Optimizing goat growth and rumen function with monosodium glutamate byproduct-treated rice straw in total mixed rations.

Background and aim: Rice straw is a widely available but nutritionally limited roughage for ruminants due to its low protein content and digestibility. This study aimed to evaluate the effects of replacing pangola hay with monosodium glutamate byproduct-treated rice straw (MSGBTRS) in total mixed rations (TMR) on growth performance, nutrient utilization, rumen fermentation, and microbial populations in fattening goats.

Materials and methods: Sixteen male Anglo-Nubian crossbred goats (3 months old, 15 ± 2 kg) were randomly allocated to four dietary treatments (0%, 25%, 50%, and 75% MSGBTRS replacing pangola hay) in a completely randomized design. MSGBTRS was prepared by blending rice straw with liquid MSGB (8.8:1.2 w/w) and sun-dried. The feeding trial lasted 50 days, followed by a 7-day digestibility study. Feed intake, body weight (BW), rumen fluid, blood, and fecal samples were analyzed. Rumen microbiota was quantified through real-time polymerase chain reaction.

Results: The 25% MSGBTRS group achieved the highest BW gain (6.52 kg; p = 0.034). Dry matter intake declined linearly with increased MSGBTRS levels (p = 0.019). Neutral detergent fiber and acid detergent fiber digestibility were significantly reduced at 75% substitution (p = 0.001). Ruminal ammonia nitrogen concentrations increased with MSGBTRS inclusion, peaking at 75% (19.08 mg/dL; p = 0.029), while blood urea nitrogen remained unaffected. The 25% group exhibited optimal propionate and butyrate levels and a favorable acetate-to-propionate ratio. Total bacterial populations were highest in the 50%-75% groups (p = 0.002), with the greatest Ruminococcus albus abundance in the 75% group (p = 0.045).

Conclusion: Substituting pangola hay with 25% MSGBTRS in TMR is optimal for improving growth performance and fiber digestibility in goats, without adverse effects on feed intake or rumen fermentation. MSGBTRS presents a sustainable, cost-effective alternative roughage source, supporting zero-waste livestock production. Future studies should explore long-term impacts on carcass traits, health, and economic viability in larger-scale goat systems.