| Livestock Research for Rural Development 37 (4) 2025 | LRRD Search | LRRD Misssion | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
This study evaluated the effects of incorporating Jack bean plants (Canavalia ensiformis) into oil palm frond silage on nutrient composition, fermentation quality, rumen degradability and methane emissions using an in vitro system. Silage mixtures were formulated with 0%, 25%, and 50% Jack bean inclusion. Increasing Jack bean levels significantly (p< 0.05) enhanced crude protein content (9.55% to 12.32% DM) while reducing fiber fractions, including NDF, ADF, and lignin, indicating improved silage digestibility. All silages were well preserved, as shown by low dry matter (DM) loss (1.28–1.83%), low pH (4.02–4.42), low ammonia nitrogen (0.06–0.14% DM), and high Flieg point scores (119.48–129.50). Higher Jack bean inclusion increased (p<0.05) total short-chain fatty acids and rumen ammonia, leading to significantly greater dry matter and organic matter degradability. Conversely, methane production decreased sharply (p<0.05), from 4.58% to 1.67% of the total gas. These findings demonstrate that Jack bean inclusion improves silage quality, enhances nutrient utilization, and reduces environmental impact by lowering methane emissions. Optimal performance was achieved with a 50% Jack bean inclusion, which balances protein enrichment and methane mitigation.
Keywords: antinutritional factors, greenhouse gas mitigation, silage quality, sustainable feeding strategies, tropical forage
Forages are a vital component of ruminant diets, providing essential nutrients for maintenance, growth and production (Ridla and Nahrowi 20025). However, in tropical regions like Indonesia, the consistent availability of high-quality forage is often constrained by seasonal fluctuations, leading to feed shortages, particularly during the dry season (Kumalasari et al 2025). One potential solution is the utilization of agricultural by-products as an alternative forage source (Ridla et al 2025a). Oil palm fronds, generated through routine pruning, are produced in large quantities due to Indonesia’s extensive oil palm industry (Ridla et al 2023a). In 2024, national oil palm production reached 47,474 tons, producing approximately 10.4 million tons of frond waste annually (BPS 2024). This biomass represents a sustainable and low-cost resource for ruminant feeding.
Despite its abundance, oil palm fronds have low nutritional value, such as low crude protein (CP) and high levels of structural carbohydrates, such as neutral detergent fiber (NDF) and acid detergent fiber (ADF), which limit digestibility and rumen microbial activity (Ridla et al 2023a). Combining oil palm fronds with high-protein forages is essential to enhance their feeding value. Jack bean plants (Canavalia ensiformis) are a promising option due to their high biomass yield and crude protein content ranging from 17.32% to 19.91% at 55 to 90 days after planting (Bayu et al 2025). However, Jack bean plants contain hydrogen cyanide (HCN), an antinutritional factor that can be toxic if not properly managed (Alifianty et al 2023).
Silage production is an effective method to preserve forage while reducing antinutritional compounds through microbial fermentation (Wang et al 2022). Proper silage fermentation requires sufficient water-soluble carbohydrates (WSC) as a substrate for lactic acid bacteria (LAB). Since oil palm fronds are low in WSC, adding external carbohydrate sources, such as cassava pulp and tofu waste, can enhance fermentation quality and silage stability (Ridla and Nahrowi 2025; Ridla et al 2023a).
Beyond improving feed quality, ruminant nutrition strategies must also consider environmental sustainability, particularly methane (CH₄) emissions from enteric fermentation, a significant source of greenhouse gases (Ridla et al 2023b; Ridla and Nahrowi 2025). High-fiber, low-digestibility forages typically increase CH₄ production, making it crucial to evaluate how mixed silages impact rumen fermentation and methane emissions (Ridla et al 2023b; Ridla et al 2025b).
To date, limited research has explored the combined use of oil palm fronds and Jack bean plants in silage production. Therefore, this study aimed to evaluate silage quality, in vitro rumen degradability, and methane emissions of mixed silages formulated from oil palm fronds and Jack bean plants, supporting the development of sustainable feeding strategies using underutilized agricultural by-products.
Oil palm fronds and Jack bean plants were used as the primary materials for silage production. Both forage materials were cultivated at the experimental plantation of IPB University, located in Jonggol, Bogor, Indonesia. The oil palm fronds were collected as a by-product of routine pruning, while the Jack bean plants were harvested at the vegetative stage to ensure optimal nutrient content (90 days after planting). The materials were chopped into 1-2 cm pieces using a mechanical chopper and mixed at predetermined ratios.
The silage was prepared by mixing oil palm fronds and Jack bean plants at different ratios. Glucose (spoiled sugar) was added at 5% of dry weight as an external water-soluble carbohydrate (WSC) source to support lactic acid bacteria (LAB) fermentation. Approximately 500 g of each mixture was tightly packed into anaerobic silos (polyethylene bottles), ensuring minimal air pockets, and sealed to prevent oxygen penetration. The silos were stored at room temperature (27-30 °C) for 40 days to allow fermentation.
The experiment followed a completely randomized design (CRD) with three treatments and five replicates per treatment:
T1. Oil palm fronds silage only (control).
T2. Mixed silage of oil palm fronds and Jack bean plants (75:25 fresh basis).
T3. Mixed silage of oil palm fronds and Jack bean plants (50:50 fresh basis).
After 40 days, the silages were opened for analysis of fermentation characteristics, chemical composition. In addition, in vitro rumen fermentation, gas production, methane emission, and dry and organic matter degradability were also evaluated
Samples were dried at 60 °C for 48 h and ground through a 1-mm screen for subsequent analyses. The following parameters were determined: dry matter (DM), crude protein (CP), ether extract (EE), crude fiber (CF), and crude ash using AOAC (2015) official methods. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were analyzed following AOAC (1990). Hemicellulose was calculated as NDF-ADF. Water-soluble carbohydrate (WSC) content was measured using the anthrone-sulfuric acid method (Deriaz 1961). Hydrogen cyanide (HCN) levels were determined using the Volhard argentometric method (AOAC 2015).
The pH of the silage was measured using a digital pH meter (Horiba-18) after extracting 40 g of silage with 400 mL of distilled water, followed by filtration of the extract. Ammonia nitrogen (NH₃-N) concentration was determined according to AOAC (2015). The Flieg score, used to evaluate overall silage quality, was calculated using the formula = 220 + (2 × % dry matter of silage − 15) − 40 × pH as described by Kilic (1986).
Rumen fluid was collected from two rumen-fistulated cattle maintained on a standard diet containing 60% forage and 40% concentrate. The collected fluid was filtered through four layers of cheesecloth while continuously flushed with CO₂ to maintain anaerobic conditions.
The in vitro incubation was performed using the two-stage technique of Tilley and Terry (1963). Approximately 500 mg of silage sample was incubated with 50 mL of buffered rumen fluid in sealed serum bottles at 39 °C. After incubation, the residues were filtered, dried,ashed and weighed to determine in vitro dry matter degradability (IVDMD) and in vitro organic matter degradability (IVOMD).
Additionally, after 4 h of incubation, aliquots were analyzed for pH using a digital pH meter (Horiba-18), ammonia nitrogen (N-NH₃) using the Conway and O’Malley (1942) micro-diffusion method, and total short-chain fatty acids (TSCFA) via steam distillation following Kromann et al (1967).
Gas production was measured at 3, 6, 12, 24, and 48 h using a gas-tight syringe. At 48 h, the total gas volume was recorded, and a 5 mL gas sample was collected for methane (CH₄) analysis using gas chromatography, following the protocol of Theodorou et al (1994).
All data were analyzed using one-way ANOVA in SPSS version 25.0 (IBM Corp 2017). The differences among treatment means were analyzed using Tukey's Honestly Significant Difference (HSD) test to determine pairwise comparisons at a significance level of p < 0.05. Results are presented as mean ± standard deviation (SD).
The chemical composition of oil palm fronds and Jack bean plants is shown in Table 1. Oil palm fronds exhibited higher fiber fractions, including NDF (66.57%), ADF (27.85%), and hemicellulose (38.71%), indicating low digestibility and limited energy availability. In contrast, Jack bean plants contained higher crude protein (15.56%) and lower fiber content (NDF 40.33%), making them a valuable protein source for ruminant diets. However, the presence of hydrogen cyanide (HCN) at 303.24 ppm in Jack bean plants poses a potential toxicity risk if not adequately processed or mixed with other forages. Therefore, ensiling oil palm fronds with Jack bean plants can help balance protein and energy levels while enhancing overall feed quality and safety.
|
Table 1. The chemical composition of oil palm fronds and Jack bean plants |
|||
|
Parameter |
Oil palm fronds |
Jack bean plants |
|
|
Dry matter (DM), % |
33.07 |
30.15 |
|
|
Ash, % DM |
10.00 |
8.31 |
|
|
Crude protein, % DM |
8.72 |
15.56 |
|
|
Ether extract, % DM |
4.50 |
4.02 |
|
|
Crude fiber, % DM |
35.64 |
31.28 |
|
|
Nitrogen-free extract, % DM |
41.14 |
40.83 |
|
|
Neutral detergent fiber, % DM |
66.57 |
40.33 |
|
|
Acid detergent fiber, % DM |
27.85 |
26.72 |
|
|
Hemicellulose, % DM |
38.71 |
13.62 |
|
|
Cellulose, % DM |
19.36 |
18.45 |
|
|
Lignin, % DM |
7.47 |
7.40 |
|
|
Water-soluble carbohydrates, % DM |
1.39 |
1.24 |
|
|
Hydrogen cyanide, ppm |
- |
303.24 |
|
The inclusion of Jack bean plants in silage mixtures significantly (p<0.05) influenced nutrient composition (Table 2). Increasing Jack bean levels from 0% to 50% resulted in a progressive rise in crude protein content, from 9.55% to 12.32% DM, demonstrating its value as a protein-rich forage. In contrast, crude fiber, NDF, ADF, cellulose, and lignin concentrations decreased (p<0.05) with higher Jack bean inclusion, indicating improved degradability and potentially greater nutrient availability for ruminants. Water-soluble carbohydrates (WSC) ranged from 4.10% to 4.47% DM, providing sufficient substrate to support lactic acid bacteria activity during fermentation, which enhances silage preservation and quality. However, hydrogen cyanide (HCN) was detected at 90.94 ppm in the 25% inclusion level and increased to 140.84 ppm at 50%, posing potential toxicity risks if not carefully managed. Overall, Jack bean inclusion improves nutrient balance and silage quality, but proper control of HCN levels is essential for safe utilization.
|
Table 2. The chemical composition of mixed silages |
||
|
Parameter |
Jack bean plants' inclusion |
Values |
|
Dry matter (DM), % |
0 |
36.21 ± 3.00 |
|
25 |
35.44 ± 0.79 |
|
|
50 |
37.56 ± 1.09 |
|
|
Ash, % DM |
0 |
10.78 ± 1.19b |
|
25 |
9.66 ± 0.84a |
|
|
50 |
9.48 ± 0.55a |
|
|
Crude protein, % DM |
0 |
8.55 ± 0.83b |
|
25 |
11.28 ± 0.16b |
|
|
50 |
12.82 ± 0.25c |
|
|
Ether extract, % DM |
0 |
4.15 ± 0.86 |
|
25 |
4.39 ± 0.65 |
|
|
50 |
4.92 ± 1.08 |
|
|
Crude fiber, % DM |
0 |
30.85 ± 1.07c |
|
25 |
29.56 ± 1.50b |
|
|
50 |
27.46 ± 1.68a |
|
|
Nitrogen-free extract, % DM |
0 |
44.68 ± 1.69 |
|
25 |
45.11 ± 1.57 |
|
|
50 |
45.83 ± 0.94 |
|
|
Neutral detergent fiber, % DM |
0 |
72.25 ± 2.83b |
|
25 |
68.60 ± 1.68a |
|
|
50 |
68.13 ± 1.64a |
|
|
Acid detergent fiber, % DM |
0 |
43.74 ± 3.13b |
|
25 |
41.77 ± 2.17a |
|
|
50 |
41.03 ± 2.30a |
|
|
Hemicellulose, % DM |
0 |
28.51 ± 2.41 |
|
25 |
26.83 ± 1.84 |
|
|
50 |
27.10 ± 2.14 |
|
|
Cellulose, % DM |
0 |
34.11 ± 2.87b |
|
25 |
3 3.09 ± 2.49ab |
|
|
50 |
32.48 ± 2.45a |
|
|
Lignin, % DM |
0 |
9.06 ± 0.76b |
|
25 |
8.24 ± 0.64a |
|
|
50 |
7.98 ± 0.47a |
|
|
Water-soluble carbohydrates, % DM |
0 |
4.10 ± 0.21 |
|
25 |
4.31 ± 0.08 |
|
|
50 |
4.47 ± 0.11 |
|
|
Hydrogen cyanide, ppm |
0 |
- |
|
25 |
90.94 ± 3.32a |
|
|
50 |
140.84 ± 15.01b |
|
|
abcMeans that in the same column, without a common letter, are significant at p<0.05 |
||
The fermentation characteristics of the silages are presented in Table 3. The dry matter (DM) content ranged from 35.44% to 37.56%, which is within the optimal range for desirable fermentation (Ridla et al 2024; McDonald et al 1991). All silages were well preserved, as indicated by their low DM loss, low pH values, low ammonia nitrogen (NH₃-N) concentrations and high Flieg scores (Ridla et al 2025a, Ridla and Nahrowi 2025).
The DM loss ranged from 1.28% to 1.83%, suggesting efficient nutrient conservation during the ensiling process (Ridla et al 2025b). Silage pH values between 4.42 and 4.02 are considered ideal for stable lactic acid fermentation. Similarly, NH₃-N levels were low (0.06% to 0.14% of DM), indicating minimal proteolysis and effective preservation of true protein. The high Flieg score values, 119.48 to 129.50, further confirmed the superior fermentation quality (Ridla et al 2025a; Ridla and Uchida 1998).
Overall, these findings demonstrate that all silages underwent proper fermentation and were effectively stabilized during storage, ensuring both high feed quality and nutrient retention (Muck et al 2018; Kung et al 2018).
|
Table 3. Silage fermentation quality |
|||
|
Parameter |
Jack bean plants' inclusion |
Values |
|
|
Dry matter loss, % |
0 |
1.83 ± 0.30b |
|
|
25 |
1.28 ± 0.61a |
||
|
50 |
1.78 ± 0.56b |
||
|
pH |
0 |
4.42 ± 0.06c |
|
|
25 |
4.09 ± 0.12b |
||
|
50 |
4.02 ± 0.04a |
||
|
Flieg score |
0 |
120.50 ± 5.56a |
|
|
25 |
129.50 ± 4.36b |
||
|
50 |
119.48 ± 2.88a |
||
|
N-NH3,% Total N |
0 |
0.14 ± 0.04 |
|
|
25 |
0.10 ± 0.04 |
||
|
50 |
0.06 ± 0.02 |
||
|
abcMeans that in the same column, without a common letter, are significant at p<0.05 |
|||
The inclusion of Jack bean plants in silage mixtures had a significant (p<0.05) effect on rumen fermentation, degradability, and methane production (Table 4). Rumen pH remained stable across treatments (7.13-7.09), indicating a balanced fermentation environment suitable for microbial activity. Rumen ammonia (NH₃) concentration increased significantly with higher Jack bean inclusion, from 5.79 mM (0%) to 8.98 mM (50%), reflecting greater protein availability from the Jack bean plants (Ridla et al 2025a). Total short-chain fatty acids (SCFA), key indicators of fermentation efficiency, also increased markedly, from 71.78 mM in the control to 137.88 mM at 50% inclusion, suggesting enhanced microbial fermentation (Ridla et al 2025b).
Degradability parameters improved significantly (p<0.05) with the inclusion of Jack bean plants. Dry matter degradability increased from 52.33% at 0% to 64.40% at 50%, while organic matter degradability showed a similar improvement, rising from 51.31% to 63.06%. These results indicate enhanced nutrient utilization due to the higher proportion of digestible forage contributed by Jack bean plants (Ridla et al 2023a). Total gas production also increased significantly, reflecting greater microbial fermentation activity with higher Jack bean inclusion (Ridla and Nahrowi 2025).
|
Table 4. Rumen fermentation, digestibility, and methane production |
|||
|
Parameter |
Jack bean plants' inclusion |
Values |
|
|
Rumen pH |
0 |
7.13 ± 0.04 |
|
|
25 |
7.11 ± 0.04 |
||
|
50 |
7.09 ± 0.05 |
||
|
Rumen ammonia, mM |
0 |
5.79 ± 1.27a |
|
|
25 |
7.35 ± 1.02b |
||
|
50 |
8.98 ± 0.67c |
||
|
Total short-chain fatty acid, mM |
0 |
71.78 ± 12.22a |
|
|
25 |
107.81 ± 10.41b |
||
|
50 |
137.88 ± 10.03c |
||
|
Dry matter degradability, % |
0 |
52.33 ± 2.56a |
|
|
25 |
56.22 ± 1.95b |
||
|
50 |
64.40 ± 2.35c |
||
|
Organic matter degradability, % |
0 |
51.31 ± 2.62a |
|
|
25 |
55.12 ± 1.52b |
||
|
50 |
63.06 ± 2.05c |
||
|
Total gas production, ml/g Dry matter |
0 |
58.56 ± 5.86a |
|
|
25 |
71.24 ± 5.26b |
||
|
50 |
101.53 ± 9.36c |
||
|
CH4, % Total gass |
0 |
4.58 ± 0.68a |
|
|
25 |
2.91 ± 0.56b |
||
|
50 |
1.67 ± 1.08c |
||
|
CH4, % Organic matter digestibility |
0 |
1.41 ± 0.27a |
|
|
25 |
0.64 ± 0.15b |
||
|
50 |
0.31 ± 0.21a |
||
|
abcMeans that in the same column, without a common letter, are significant at p<0.05 |
|||
Interestingly, methane (CH₄) production decreased sharply with increasing Jack bean plant inclusion. CH₄ as a percentage of total gas dropped from 4.58% in the control to 1.67% at 50% inclusion. Similarly, CH₄ production per unit of organic matter digestibility declined, indicating improved fermentation efficiency and reduced energy loss through methane emissions. Overall, incorporating Jack bean plants, a more digestible and nutrient-rich forage, into silage mixtures enhanced rumen fermentation, improved degradability, and promoted environmental sustainability by mitigating methane production (Ridla et al 2023a; Ridla and Nahrowi 2025).
The authors gratefully acknowledge the financial support provided by IPB University through the Skema Riset Aksi, under grant number 15328/IT3.D10/PT.01.03/P/B/2024. This funding was essential for the successful implementation and completion of this research project.
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