Comparative Analysis of Rumen Bacterial Profiles and Functions during Adaption to Different Phenology (Regreen vs. Grassy) in Alpine Merino Sheep with Two Growing Stages on an Alpine Meadow

Phenological periods can affect the growth of forage, the single food source for grazing animals, and its nutrition and the stage of growth of the animals can affect the rumen microbiota. The aim of this study was to evaluate the effects of phenological periods (regreen vs. grassy) and growing stages (hoggets (1.5 years old) vs. rams (3 years old)) on rumen bacteria communities and functions in Alpine Merion sheep. The result showed that the Alpha diversity indices of ACE (p < 0.001), Chao (p < 0.001), and Shannon (p < 0.001) were higher in the regreen stage. At the phylum level, the abundances of Bacteroidetes (p = 0.003) and Firmicutes (p = 0.017) shifted with plant phenology. The abundance of fiber-degrading bacteria altered at the genus level (p < 0.05). Genes related to fatty acid degradation and metabolism increased in both the growing stage sheep (p < 0.05). In the grassy stage, the abundance of vitamin B6 metabolism (p = 0.046) was increased in hoggets. In summary, this study showed that the phenological stage had a significant effect on the rumen bacterial compartment and functions in two growing stages, while the growing stage only tended to change rumen bacterial diversity.