Abstract The aim of this work was to study the impact of a crude protein (CP) restriction on performance, ruminal fermentation and microbial community composition in fattening Holstein bulls (from 118 to 331 d of age and from 165 to 522 kg body weight [BW]) fed high-concentrate diets. Twenty animals were assigned to two dietary treatments: concentrate CP was formulated either based on the levels used commercially (CTR: 140 g CP/kg dry matter [DM]) or reducing them (LP: 120 g CP/kg DM). Concentrate was supplemented with barley straw and both were supplied ad libitum. Animal BW and concentrate intake were automatically recorded on a daily basis. Feces, urine and ruminal fluid were sampled twice, during the growing period (160 d of age and 225 kg BW) and during the finishing period (280 d of age and 444 kg BW), for digestibility, ruminal fermentation and microbial population characterization. No differences in BW or cumulated concentrate intake were found between treatments, despite the fact that average daily gain was lower in LP group at the beginning of the growing period (P

中文翻译：

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蛋白质限制对饲喂高浓度日粮的荷斯坦公牛性能、瘤胃发酵和微生物群落组成的影响

摘要 本工作的目的是研究粗蛋白 (CP) 限制对育肥荷斯坦公牛（118 至 331 日龄和 165 至 522 公斤体重 [BW] 的性能、瘤胃发酵和微生物群落组成的影响） ]) 喂食高浓度饮食。20 只动物被分配到两种饮食处理：根据商业使用的水平（CTR：140 g CP/kg 干物质 [DM]）或减少它们（LP：120 g CP/kg DM）配制浓缩 CP。浓缩物补充有大麦秸秆，两者都是随意供应的。每天自动记录动物体重和浓缩物摄入量。在生长期（160 天龄和 225 kg BW）和育肥期（280 天龄和 444 kg BW）期间对粪便、尿液和瘤胃液取样两次，以测定消化率，瘤胃发酵和微生物种群特征。尽管 LP 组在生长期开始时的平均日增重较低，但在处理之间未发现 BW 或累积精料摄入量存在差异（P