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.

作为绿色饲料添加剂，酵母细胞壁（YCW）具有多种生物学功能。但是，关于断奶犊牛中使用YCW作为饲料添加剂的数据有限。该研究旨在评估YCW对断奶小牛的生长性能，瘤胃发酵和微生物群落的影响。将五十只健康的荷斯坦雄性小牛（体重92±8.29 kg，年龄60±5 d）随机分为5组：无YCW的CON，YCW1（YCW占精矿的0.2％），YCW2（0.4％） ，YCW3（0.8％）和YCW4（1.6％）。膳食浓缩物与粗饲料的比例为40:60。每天在0900 h和1600 h定期给所有小牛饲喂两次，并自由饮水。实验持续了60天。在第0天和第60天测量体重。从第57天到第59天，通过直肠采样收集粪便样品。在第60天，12头小牛[CON组的6头小牛；屠宰来自最佳生长表现组（YCW2）的接近该组平均体重的6头小牛，并收集瘤胃液和固体样品。结果表明，YCW2组的平均日增重明显增加（与CON，YCW3和YCW4组相比，P <0.05）。YCW2组的采食量与日平均增重的比率低于CON组（P <0.05）。补充YCW2不会影响总VFA，乙酸盐和丁酸盐的浓度（P > 0.05）。然而，与CON组相比，YCW2组的瘤胃微生物蛋白和丙酸酯含量较高（P <0.05）。YCW2的添加使小牛粪便微生物的总OTU数值增加（P > 0.05），而YCW2组中未培养的拟杆菌S24-7组的相对丰度更高（P <0.05）比CON组高。总之，YCW的膳食补充改善了断奶犊牛的生长性能和瘤胃发酵。结果表明，YCW可以用作促进断奶犊牛健康生长的饲料添加剂，YCW的最佳含量占浓缩物的0.4％。