Effect of mixed microbial silage of mulberry and navel orange residue on growth performance, blood metabolism, and rumen microbiome changes in beef cattle

Mulberry and navel orange residue are limited in practical application due to high moisture content, susceptibility to spoilage, and the presence of minor anti-nutritional factors. The main aim of the present study was to investigate the effect of mixed microbial silage of mulberry and navel orange residue on growth performance, blood metabolism, and rumen microbiome changes in beef cattle. Twenty-four healthy 20–22‑month‑old male Simmental crossbred beef cattle were randomly assigned to four dietary treatments: CON, SQ1, SQ2, and SQ3 groups were fed diets containing 0%, 20%, 30%, 40% of mixed microbial silage, respectively. At the end of the 90-day feeding trial, dietary 30% mixed microbial silage can improve ADG, reduce F/G and serum levels of ALT, UA and TC, increase levels of blood PLT, P-LCC, LYM and EOS in beef cattle ( P < 0.05). The serum MDA level in SQ2 group was significantly lower than that in CON and SQ3 groups ( P < 0.05), while CAT activity was the highest among all treatments ( P < 0.05). Notably, the Shannon, Chao1 and Observed_species indices of the rumen microbiome in SQ3 group were significantly lower than those in CON group ( P < 0.05). The relative abundances of Bacteroidetes and Patescibacteria in SQ3 group were lower than those in CON group ( P < 0.05). Additionally, mixed microbial silage decreased the relative abundance of Proteobacteria and increased that of Actinobacteria. At the genus level, the relative abundance of Cryptobacteroides in SQ1 and SQ2 groups were lower than that in CON group ( P < 0.05), whereas those of SFMI01 and UBA1711 in SQ2 group were increased ( P < 0.05). In addition, significant correlations were observed among growth performance, serum antioxidant capacity and rumen microbiome, and a potential competitive exclusion relationship existed within the rumen microbial community. Collectively, these findings suggested that dietary supplementation with 30% mixed microbial silage of mulberry and navel orange residue could improve growth performance, enhance serum antioxidant capacity and stabilize rumen fermentation of beef cattle. Meanwhile, the altered rumen microbiome may improve growth performance in beef cattle by regulating antioxidant capacity.