In situ degradation, ruminal fermentation, and the rumen bacterial community of cattle fed corn stover fermented by lignocellulolytic microorganisms

Abstract

Fifteen ruminally-fistulated Jilin Grassland red cattle (shorthorn ♂ × Mongolia yellow cattle♀ F2; 500 ± 10.0 kg) were used to evaluate the effect of corn stover fermented by lignocellulolytic microorganisms on the in situ degradation, ruminal fermentation, and rumen bacterial community. Among them, three cattle were used to determine the kinetic parameters of dry matter (DM) and neutral detergent fiber (NDF) degradation of fermented corn stover (FCS) and corn stover silage (CSS) ensiled with and without lignocellulolytic microorganisms. Twelve cattle were randomly assigned to two groups: the control group fed CSS, and the treatment group fed FCS. The diets consisted of forage (FCS or CSS) and concentrate (corn-soybean meal diet) in a proportion of 60:40 on a DM basis. The FCS group displayed higher effective degradability of DM (p < 0.01) and NDF (p < 0.1) than the CSS group. After feeding for 21 days, the mean ruminal pH was lower in FCS cattle (p < 0.05), but the NH3–N concentration was higher in the FCS group (p < 0.05). The concentrations of ruminal total volatile fatty acids, acetate and propionate were also significantly higher in the FCS group (p < 0.05). There were no differences in the concentration of butyrate or the ratio of acetate-to-propionate between FCS and CSS cattle. Ruminal bacterial diversity was higher in the FCS group (p < 0.05). All samples were dominated by four phyla; Bacteroidetes, Lentisphaerae, Firmicutes and Fibrobacteres, which together accounted for>77% of the total bacterial abundance. Within Bacteroidetes, the abundance of Prevotella increased by 65.6% and 53.1% from day 0 to day 21 in the FCS and CSS groups, respectively. Fibrobacter abundance decreased by 29.9% in the CSS group but changed much less in the FCS group. This study demonstrated a positive effect of microbial inoculants upon the function of cellulose- and hemicellulose-degrading bacteria. We concluded that improvement in the quality of fermented corn stover increases the absorption of nutrients by cattle. Furthermore, FCS altered rumen fermentation by increasing the abundance of the dominant Prevotella genus, and stabilizing the rumen microbial ecosystem.