Roughage particle size can influence rumen development, which is also determined by rumen microorganisms and their metabolic end-products. Therefore, the aim of this study was to evaluate the comprehensive effects of roughage length and rumen bacterial community on the rumen development of weaned calves. A total of thirty-six weaned Angus female calves (125 ± 3 d; 161.2 ± 13.0 kg) were randomly assigned to three diets differing in roughage particle size: 4 cm (short length); 24 cm (medium length); and 44 cm (long length). Results showed that chopping roughage increased dry matter intake and organic matter apparent digestibility; altered rumen fermentation indicated by the increased rumen butyrate and valerate concentrations; and increased plasma glucose, cholesterol, and total protein. Chopping roughage affected rumen bacterial community, as indicated by altering the diversity indices; by increasing ruminal bacteria Papillibacter and Eubacterium_hallii_group, which are involved in butyrate production; and by increasing Synergistetes and Mogibacterium, which are involved in bacterial colonization. In conclusion, chopping roughage at 4 cm was shown to improve the rumen bacterial community, alter rumen fermentation, eventually promote the development of rumen.

This study determined the effects of wheat stage, preservation treatment, and harvest time on the fermentation characteristics, methane production, and bacterial diversity. In this study, processing wheat into hay can reduce methane production. The MWS7 (wheat harvested at 7:00 in milk stage and preserved as silage) group had a significantly lower CO₂ compared with the DWS15 (wheat harvested at 15:00 in dough stage and preserved as silage) group. Neutral detergent fiber degradation in the hay treatment harvesting at 7:00 was significantly higher than that in other treatments. The butyrate proportion in the DWH7 (wheat harvested at 7:00 in dough stage and preserved as hay) group was higher than that in the MWS7 group. Results from high-throughput sequencing showed that there were differences in the relative abundance of some minor rumen microbiota among the treatments. The MWS7 group had greater microbial diversity and the MWH7 group (wheat harvested at 7:00 in milk stage and preserved as hay) had higher species richness. In addition, the MWH7 group had a lower Methanobrevibacter abundance and methane production. Overall, the MWH7 group may have advantages of rumen fermentation and reduce methane production.