Effects of supplementary feeding on the rumen morphology and bacterial diversity in lambs

Early supplementary feeding of lambs before weaning is important to meet their nutritional needs, promote the development of rumen and improve performance. To study the effect of early supplementary feeding on rumen development and the microbiota of lambs, 22 Hu lambs were randomly divided into two groups: one group was fed with milk replacer (group C), and the other group was fed with milk replacer and starter (group S). At 28 days, six lambs in each group were slaughtered, and the rumen content and tissue samples were collected for detection and analysis. The starter significantly promoted the length of rumen papilla (P = 0.03), the concentration of acetate, propionate, butyrate and total volatile fatty acids (TVFA) (P < 0.01), which were higher in group S compared with group C. Group C had a higher rumen microbial diversity than group S. The dominant bacteria in the two groups were the same (Bacteroidetes, Firmicutes and Proteobacteria); however, they differed notably at the genus level. The microbial abundance of the two groups was significantly different for 22 species. In group C, the first three dominant bacteria were Bacteroides, Porphyromonas, and Campylobacter, while in group S they were Succinivibrio, unidentified_Prevotellaceae, and unidentified_Lachnospiraceae. Spearman correlation analysis showed that some ruminal bacteria were closely related to internal environmental factors, e.g., the relative abundances of unidentified_Bacteria, Euryarchaeota, Fusobacteria, and Gracilibacteria correlated negatively with acetate, propionate, butyrate, and TVFA (P < 0.05), while the relative abundances of Firmicutes correlated positively with acetate, propionate, butyrate and TVFA (P < 0.05). Bacteroidetes correlated negatively with propionate, butyrate, and TVFA (P < 0.05); Synergistetes correlated negatively with acetate, propionate, and butyrate (P < 0.05); Deinococcus-Thermus correlated negatively with propionate, butyrate, and TVFA (P < 0.05); Spirochaetes correlated negatively with propionate and TVFA (P < 0.05); and Elusimicrobia correlated negatively with propionate and butyrate (P < 0.05). Actinobacteria and Verrucomicrobia correlated positively correlated with NH₃-N. In conclusion, supplementary feeding of lambs before weaning promoted the development of rumen tissue morphology and rumen microorganisms.