Synergistic effects of Leucaena leucocephala-ginger phytogenic pellet on rumen fermentation, microbial protein synthesis, and enteric methane mitigation in Thai native beef cattle.

Abstract

Background and aim: Enteric methane (CH₄) emissions from ruminants contribute substantially to greenhouse gas accumulation and represent an energy loss that reduces feed efficiency. Phytogenic feed additives rich in bioactive compounds have attracted attention as sustainable alternatives to manipulate rumen fermentation. This study aimed to develop and evaluate a novel Leucaena leucocephala-ginger phytogenic pellet (LGP) and determine its effects on nutrient utilization, rumen fermentation, microbial protein synthesis, and CH₄ mitigation in Thai native beef cattle.

Materials and methods: Four female Thai native beef cattle (230 ± 10 kg) were assigned to a 4 × 4 Latin square design. Animals received a basal diet consisting of concentrate at 1.0% of body weight and rice straw, supplemented with LGP at 0, 50, 100, or 150 g/head/day. Each experimental period lasted 21 days, including 14 days of adaptation and 7 days of sampling. Feed intake, nutrient digestibility, rumen fermentation characteristics, blood metabolites, microbial populations, and microbial protein synthesis were evaluated.

Results: LGP supplementation did not affect feed intake, ruminal pH, ammonia nitrogen concentration, or blood urea nitrogen levels (p > 0.05). However, supplementation improved dry matter digestibility, increasing from 55.4% to 60.0%, and neutral detergent fiber digestibility, increasing from 60.1% to 67.6% (p < 0.05). The highest supplementation level (150 g/head/day) increased ruminal propionate concentration to 28.8 mol/100 mol and enhanced bacterial populations and microbial protein synthesis, reaching 68.1 g N/day (p < 0.05). Protozoal counts declined to 4.8 × 10⁶ cells/mL, accompanied by a reduction in estimated CH₄ production to 23.7 mM/L (p < 0.05). No adverse health effects or clinical signs associated with mimosine toxicity were observed throughout the experiment.

Conclusion: Supplementation with LGP at 150 g/head/day effectively improved rumen fermentation efficiency, enhanced fiber utilization and microbial protein synthesis, increased propionate production, and reduced protozoal populations and enteric CH₄ formation. These findings demonstrate the synergistic potential of L. leucocephala and ginger as a practical phytogenic feed additive to improve rumen function and promote environmentally sustainable beef production under tropical conditions. Further long-term studies involving direct CH₄ measurements and production performance evaluations are warranted.