The effect of using agricultural industrial waste to replace grass on the efficiency of sustainable lamb production

Endang Purbowati, Retno Adiwinarti, Edy Rianto, Mukh Arifin, Agung Purnomoadi and Vita Restitrisnani

Department of Animal Science, Faculty of Animal and Agricultural Sciences, Universitas Diponegoro, Semarang, Central Java, Indonesia 50275
restitrisnani.vita@gmail.com

Abstract

When replacing grass with agricultural waste in ruminant feed, production efficiency and environmental impact must be considered. This study aimed to determine the effectiveness of lamb production and the environmental effects of substituting grass with agricultural waste. Thirty local male sheep, aged three to five months with an initial body weight of 13.13 ± 1.71 kg, were used. Six sheep were slaughtered at the start of the study to develop linear regression equations for estimating carcass and meat at initial weight. The remaining 24 sheep were given feed until the study ended. The experiment used a completely randomized design with four treatments and six replications. The control ration consisted of a 40:60 grass-to-concentrate ratio (G40). In the treatments, half of the grass (20% of total feed) was replaced with corn cobs (GCob), bagasse (GBag), or peanut shells (GPeas). Parameters measured included methane (CH₄) and nitrogen (N) emissions, feed efficiency and CH₄ and N emissions per unit of product. Data were analyzed using analysis of variance and Duncan’s test. Results showed that GPeas had better feed efficiency than GBag, but was similar to G40 and GCob. GPeas and GCob had slightly higher daily CH₄ emissions than G40 and GBag, though not significantly different. No significant differences were found in CH₄ emissions per dry matter intake (DMI), per average daily carcass weight gain (CWG), or per daily meat weight gain (MWG). CH₄ emissions per body weight gain (BWG) for GPeas were slightly lower than GBag, but both did not differ significantly from G40 and GCob. N emissions per BWG were higher in GBag than in other treatments, but no significant differences were observed in daily N emissions or N emissions per DMI. N emissions per CWG were higher for GBag than for G40 and GPeas, but similar to GCob. N emissions per MWG were higher in GBag than in G40, but not different from GCob and GPeas. The study concludes that peanut shells or corn cobs are better alternatives to elephant grass than bagasse for producing meat efficiently and with lower environmental impact. These findings suggest that alternative feed sources can influence nitrogen emissions and promote environmentally friendly farming practices. Future research should examine the long-term effects of these substitutes on crop yield and soil health.

Keywords: bagasse, corn cobs, methane emissions, N emissions, peanut shells

Introduction

Ruminant feed made from agricultural and industrial waste is widely used around the world. Because of the scarcity of grass during the dry season, ruminants, particularly sheep, have increasingly relied on agricultural waste as a substitute for grass in recent decades (Winugroho, 1999; Sarnklong et al 2010; Yanti and Yayota, 2017). Using agro-industrial waste in animal feed reduces production costs, improves feed quality, ensures a consistent feed supply even during lean seasons and ultimately increases farmers’ profit margins (Sindhu et al 2002). Compared with untreated or urea-treated bagasse, rations containing biologically or biochemically treated bagasse improved feed conversion, dry matter intake and average daily weight gain in Ossimi male lambs (Salama et al 2011). In addition, replacing roughage with ground corn cobs at levels up to 100% did not affect milk yield in crossbred Holstein cows (Wachirapakorn et al 2016). Fermented peanut shells can also replace up to 6% of rice bran in poultry diets (Aka et al 2020). These examples highlight the low cost and potential of agricultural industrial waste to support environmentally friendly and sustainable farming.

Most studies on ruminant feed from agricultural industrial waste have focused on productivity, while fewer have examined emissions released into the environment per unit of product. Research has shown that livestock production negatively impacts the environment through nitrogenous greenhouse gases from nitrogen excreted in urine and feces, ammonia and CH₄ generated by ruminal fermentation. Greenhouse gas emissions, mainly CO₂, CH₄ and N₂O, contribute to global warming and climate change. Methane also depletes ozone, threatening human health, while nitrogen accumulation in soil can alter acidity and reduce biodiversity. Reducing methane and nitrogen emissions from livestock enterprises is therefore critical to maintaining environmental quality and protecting human health (Kustiasih and Medawati, 2017; Panjaitan et al 2015).

Feed made from agricultural waste typically has low nutritional value, characterized by high fiber and low crude protein content (Yanti and Yayota, 2017). This can increase methane emissions (Haryanto and Thalib, 2009; Prayitno et al 2014; Trupa et al 2015). Feeds high in crude fiber generally produce more acetic acid and methane (Prayitno et al 2014; Zhao et al 2016). Beyond feed quality, intake, digestibility and concentrate level are interrelated factors that directly influence enteric CH₄ production (Wang, 2024). Young sheep consuming high levels of protein and energy may also emit more methane and nitrogen (Zhao et al 2016). As energy and nitrogen intake increase, the ratio of nitrogen emissions to production is expected to rise. Prima et al (2019) found that the CP/TDN balance was strongly correlated with nitrogen excretion and weakly correlated with CH₄ emissions. They recommended a CP/TDN ratio of 0.23–0.29 in sheep feed to improve both productivity and environmental performance. Achieving this balance is critical to enhancing sustainability and productivity in sheep farming. Adjusting feed formulations to meet this ratio may reduce greenhouse gas emissions and improve nutrient utilization.

Therefore, research on using agricultural waste as a fiber source instead of grass is necessary to improve sheep production efficiency and environmental sustainability. Implementing such practices could benefit sheep health and contribute to broader agricultural sustainability initiatives. Meeting the evolving demands of the livestock sector while minimizing environmental impacts requires continued investigation into alternative feed sources. This study aimed to evaluate agricultural waste as a fiber source for producing environmentally friendly lamb meat by assessing carcass and meat gain alongside body weight gain, which are important for the lamb production industry.

Materials and methods

The experiment was conducted at the Research Farm of the Faculty of Animal and Agriculture Sciences, Universitas Diponegoro, Semarang, Indonesia. The use of animals and procedures in this study was approved by the Animal Ethics Committee of the Faculty of Animal and Agricultural Sciences, Universitas Diponegoro.

Experimental design, treatments, parameters and animals

Thirty male sheep from Semarang, aged three to five months with an initial body weight of 13.13 ± 1.71 kg, were used. Six sheep were slaughtered at the start of the trial to establish regression equations based on body weight, carcass weight and meat weight. These equations were then applied to estimate the initial carcass and meat weights of the remaining 24 sheep used for feed treatments. The feed consisted of concentrate (rice bran, cassava, soybean meal, molasses and mineral mix) combined with fiber sources such as elephant grass, corn cobs, bagasse and peanut shells (Table 1).

The study employed a completely randomized design with four feed replacement treatments and six replications each. Feed was provided in pelleted form, with grass partially replaced by different fiber sources. Feed and water were supplied ad libitum. The treatment diets were as follows: G40 = 40% elephant grass + 60% concentrate; GCob = 20% elephant grass + 20% corn cobs + 60% concentrate; GBag = 20% elephant grass + 20% bagasse + 60% concentrate; and GPeas = 20% elephant grass + 20% peanut shells + 60% concentrate. Table 2 presents the composition and nutritional value of the diets.

The following parameters were measured: initial body weight; dry matter intake (DMI, g/day; %BW); dry matter digestibility (DMD, %); digestible dry matter intake (DDMI, g/day); crude protein and fiber intake (CPI and CFI, g/day); crude protein and fiber digestibility (CPD and CFD, %); digestible CP and CF intake (DCPI and DCFI, g/day); neutral detergent fiber intake (NDFI, g/day); acid detergent fiber intake (ADFI, g/day); body weight gain (BWG, g/day); carcass weight gain (CWG, g/day); meat weight gain (MWG, g/day); feed efficiency; as well as methane and nitrogen emissions (g/day). Methane emissions per unit of production were also assessed, including CH₄ per DMI (g/g DMI), CH₄ per BWG (g/g BWG), CH₄ per CWG (g/g CWG) and CH₄ per MWG (g/g MWG). Similar calculations were performed for nitrogen, including N emission (g/day), N per DMI (g/g DMI), N per BWG (g/g BWG), N per CWG (g/g CWG) and N per MWG (g/g MWG).

Production performance

Lambs were housed in individual pens. Feed was provided twice daily, in the morning and evening, with feed residue weighed before the morning feeding. Dry matter intake (DMI) was determined by subtracting feed residue from feed offered. Both feed offered and residue were measured on a DM basis. DMI was expressed in kg/day and as a percentage of body weight (BW), indicating intake relative to BW. Nutrient intake (CP, CF, ADF and NDF) was calculated by multiplying DMI by the nutrient content of the diet. Daily body weight gain (BWG) was calculated by subtracting initial BW from final BW, dividing by the feeding period and expressed as g/day. Feed efficiency was calculated by dividing BWG by DMI and multiplying by 100%.

Feed usage

Feed utilization and nutrient levels (CP, CF, ADF, NDF) were determined by comparing DM and nutrient intake with nutrients excreted in feces, urine, and methane. Digestibility was assessed using a 7-day total collection during the feeding period. During this time, all feed, feces and urine were collected, sampled and chemically analyzed.

Total N emission was calculated as the sum of N excreted in feces and urine. Feces and urine were sampled for one week during the treatment period. The digestibility of feed DM, CP and CF was estimated by dividing nutrient intake by nutrient excretion in feces and multiplying by 100%. To determine N emission in feces or urine, fecal or urinary DM output was first calculated and then multiplied by the N concentration in feces or urine.

Methane measurement was conducted immediately after the total collection period. Methane production was measured using the facemask method connected to a methane analyzer (Horiba, Japan) fitted with an airflow meter to determine gas volume, as described by Kawashima et al (2001). Measurements were taken for 10 minutes at 3-hour intervals over three days and results were automatically stored on an IBM-compatible PC. Methane output was recorded in liters per day and then converted to grams.

Slaughtering procedure, carcass and meat measurement

Sheep that had received treatment were slaughtered on the last day of the feeding period. Animals were fasted for 12 hours before slaughter, which was performed using halal techniques in accordance with animal welfare standards. The jugular vein, carotid artery, trachea and esophagus were severed. After bleeding ceased, the head was removed at the atlanto-occipital joint and the legs were cut at the carpo-metatarsal (forelegs) and tarso-metatarsal (hind legs) joints. The tail was removed at the caudal vertebral joint. Skinning was carried out by suspending the hind legs and continued through the abdomen, chest and neck. The viscera were removed after opening the abdominal cavity.

The carcass was weighed to determine hot carcass weight. It was then chilled in a cold room at 16°C for 12 hours before reweighing. A hacksaw was used to divide the carcass symmetrically into two halves along the vertebral column from the cervical vertebrae to the sacrum and both halves were weighed. The right side was further separated into bone, meat, fat and connective tissue, which were weighed individually. Carcass percentage was calculated as hot carcass weight divided by slaughter weight × 100%. Meat weight was determined as carcass weight minus bone weight.

Carcass weight gain (CWG, g/day) and meat weight gain (MWG, g/day) were calculated by subtracting baseline carcass and meat weight from final carcass and meat weight, then dividing by the number of feeding days until slaughter. As BWG is partly composed of CWG and MWG, the proportions of CWG and MWG to BWG were also calculated.

Data analysis

Data were analyzed using ANOVA and Duncan’s multiple range test was applied to determine differences among treatments at the 1% and 5% significance levels (Steel and Torrie, 1991).

Results and Discussion

Among the feed substitution treatments, GPeas had the highest dry matter intake (DMI, kg/day) ( p = 0.001), but GBag and GPeas were similar in %BW, which approached significance ( p < 0.06) (Table 3). This suggests that substituting peanut shells for half of the elephant grass improved palatability, resulting in greater feed intake. G40 and GPeas had higher DM digestibility ( p = 0.007) than GCob and GBag, though they did not differ significantly from each other. This indicates that peanut shells can replace elephant grass without reducing digestibility and even increased digestible DMI ( p = 0.000). DCPI in GPeas was higher (p= 0.122) than in GBag but not significantly different from G40 and GCob. CPI in GBag was significantly lower (p = 0.001) than in GCob, GPeas and G40, while CPD showed no difference (p = 0.725), with an average of 58.7%. Based on the CF, NDF and ADF content of the feeds (Table 2), CFI, NDFI and ADFI differed significantly (p = 0.000) across treatments, ranging from highest to lowest as follows: GPeas, GBag, GCob and G40. Among the treatments, GPeas had the highest NDFI ( p = 0.000). GCob was higher ( p = 0.000) than GBag and G40, while GBag was similar to G40.

Compared with the control (G40), CF digestibility increased when agricultural waste feeds (GCob, GBag and GPeas) were added ( p = 0.002). Under these conditions, digestible CFI increased across all supplemented feeds (p= 0.000). GCob and GBag did not differ, G40 was the lowest and GPeas was the highest (p= 0.000). This effect was likely due to feed being provided in pelleted form and milled, ensuring that the high levels of CF, NDF and ADF did not reduce intake. According to Patil et al (2019), complete feed blocks are high-density, solidified blocks that combine concentrate, forage and supplemental nutrients in appropriate proportions to meet animal requirements. In addition, during natural disasters, this technology can supply livestock with balanced feed. Producing such feeds is essential for improving productivity while utilizing low-cost feed materials.

In line with feed intake and digestibility, GPeas produced greater BWG ( p = 0.008) than GCob and GBag, but was similar to G40. Feed efficiency and daily carcass weight gain (CWG) were lowest in GBag ( p= 0.029 and p = 0.035), although not significantly different from GCob. Feed efficiency did not differ among G40, GCob and GPeas. GBag also had the lowest daily meat weight gain (MWG) ( p = 0.102) compared with G40 and GPeas, but was similar to GCob. However, when CWG and MWG were expressed as a percentage of BWG, no differences were observed ( p = 0.751 and p = 0.766).

These results indicate that replacing 50% of grass with agricultural waste feed often increased sheep production (BWG, CWG and MWG, g/day) and supported normal growth, as reflected by similar CWG and MWG percentages of BWG. Substituting elephant grass with agricultural waste fiber sources (corn cobs, bagasse and peanut shells) produced similar daily methane emissions (p = 0.115), ranging from 14.88 to 18.39 g CH₄/day and similar methane emissions per g DMI (p = 0.385), averaging 0.023 g CH₄/g DMI (Table 4). Daily methane output in this study was slightly lower than the 18.7 g CH₄/day reported by Pinares-Patino et al (2001). GCob and GPeas had lower CH₄ emissions per BWG compared with G40 (p = 0.074), but no differences were found in CH₄ emissions per CWG or MWG (p = 0.207 and p = 0.293).

Substituting elephant grass with agricultural waste fiber sources (corn cobs, bagasse and peanut shells) resulted in similar daily methane emissions (p = 0.115), ranging from 14.88 to 18.39 g CH₄/day and similar methane emissions per g DMI (p = 0.385), with an average of 0.023 g CH₄/g DMI (Table 4). Daily methane output in this study was slightly lower than the 18.7 g CH₄/day reported by Pinares-Patino et al (2001). GCob and GPeas had lower CH₄ emissions per BWG compared with G40 (p = 0.074), but no differences were observed in CH₄ emissions per CWG or MWG (p = 0.207 and p = 0.293, respectively). Overall, CH₄ emissions from agricultural waste fiber feeds were comparable to those from elephant grass, suggesting their potential as alternative feed sources.

The results of N emissions (daily, per DMI, per CWG and per MWG) were not significantly different (p > 0.05), except for N emission per BWG (g N/g BWG), where GBag was highest (p = 0.014), while G40, GCob and GPeas were similar at lower levels (Table 5). This was due to the low BWG in GBag (Table 3). Prima et al (2019) reported that the CP/TDN balance was strongly correlated with N excretion. In this study, the use of agricultural waste as a fiber source for sheep had no effect on nitrogen emissions, likely because the CP/TDN ratio was similar across feeds (0.19–0.21).

The main goal of this study was to evaluate whether GPeas provided higher DMI, DM digestibility, fiber digestibility (CF) and digestible intake of fiber fractions (ADF and NDF), leading to greater feed efficiency, BWG, CWG, and MWG. Higher production in GPeas reduced CH₄ and N emissions per unit of animal output. In contrast, GBag, with lower BWG, CWG and MWG, showed higher CH₄ and N emissions per unit of product. The improved performance of GPeas may be attributed to its protein-to-carbohydrate ratio, particularly the presence of highly digestible carbohydrate (NFE), which supports rumen microbial growth and feed digestion. GPeas feed (Table 2) had a CP/NFE ratio of 0.28 (similar to G40), higher than GBag (0.25), while GCob was intermediate at 0.26.

Conclusion

This study concluded that replacing grass with agricultural waste feed can support sheep production while reducing greenhouse gas emissions. Peanut shells were the most recommended agricultural waste feed in this study, followed by corn cobs, whereas bagasse was not recommended. However, bagasse could be improved as feed by adjusting the protein-to-carbohydrate ratio.

Acknowledgement

The authors thank the Faculty of Animal and Agricultural Sciences, Universitas Diponegoro, for funding this experiment.

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