Effects of feeding Aspergillus oryzae on intestinal and fecal methane emissions, and performance of simmental crossbred steers.

This study aimed to assess the impact of Aspergillus oryzae supplementation on CH₄ emissions and the production performance of beef cattle. Sixteen healthy Simmental crossbred steers (552.4 ± 35.5 kg) were randomly assigned to either a control group (CG, basal diet) or an A. oryzae group (AO, basal diet + 6 g A. oryzae per head daily). CH₄ emissions from enteric fermentation and manure, growth performance, nutrient and energy digestibility, rumen fermentation variables, and microbial populations were evaluated. A. oryzae supplementation did not affect average daily gain (ADG) or dry matter intake (DMI), though ADG increased by 11.1%. AO steers exhibited a 36.4% increase (P < 0.05) in apparent NDF digestibility, a reduction (P < 0.05) in NH₃-N, and elevated rumen fungi and Butyrivibrio fibrisolvens populations while reducing protozoa and methanogens. CH₄ emissions from enteric fermentation and maure decreased by (P < 0.05) 18.8% and 56.6%, respectively. It was concluded that supplementation with A. oryzae effectively lowered CH₄ emissions in both enteric fermentation and manure without compromising beef cattle growth rate.