Effect of substituting copra meal with cassava pomace-urea extrusion in concentrate on the performance of sheep fed on basal rice straw

Efka Aris Rimbawanto, Bambang Hartoyo, Muhamad Bata, Sri Rahayu and Tri Rachmanto Prihambodo

Faculty of Animal Science, Jenderal Soedirman University, Jl. dr. Soeparno Utara 60 Grendeng, Purwokerto-53122, Indonesia
efka.rimbawanto@unsoed.ac.id

Abstract

This study aimed to evaluate the cassava pomace-urea extrusion (CPUE) as a substitute for copra meal (CM), focusing on the nutrient intake, digestibility, nitrogen retention, use efficiency and performance of sheep fed on rice straw as basal feed. A total of 30 thin-tailed rams aged 12 months old (21.8 ± 0.82 kg), were allotted to a Completely Randomized Design with 5 treatment feeds and 6 replicates. The differentiating factor is the use of CPUE to substitute CM in the concentrate by 0, 25, 50, 75 and 100% dry matter (DM). All sheep fed on rice straw ad libitum and concentrate (3% body weight). We conducted a feeding trial for 60 days, which included 14 preliminary days and 6 days dedicated to digestibility testing. The results showed that the DM, organic matter (OM), crude fiber (CF) intake was similar (p>0.05) across feed treatments, except for nitrogen (N) intake which showed an increase (p<0.05). The digestibility of DM, OM, crude protein (CP), CF and total digestible nutrient (TDN) increased (p<0.01), but ether extract (EE) digestibility was similar across treatments (p>0.05). The increased (p<0.01) retention and efficiency of N utilization positively affected (p<0.01) the growth performance and feed conversion when CM was substituted with 75–100% of CPUE. Conclusively, CPUE is a feasible protein source to substitute CM in sheep concentrate.

Key word: daily gain, gelatinization, starch, thin-tail sheep

Introduction

Cassava pomace is solid waste from tapioca production, primarily used for concentrate manufacture in Indonesia (Al Huda et al 2024). In 2022, Indonesia produced 13.6 million tons of cassava, the sixth biggest plant after palm oil, rice, sugarcane, maize and coconuts (FAO 2023). Cassava pomace is used as an energy source for ruminant concentrate because it contains 83.1% TDN, 1.61% CP (Sebastian et al 2021) and 66.9 % DM degradability (effective, 0.05/h^-1) (Chanjula et al 2003).

Sheep farmers in rural areas usually make concentrate feed from materials available locally, such as cassava pomace for energy and copra meal for protein. Copra meal contains 22.4% protein (Al Huda et al 2024), but it is relatively expensive and less favorable due to its rancid smell. Cassava pomace derived from small industry contains relatively higher starch (72.4%) than that from big industry (48.7%) (Abdullah et al 2019), making the former a feasible source of starch for urea starch gelatinization. Moraes et al (2019) report that an alternative source of NPN is the slow-release ammonia produced from starch-urea extrusion. Starch-urea gelatinization is a common alternative to protein source, like soybean meal, that optimizes rural fermentation (Han et al 2022) without harming the production performance of Angus heifer (Fan et al 2024).

While grain is the common source of starch for gelatinization (Helmer et al 1970; Moraes et al 2019; Kozerski et al 2021), cassava is inexpensive, abundant starch in Indonesian rural areas. This study is designed to evaluate the effect of substituting copra meal with cassava pomace-urea extrusion in sheep feed on the consumption, digestibility, nitrogen retention, body weight gain and feed conversion ratio.

Material and methods

Location, Animals, Diets and Experimental Design

The research was undertaken in the Experiment Farm, Faculty of Animal Science, Jenderal Soedirman University, Purwokerto, Indonesia, using 30 thin-tailed rams, aged 12 months old, with an average body weight of 21.8 ± 0.82 kg. Each ram was placed in an individual cage, offered with drinking water. Albenol-100 worming was orally administered to all rams at a dose of 1 ml/12 kg body weight.

The starch content of cassava pomace (Photo 1), analyzed using the 996.11 method (AOAC, 2005), was 58.5% DM. The ratio of cassava pomace starch to urea was 4:1. Every 100 g cassava pomace contained 58.5 g starch, so the urea part (200% CP) would be 14.63%. CPUE was made by mixing cassava pomace and urea at 20% moisture through the extrusion process using a single screw extruder, heating at 100°C then screwing at 700 rpm (Rimbawanto et al 2017). The product was made into pellets with a size of 0.76 cm (Photo 2). The rice straw dan concentrate (rice brand, maize meal, cassava pomace, copra meal and CPUE) were analyzed for DM, ash, CP, EE and CF, according to AOAC method (2005). The results are presented in Table 1.

The experiment was analyzed in a Completely Randomized Design with five treatment feeds and six replicates. The treatments were CM substituted with CPUE by 0, 25, 50, 75 and 100% DM (Table 2). All rams were fed on rice straw ad libitum and concentrate (3% body weight) twice a day at 07.00 AM and 03.00 PM.

Photo 1. Cassava pomace from small industry	Photo 2. Cassava pomace-urea extrusion, (a) pellets with a size of 0.76 cm and (b) powdered form

Sample collection and analysis

Rams body weight was recorded every week. The treatment feed and drinking water was given for 14 preliminary days and 6 days for data collection. Then, feeding and drinking continued for 60 days to observe the effect of treatment feed on ram performance. The recorded data in each treatment were the amount of feed offered, leftover feed before the next feeding, urine and feces. A plastic bag was attached to each ram to contain the urine in order to avoid contamination with the feces. Exactly10 ml of 20% H₂SO₄ was incorporated into each urine container to maintain pH < 3 in the container.

Exactly 10% of the collected sample was put into a plastic bag and stored at -20 °C during data collection. The samples (feed, feed leftover and feces) were oven dried at 60 °C to analyzed for DM, OM, EE and CP, according to AOAC procedure (2005). Urine nitrogen was analyzed with AOAC procedure (2005).

Feed intake was calculated from the total offered feed subtracted by the feed leftover after 24 hours. The apparent digestibility was calculated from the difference between feed nutrient consumed and nutrient in the feces, divided by the feed nutrient consumed. Nitrogen retention was calculated from the differences between N intake and excreted N (feces and urine) and nitrogen use efficiency was calculated by dividing N retention by N intake. The average daily gain (ADG) was calculated based on the differences between the final weight and the initial weight during the maintenance period. Feed conversion ratio (FCR) was calculated based on the feed intake divided by body weight during maintenance.

Statistical analysis

All data obtained from the experiment were subjected to analysis of variance and any difference of mean values across treatments were analyzed with Duncan’s Multiple Range Test using the IBM SPSS Statistics Ver. 26

Result and discussion

The effects of treatment feed on feed consumption and digestibility are presented in Table 3. CPUE, the substitute of copra meal, had similar effects (p>0.05) on DM, OM and CF intake across treatments, except for CP intake which showed an increase (p<0.05). It indicated that CPUE did not affect palatability. In contrast, CP intake increased because the higher the CPUE substitute, the higher the protein feed, despite similar DM intake across treatments (Table 2).

The use of CPUE to substitute CM positively affected (p<0.01) the increase in DM, OM, CP, CF and TDN digestibility, except for EE digestibility (p>0.05). The increase in nutrient digestibility at treatment feeds with 50-100% CPUE indicated a consistent nitrogen release in the rumen, enabling synchronized starch release for better use of ruminal nitrogen for microbial protein synthesis. Zhang et al (2020) reported that the balance release between starch and nitrogen in the rumen can maximize the synthesis of ruminal microbe protein in vitro. Starch-urea gelatinization converts the starch crystal structure into amorphous, thus increasing enzyme accessibility (Han et al 2022; Shen et al 2020) and the starch-urea complex formed during the process can slow down urea hydrolysis in the rumen (Hollό et al 1976). Similarly, other studies reported that the use of slow-release urea (polymer coated-Optigen) in sheep feed has increased dry matter and organic matter digestibility (Geron et al 2016; Sevim and Onol 2019) and protein and fiber digestibility (Manju et al 2022). However, the slow-release urea is not consistently increasing nutrient digestibility since it depends on the dietary formulation or sheep breeds (Geron et al 2016) and balance of feed components, such as fiber and starch (Gardinal et al 2016).

The effect of CPUE substitution for CM on nitrogen retention and nitrogen use efficiency (see Table 4) showed that nitrogen intake increased (p<0.05) while nitrogen excretion in feces and urine remained similar across treatments (p<0.05). Nitrogen retention and nitrogen use efficiency increased (p<0.01) with the use of CPUE to substitute CM.

This study showed that N intake increased with CP content in feed (Table 2), which aligned with the percentage of CPUE to substitute CM. However, it did not affect feces and urinary nitrogen, which indicated the capacity of CPUE to provide carbohydrate and nitrogen for protein synthesis in ruminal microbe. According to Jin et al (2016), the increased N excretion in feces and urine is due to limited activities of ruminal microbe in degrading slow-release urea because there is lack of readily fermentable carbohydrates for the growth and activities of ruminal microbe. Other studies also reported that gelatinization process can synchronize nitrogen availability with carbohydrate degradation, thus reducing nitrogen loss through feces and urine (Estrada-Angulo et al 2016; Geron et al 2018). In this study, CM substituted with 50-100% DM CPUE showed a balanced nitrogen where a substantial amount of nitrogen was absorbed instead of excreted through feces and urine, leading to the best N retention and use efficiency.

Dry matter intake during the 60-day feeding was similar across treatments (p>0.05), but an increase was evident in (p<0.01) final body weight, average daily weight gain and reduce feed conversion ratio (Table 5; Figure 1). Substituting CM with up to 100% DM CPUE did not show different consumption rate due to slow-release nitrogen and reduced ammonia toxicity, leading to a stable ruminal fermentation. Previous studies reported that slow-release urea did not affect dry matter consumption, thus maintaining normal feeding behavior of cows and sheep (Geron et al 2016; Gonçalves et al 2015; Ji et al 2016). The identical findings were reported by Phanthavong et al (2018), indicating that the utilization of ensiled cassava pulp-urea, fresh brewers’ grain and rice straw as feed for local yellow cattle resulted in enhancements in ADG and a decrease in FCR.

Figure 1. Effect of level of CPUE replacing CM (%DM) in the concentrate on ADG and FCR

The most optimum body weight gain was observed in the use of 75–100% DM CPUE to substitute copra meal for ram feed, which resulted in the highest ADG and the lowest FCR. This study has demonstrated that the use of CPUE can increase nutrient digestibility, nitrogen retention and nitrogen use more efficiently, thus contributing to enhanced growth, performance and body weight gain of the rams. These achievements are driven by the use of CPUE which synchronizes nitrogen availability with carbohydrate degradation in the rumen. As a result, the synthesis of microbial protein supports the ram growth. Previous studies have reported that the slow-release urea in sheep feed positively affected ADG and it could substitute of traditional protein sources (Ji et al 2016; Lucena et al 2024; Ma and Faciola 2024).

Conclusion

The results showed that CPUE used as a protein source replacement for copra meal in thin-tailed ram diet, that increases digestibility and nitrogen retention without negative effects on feed intake. Further, it enhanced growth performance of sheep fed on CPUE. In addition, sheep farmers can utilize CPUE for better sheep productivity.

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