Effects of active dry yeast on growth performance, rumen fermentation characteristics and slaughter performance in beef cattle

Abstract

This study aimed to investigate the effects of active dry yeast (ADY) on rumen microbial composition and slaughter performance of beef cattle. Thirty-two finishing beef cattle (simmental crossbred cattle ♂ × cattle-yaks ♀), with an average body weight of 110 ± 12.85 kg, were randomly assigned to one of four treatments: the low plane of nutrition group (Control), low plane of nutrition group + ADY 2 g/head/d (ADY2), low plane of nutrition group + ADY 4 g/head/d (ADY4) and high plane of nutrition group (HPN). ADY supplementation increased average daily gain (P<0.001), and the carcass weight of ADY4 group had no significant difference with HPN group (P>0.05). The serum glutamic-pyruvic transaminase activity in control and ADY4 group was higher than HPN group (P=0.001). The neutral detergent fiber (P=0.022) and acid detergent fiber (P=0.043) digestibility in HPN group was greater than control, but no difference was obtained among ADY2, ADY4 and HPN group (P>0.05). The rumen ammonium nitrogen content in control was greater than ADY2 and ADY4 group (P=0.003), and no difference was obtained ADY2, ADY4 and HPN group (P>0.05). The propionic acid content in the rumen in ADY2, ADY4, and HPN group were greater than control group (P<0.001). The simpson (P=0.014) and shannon (P=0.045) indexes in control and HPN group were greater than ADY4 group. At the phylum level, the relative abundance of Firmicutes in the HPN group was higher than ADY4 group (P=0.015). At the genus level, HPN and ADY4 were clustered together, and the relative abundance of Ruminococcaceae UCG-002 in ADY4 group was higher than control and HPN group (P=0.004). In conclusion, supplementation ADY 4 g/head/d shift the rumen microbial composition of beef cattle fed low plane of nutrition to a more similar level with cattle fed with HPN diet, produced comparable carcass weight with HPN diet.