Abstract:

This research aimed to investigate the effects of oat （Avena sativa） cubes， compared to oat hay， on rumen fermentation and microbial composition in sheep. Twelve one year old ram lambs with similar body weight were randomly divided into two treatment groups. One group was fed unprocessed oat hay （OH）， and the other group was fed oat cubes （OC）. The two groups were fed the same quantity of the respective commercial feeds at the same quality. The duration the experiment was 60 days， comprising a feed adaptation period of 10 days and a formal experiment period of 50 days. The results were as follows： 1） The intakes of dry matter， crude protein， neutral and acidic detergent fibers in the OC group were significantly higher than the OH group （P≤0.05）. 2） There were no significant differences in rumen pH， total volatile fatty acid， acetic acid and propionic acid contents； nor in the ratio of acetic acid to propionic acid and ammonia nitrogen concentration between the two groups （P>0.05）. 3） There was no significant difference in the OTU number and Chao1 index of rumen bacteria between the two groups （P>0.05）， but the Shannon index and Simpson index of rumen bacteria were significantly higher in the OC group than in the OH group （P≤0.05）. 4） Bacteroidetes and Firmicutes were the dominant phyla of rumen bacteria in both treatment groups. However， the relative abundances of unidentified-bacteria， Verrucomicobacteria， Planctomycetes， Kiritimaitiellaeota， Acidobacteria， Chloroflexi， Lentiphaerae， and Actinobacteria in the OC group were significantly higher than in the OH group （P≤0.05）. The relative abundance of Bacteroidetes tended to be significantly increased （P=0.075） and the relative abundance of Fibrobacteres tended to be significantly reduced in the OC group （P=0.096）. At the genus level for the OC group， there was a tendency to have significantly increased relative abundance （P=0.071） of unidentified taxa from the phylum Lentiphaerae and to have significantly decreased Fibrobacter relative abundance （P=0.069）； at the species level， compared with the OH group， the relative abundance of Prevotella_sp._1c2012 in the OC group showed an significantly increasing trend （P=0.065）. 5） The total volatile fatty acids were significantly positively correlated with the relative abundance of the unidentified-bacteria species （r=0.660， P=0.027） and Bacterium_P3 （r=0.638， P=0.035）. There was a significant positive correlation between acetic acid and the relative abundance of unnamed Prevotellaceae （r=0.627， P=0.039） and Prevotellaceae_bacterium_MN60 （r=0.752， P=0.008）， but acetic acid was significantly negatively correlated with the relative abundance of Bacterium_P3 （r=-0.642， P=0.033）. Propionic acid was significantly positively correlated with the relative abundance of Bacterium_P3 （r=0.647， P=0.031）， acetic acid∶propionic acid was significantly positively correlated with the relative abundance of Prevotellaceae_bacterium_MN60 （r=0.699， P=0.017）； and the concentration of ammonia nitrogen was significantly negatively correlated with the relative abundance of Alistipes （r=-0.752， P=0.008）. In summary， feeding oat cubes had no adverse effect on rumen fermentation of sheep， and increased the diversity of rumen microbiota and the relative abundance of beneficial bacteria， optimized rumen microbial composition. These results are applicable to both sheep and cattle rearing.

Key words: oat, hay, cube, sheep, fermentation parameter, rumen microorganism