Effect of a co-fermented amino acid waste liquid-rice bran feed as a soybean meal replacer on growth performance, rumen fermentation, and microbial profile in finishing cattle

Abstract

This study evaluated the effects of replacing soybean meal (SBM) with a co-fermented amino acid waste liquid–rice bran feed on growth performance, rumen fermentation, and rumen fungal community composition in finishing cattle. Forty Simmental bulls with similar initial body weight (499.2 ± 26.1kg, mean ± SD)were assigned to four dietary treatments in a completely randomized design, in which 0% (CON), 10% (T10), 20% (T20), and 30% (T30) of dietary SBM was replaced by the co-fermented feed. The feeding trial lasted 60 days. Growth performance was measured, and rumen fluid was collected from five cattle per treatment on day 30 for fermentation parameter determination and fungal Internal transcribed spacer(ITS) sequencing. Partial replacement of SBM did not significantly affect final body weight and average daily gain (P > 0.05). However, it altered rumen fermentation, as shown by increased propionate and valerate concentrations (P < 0.05), a reduced acetate-to-propionate(A/P) ratio (P < 0.05), and linear increases in acetate, propionate, butyrate, valerate, A/P ratio and total volatile fatty acids(VFAs)(P < 0.05). Fungal community analysis showed that dietary co-fermented feed was associated with changes in rumen fungal composition, including increased relative abundance of Candida and decreased relative abundance of fibrolytic fungi such as Orpinomyces and members of Neocallimastigomycota . In conclusion, replacing SBM with the co-fermented amino acid waste liquid–rice bran feed maintained growth performance while modulating rumen fermentation and fungal community structure. We recommend 20% SBM replacement with the co-fermented feed in finishing beef cattle diets.