Effects of yeast cell wall on the growth performance, ruminal fermentation, and microbial community of weaned calves

Abstract

As a green feed additive, yeast cell wall (YCW) has various biological functions. However, there has been limited data on the utilization of YCW as a feed additive in weaned calves. The study was carried out to evaluate the effects of YCW on the growth performance, ruminal fermentation, and microbial community of weaned calves. Fifty healthy Holstein male calves (92 ± 8.29 kg of body weight and 60 ± 5 d of age) were randomly allocated into 5 groups: CON with no YCW, YCW1 (YCW accounted for 0.2% of the concentrate), YCW2 (0.4%), YCW3 (0.8%), and YCW4 (1.6%). The dietary concentrate-to-roughage ratio was 40:60. All the calves were fed regularly twice a day at 0900 h and 1600 h and had free access to water. The experiment lasted for 60 d. Body weight was measured on d 0 and 60. From d 57 to 59, fecal samples were collected by rectal sampling. On d 60, 12 calves [6 calves from the CON group; 6 calves from the optimum growth performance group (YCW2)] that were close to the group average weight were slaughtered, and the ruminal fluid and solid samples were collected. The results showed that the average daily gain of YCW2 group was significantly increased (P < 0.05) as compared to CON, YCW3, and YCW4 groups. The ratio of feed intake to average daily gain in the YCW2 group was lower (P < 0.05) than that in the CON group. The concentrations of total VFA, acetate, and butyrate were not affected (P > 0.05) by YCW2 supplementation. However, the concentrations of ruminal microbial protein and propionate were higher (P < 0.05) in the YCW2 group when compared with CON group. Supplementation of YCW2 numerically increased (P > 0.05) the total OTUs of calves’ fecal microorganisms, and the relative abundance of Bacteroidales S24–7 group uncultured in the YCW2 group was higher (P < 0.05) than that in the CON group. In conclusion, dietary supplementation with YCW improved the growth performance and ruminal fermentation of weaned calves. Results suggest that YCW can be used as a feed additive to promote the healthy growth of weaned calves, and the optimum level of YCW is accounted for 0.4% of the concentrate.