compared with the S0, the pH and AA of silage in S45 significantly increased, but there was no significant difference between S15 and S30 (p > 0.05). Although the NN3-N concentration decreased gradually with the increase in the proportion of S. guianensis (p < 0.05), there was no significant difference between S15 and S30 groups. Compared with S0, the LA of the other groups showed a decreasing trend but without a significant difference between treatments (p > 0.05). Moreover, the ratio of LA/AA in S0 and S15 was significantly higher than in S30 and S45 (p < 0.05). Compared with S0, the PA content in each treatment group decreased significantly (p < 0.05). In addition, BA was detected in all test groups, and S45 had the lowest BA content compared with other treatments.

3.3. The Lactic Acid Bacteria and Yeast Population of Silage

The LAB bacteria and yeast populations decreased gradually together with the increase in the proportion of S. guianensis (Figure 1). Although the LAB of silage in S15–S45 groups were significantly lower than that in S0 (p < 0.05), the numbers of LAB were all greater than 1 × 104 CFU/g FM. From the fitting curve, the decline rate of LAB from S15 to S45 is slower than that from S0 to S15. Similarly, compared with S0, the yeast content in each treatment group decreased significantly (p < 0.05), but the decline rate of yeast from S30 to S45 was higher than from S0 to S30.

3.4. Correlation Analysis of Silage

The correlation analysis of nutritional compositions, fermentation characteristics and microbial quantity is shown in Figure 2. In terms of nutritional compositions, DM, CP and WSC were significantly positively correlated with each other (p < 0.05), and were significantly negatively correlated with NDF and ADF (p < 0.05). However, NDF is positively correlated with ADF (p < 0.05). For fermentation characteristics, the pH of silage was significantly positively correlated with NH3-N, LA and AA (p < 0.05). In addition, NH3-N was positively correlated with AA, but negatively correlated with PA (p < 0.05). The number of LAB in silage was negatively correlated with yeast but without a significant difference (p > 0.05). The nutritional compositions, fermentation characteristics and microbial quantity of silage were also closely related, in which there was a significant positive correlation among DM, CP, pH and LAB (p < 0.05). Moreover, LAB were significantly positively correlated with NH3-N, LA and AA, but yeast was significantly negatively correlated with LA (p < 0.05).

3.5. Quality Evaluation of Silage

3.5.1. Sensory Evaluation of Silage

The scoring method of the German Agricultural Association (Deutsche Landwirtschafts Gesellschaft) was used to divide the silage into four grades (i.e., excellent, better, medium, and corrupt) according to the smell, color, and structure of the silage. Figure 3 shows that as the amount of S. guianensis increased, the sensory quality of the mixing silage was also improved. S0 exhibited a pungent sour taste, looser, yellowish-brown color, and medium evaluation grade. S15 had a weak sour smell, a slightly loose texture, tawny color, and a better rate. S30 was excellent and exhibited an aromatic smell, a hazel color, and the loosest texture. But S45 had a pungent aroma, light ammonia flavor, looser texture, brown color, and medium evaluation grade.

3.5.2. Fermentation Evaluation of Silage

The results of the evaluation criteria based on the proportion of organic acids in silage are shown in Table 3. There was no significant difference in the proportion of butyric acid among the groups (p > 0.05). Compared with S0, the percentage of lactic acid in other groups significantly increased (p < 0.05). In addition, the percentage of acetic acid increased with the increase in S. guianensis, and the ratio of S30 and S45 was significantly higher than that of S0 and S15 (p < 0.05). According to the proportion of these organic acids, the total score of each group can be calculated. Although the total score of S15 was significantly higher than that of other groups (p < 0.05), the value of each group was more than 81, indicating that the silage quality of each group was excellent.

3.5.3. Principal Component and Comprehensive Analysis

Principal component analysis was performed on the comprehensive indexes such as nutritional compositions, fermentation characteristics and microbial population in silage samples. The results showed that the cumulative contribution rate of the four principal components (eigenvalue greater than 1) reached 87.413%, which means that this analysis can retain 87.413% of the comprehensive index information (Table 4). Among them, CP, DM, ANF and WSC have larger load values on the principal component 1, and their weight coefficients were 0.915, 0.898, −0.844 and 0.779, respectively. The largest load weight coefficients on the principal component 2 were yeast (0.870), LA (−0.786) and NH3-N (0.692), respectively. Furthermore, AA (0.674) and pH (0.602) had the largest loading weight coefficients on principal component 3. On principal component 4, BA had a higher load value, and its weight coefficient was up to −0.779. To evaluate the difference in silage quality in each group, we further calculated the principal component score. The results showed that there was no significant difference among the other principal components except the principal component 2 (p < 0.05). In addition, the results showed that S15 had higher scores in principal component 1 and principal component 3, while S45 had higher scores in principal component 2 and principal component 4 (Table 5). Combined with the variance contribution rate of each group, the comprehensive scores were calculated and the results showed that: S45 > S30 > S0 > S15 (Table 5). The principal component analysis also showed that the order of silage quality was S15, S0, S30, S45.

4. Discussion

This study systematically compared the effects of different proportions of S. guianensis on nutrient composition and fermentation quality of P. sinese mixed silage. S. guianensis, in this study, had relatively higher DM and CP than P. sinese in fresh materials. DM gradually increased as the proportion of S. guianensis increased after 30 days of ensiling. This result indicated that the nutrient losses of S. guianensis and P. sinese were lower in the mixed silage process. Similar studies have shown that leguminous silage can significantly improve DM intake and ruminant performance compared with gramineous silage [36]. The DM and CP contents in S15–S45 increased and were significantly higher than S0, showing that the nutritional value of mixed silage was improved. Lai et al. also showed that the mixed silage of leguminous pasture and P. sinese had relatively high DM and CP contents [21]. Compared with S0, the NDF of each treatment group decreased significantly, implying that the mixed silage was effective in improving the palatability and utilization of the feed. This result is consistent with the study of Mustafa et al. [37]. ADF is a key indicator of the evaluation of feed energy, and reducing ADF is related to the degradation of cellulose, hemicellulose, and lignin in the fermentation process [15]. In the present study, the ADF in each mixed silage treatment was lower than in S0, which indicated that mixed silage of S. guianensis and P. sinese can be beneficial to improve the digestibility of feed and forage value.
Good silage quality is related to the pH, organic acids, water content, WSC, LAB and yeast populations [36]. A pH level of less than 4 is an important index to evaluate the quality of silage, which can be beneficial to preserving the silage feed for a long period by restricting the growth of undesirable microbes [38]. In the current study, the pH levels of S15 and S30 decreased to below 3.6, thus satisfying the requirements of good silage. The S0 group had lower pH and higher LA content, which was related to the higher content of WSC and higher LAB population in the raw materials. The WSC content provided sufficient fermentation substrates for the growth of LAB, which produce LA and thus decrease the pH of the silage feed [39]. Thus, low pH inhibited undesirable microbial growth and produced good-quality silage feed.
Organic acids are involved in regulating the changes in the microbial community structure during silage fermentation, which can inhibit the growth and reproduction of undesirable microorganisms such as yeast and mold, thereby improving the stability of silage and reducing the loss of nutrients [40]. Among them, LA is a desirable fermentation product in silage produced mainly by LAB-consuming WSC, while AA, PA and BA are undesirable fermentation products [41]. The LA content in each treatment was higher, indicating that LAB was the dominant bacteria in the silage process, consistent with the greater LA population detected in every treatment. The LA/AA ratio is generally used as a qualitative index of fermentation, and good silage fermentation usually results in a ratio of about 2.5 to 3.0 [42,43]. In the present study, the LA/AA value of each treatment was greater than 2.5, and the LA content in S0 was the highest, which was consistent with the results of the lowest pH and most LAB in every treatment group. Moreover, compared with the other treatments, S45 had the least BA content, indicating the least degree of corruption. This phenomenon may be because the LA in S45 inhibited the production of BA. The NH3-N in the silage can reflect the degree of decomposition of protein and AA. The higher the ratio is, the worse is the quality of the silage [44]. In the present study, the NH3-N of each treatment was less than 100 g/kg, which met the standard of good silage. As the amount of S. guianensis increased, NH3-N increased and WSC content decreased. Jacobs described that silage alone in leguminous forage will produce large amounts of NH3-N and BA [45]. Pursiainen and Tuori also found that with the increase in legume, the content of NH3-N increased in grass and legume mixed silage [46]. The NH3-N in S30 was significantly different from those of other treatments, and S45 had the highest content of NH3-N. These results indicated that the degree of decomposition of protein or AA in S45 was the highest, and the nutrient loss of the nitrogen-containing substances in silage was the highest. The WSC content in the mixed silage gradually increased as the proportion of S. guianensis increased, which may be consistent with the fact that the low water activity of the leguminous forage inhibited the activity of LAB in the silage feed and decreased the LA content. This phenomenon led to a decrease in WSC consumption, which is consistent with the research results of Wang et al. [47].
The nutritional, microbiological, nutritional and sensory components of silage can be used to evaluate its fermentation quality, or to explain or predict its impact on the production performance and health attributes of ruminants or their milk products [43,48]. In this study, with the increase in the amount of S. guianensis in mixed silage, its sensory quality also improved, and the S30 group reached the maximum value. However, further evaluation of the proportion of organic acids in silage found that with the increase in S. guianensis in mixed silage, the total score of silage increased first and then decreased, and the maximum value appeared in group S15. Silage fermentation is a complex biochemical process through lactic acid fermentation to achieve low pH and maintain anaerobic conditions [49]. Due to differences in silage raw materials, the environment and evaluators, the results of sensory evaluation may vary depending on the color, smell and texture of the fermentation. In addition, there is a complex relationship between nutritional, microbial and nutritional components in the silage process [39]. For example, our study found that DM was significantly positively correlated with CP, pH and LAB. LAB was also positively correlated with NH3-N, LA and AA, but yeast was negatively correlated with LA. Therefore, the fermentation quality cannot be evaluated comprehensively based on the differences between one or two components. Principal component analysis (PCA) is a general statistical method that transforms multiple indicators into several comprehensive indicators by using the idea of dimensionality reduction while retaining the original information to a large extent [50,51]. This type of analysis has been widely used in the field of animal breeding [52,53], such as reducing the size of the direct additive genetic covariance matrix in multi-trait models [54], or studying the relationship between certain traits of animals and predicted breeding values [55]. In this paper, PCA was applied to analyze the 13 variable indexes of different concentrations of S. guianensis mixed P. sinese silage into 4 independent components, which retained 87.413% of the original variable information. Interestingly, principal component 1 was significantly correlated with the contents of CP, DM, ANF and WSC, while principal component 2 was significantly correlated with the contents of yeast, LA and NN3-N. Principal component 3 shows a large correlation with the contents of AA and pH, while principal component 4 shows a large correlation with the contents of BA. According to the comprehensive scores of PCA, S15 had the highest score, followed by S0, and S30 and S45 had the lowest score, which was consistent with the results of the previous analysis of the proportion of organic acids. Similar studies have also shown that legumes can improve the quality of mixed silage, and a high proportion of legumes can further improve the nutritional value of silage, but may also reduce the quality of silage [56]. In this study, it is feasible to improve the nutritional value of P. sinese fermentation by replacing the appropriate proportion of S. guianensis in silage, but the high proportion will reduce the quality of the silage.

5. Conclusions

The results of this study showed that the contents of DM, CP, NH3-N, AA, and pH increased significantly in silage feed as the amount of S. guianensis increased, but the LA, ADF, LAB and yeast content decreased. The results indicated that the mixed fermentation of S. guianensis and P. sinese can improve the nutritional value of silage, but the high proportion of S. guianensis may reduce the fermentation quality. Hence, the results of fermentation quality and nutritive value suggest that the most suitable ratio of S. guianensis to P. sinese is 30:70. This study provides a new feasible strategy for the development and utilization of high-quality forage resources and solving the problem of annual roughage supply for ruminants. However, further studies are needed to determine the effect of different silage additives on the fermentation quality of mixed silage of S. guianensis and P. sinese. In addition, feeding studies should be conducted to verify their effects on animal production levels.

Author Contributions

Conceptualization, Y.Y. and J.H.; Formal analysis, Q.W. and W.P.; Methodology, H.L. and M.Z.; writing—original draft preparation, Y.Y. and Q.W.; writing—review and editing, J.H. and H.Z; supervision, K.W. and X.H.; project administration, J.H.; funding acquisition, H.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported financially by the Central Public-interest Scientific Institution Basal Research Fund (No:1630102023003, 1630102023008, 1630102023009) and Special Fund for Agricultural Product Quality and Safety of Ministry of Agriculture and Rural Affairs of China: “Evaluation and Analysis of Quality and Safety of Tropical and Subtropical New Feed Resources” (16230077).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are available upon request from the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. The lactic acid bacteria and yeast population of silage prepared with mixtures of S. guianensis and P. sinese for 30 days. Note: Means with different superscript letters in a row were significantly different (p < 0.05).
Figure 1. The lactic acid bacteria and yeast population of silage prepared with mixtures of S. guianensis and P. sinese for 30 days. Note: Means with different superscript letters in a row were significantly different (p < 0.05).
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Figure 2. Correlation among nutritional compositions, fermentation characteristics and microbial population of silage prepared with mixtures of S. guianensis and P. sinese for 30 days. Note: * means significantly correlated (p < 0.05).
Figure 2. Correlation among nutritional compositions, fermentation characteristics and microbial population of silage prepared with mixtures of S. guianensis and P. sinese for 30 days. Note: * means significantly correlated (p < 0.05).
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Figure 3. Sensory evaluation of silage quality of S. guianensis and P. sinese for 30 days.
Figure 3. Sensory evaluation of silage quality of S. guianensis and P. sinese for 30 days.
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Table 1. Nutritional compositions of silage prepared with mixtures of S. guianensis and P. sinese for 30 days.
Table 1. Nutritional compositions of silage prepared with mixtures of S. guianensis and P. sinese for 30 days.
ItemTreatmentsSEMp-Value
S0S15S30S45LinearQuadraticCubic
DM (%FM)19.69 c20.53 bc21.48 ab22.66 a2.390.020.050.13
CP (%DM)11.62 d12.42 c13.39 b14.23 a3.140.050.150.30
WSC (%DM)0.700.710.710.710.610.680.910.98
NDF (%DM)60.3259.8160.1060.103.360.940.970.99
ADF (%DM)47.71 a45.54 b44.70 c42.29 d7.390.020.060.13
Note: Means with different superscript letters in a row were significantly different (p < 0.05). Abbreviations: DM, dry matter; FM, fresh matter; CP, crude protein; WSC, water-soluble carbohydrate; NDF, Neutral detergent fiber; ADF, acid washing fiber; SEM, standard error of mean.
Table 2. Fermentation characteristics of silage prepared with mixtures of S. guianensis and P. sinese for 30 days.
Table 2. Fermentation characteristics of silage prepared with mixtures of S. guianensis and P. sinese for 30 days.
ItemTreatmentsSEMp-Value
S0S15S30S45LinearQuadraticCubic
pH2.82 b2.94 b3.03 ab3.21 a0.23<0.010.010.03
NN3-N (g/kg TN)52.88 c61.53 b64.87 b75.16 a3.28<0.01<0.01<0.01
LA (g/kg DM)38.5437.2136.3335.722.920.110.280.48
AA (g/kg DM)12.44 bc12.01 c13.81 ab14.00 a1.30<0.010.030.02
LA/AA (g/kg DM)3.09 a3.10 a2.64 b2.57 b0.15<0.01<0.01<0.01
PA (g/kg DM)7.11 a2.92 c3.88 b3.97 b0.21<0.01<0.01<0.01
BA (g/kg DM)0.340.450.380.280.150.410.150.26
Note: Means with different superscript letters in a row were significantly different (p < 0.05). Abbreviations: NN3-N, ammonia nitrogen; TN, total nitrogen; LA, Lactic acid; AA, Acetic acid; PA, Propionic acid; BA, Butyric acid; SEM, standard error of mean.
Table 3. Fermentation evaluation of silage quality of S. guianensis and P. sinese for 30 days.
Table 3. Fermentation evaluation of silage quality of S. guianensis and P. sinese for 30 days.
ItemsTreatmentsSEMp-Value
S0S15S30S45
Percentage of lactic acid in total acid/%65.72 b70.71 a66.68 a66.14 a2.75<0.01
Percentage of acetic acid in total acid/%21.40 b22.86 b25.46 a25.96 a2.39<0.01
Percentage of butyric acid in total acid/%0.590.870.700.520.270.21
Total score87.80 b91.20 a86.00 b85.55 b3.30<0.01
Note: Means with different superscript letters in a row were significantly different (p < 0.05). Total scores of 100–81, 80–61, 60–41, 40–21, and 20–0 represent excellent, good, medium, low, and poor silage quality, respectively.
Table 4. Contribution rate and load matrices corresponding to principal components of silage prepared with mixtures of S. guianensis and P. sinese for 30 days.
Table 4. Contribution rate and load matrices corresponding to principal components of silage prepared with mixtures of S. guianensis and P. sinese for 30 days.
ItemsPrincipal Component 1Principal Component 2Principal Component 3Principal Component 4
Eigenvalue5.2602.5172.3901.197
Variance contribution rate/%40.46319.36318.3819.206
Accumulative contribution rate/%40.46359.82678.20787.413
CP0.915−0.034−0.2730.090
DM0.8980.089−0.2910.129
ANF−0.844−0.1660.3610.114
WSC0.779−0.349−0.4150.049
pH0.7430.0650.602−0.110
LAB0.732−0.1450.566−0.095
DNF−0.6290.2370.5640.014
Yeast−0.1220.870−0.2780.286
LA0.317−0.7860.480−0.157
NN3-N0.5460.6920.356−0.069
AA0.2620.3570.6740.261
BA−0.4040.108−0.196−0.779
PA−0.406−0.5340.0080.591
Table 5. Scores of each principal component and comprehensive of silage prepared with mixtures of S. guianensis and P. sinese for 30 days.
Table 5. Scores of each principal component and comprehensive of silage prepared with mixtures of S. guianensis and P. sinese for 30 days.
ItemsScoreComprehensive Score
Principal Component 1Principal Component 2Principal Component 3Principal Component 4
S00.4940.998 a−0.142−0.038−2.214
S15−0.4600.246 ab−0.1660.184−3.154
S300.052−0.458 bc0.138−0.0402.460
S45−0.084−0.786 c0.170−0.1062.908
SEM0.1570.2060.1110.1171.768
p-value0.1960.0030.6210.8520.658
Note: Means with different superscript letters in a row were significantly different (p < 0.05). SEM, standard error of mean.
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Yang, Y.; Wu, Q.; Liu, H.; Wang, K.; Zeng, M.; Han, X.; Peng, W.; Zhou, H.; Han, J. Sustainable Use of Pennisetum sinese: Effect on Nutritional Components and Fermentation Quality of Stylosanthes guianensis in Tropics. Sustainability 2023, 15, 12484. https://doi.org/10.3390/su151612484

AMA Style

Yang Y, Wu Q, Liu H, Wang K, Zeng M, Han X, Peng W, Zhou H, Han J. Sustainable Use of Pennisetum sinese: Effect on Nutritional Components and Fermentation Quality of Stylosanthes guianensis in Tropics. Sustainability. 2023; 15(16):12484. https://doi.org/10.3390/su151612484

Chicago/Turabian Style

Yang, Yuanting, Qun Wu, Hu Liu, Ke Wang, Meng Zeng, Xiaotao Han, Weishi Peng, Hanlin Zhou, and Jiancheng Han. 2023. "Sustainable Use of Pennisetum sinese: Effect on Nutritional Components and Fermentation Quality of Stylosanthes guianensis in Tropics" Sustainability 15, no. 16: 12484. https://doi.org/10.3390/su151612484

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