The purpose of this study was to evaluate the effect of the availability of cellulase (243U/g, from Neocallistix patriciarum) and the fermentation products of Saccharomyces cerevisiae (yeast products) in the diet on the rumen fermentation characteristics, methane (CH4) emissions and methanogenic bacteria population of growing goats. In this study, 5 Xiangdong black goats were used to design a 5 × 5 Latin square experiment.

The experimental treatment included the control group and two levels of cellulase (0.8 g/kg and 1.6 g/kg DMI respectively, i.e. 194U/kg and 389U/kg DMI), combined with two levels of yeast products (6 g/kg or 12 g/kg DMI). In all treatments, there was no significant difference in feed intake, apparent digestibility of organic matter, neutral detergent fiber and acid detergent fiber. Compared with the control group, the rumen ammonia N concentration of the group added cellulase and yeast products decreased (p=0.001).

After adding cellulase, the activity of cellulase and xylanase decreased. In addition, although the diversity and reproduction number of methanogens in the diet were different in different treatments, the addition of cellulase and yeast products significantly reduced the intestinal CH4 emissions (p<0.05). The current results show that, to a certain extent, the combination of cellulase and yeast fermentation products can reduce the production of CH4 energy and reduce intestinal CH4 emissions.