Regulation effect of grape pomace on rumen fermentation and microflora of fattening sheep

Grape pomace is a by-product of wine production. The effect of grape pomace on rumen microflora and fermentation parameters is worth investigating because it could be a potential feed source for ruminants, and the reuse of waste resources in wine industry could be improved. Eighteen male Dorper (♂) × Small-tail Han sheep (♀) F₁ lambs (90～105 d of age) were randomly assigned to two diet groups: A control diet (CON, n = 9) and a diet containing 16% grape pomace (GP, n = 9). All the lambs were sacrificed after a 70-day fattening period. The pH, volatile fatty acid concentrations, and nitrogen metabolism parameters of rumen fluid were measured. Ruminal bacterial diversity was determined via high-throughput sequencing of 16S rDNA. The results showed that the rumen pH and total nitrogen concentration were higher in the GP than in the CON (P < 0.1), whereas the isobutyrate and NH₃-N concentrations were significantly lower in the GP than in the CON (P < 0.05). The relative abundance of Fusobacteria and Synergistetes were significantly higher in the GP group than in the CON (P < 0.05). Among the 16 genera with > 0.1% relative abundance, Veillonella and Selenomonas were significantly lower in the GP (P < 0.05) than in the CON. However, alpha and beta diversity analyses showed that grape pomace did not significantly affect ruminal microbial diversity. In conclusion, the diet with the inclusion of 16% grape pomace inhibited rumen protein degradation and decreased the abundance of lactic acid decomposition bacteria in fattening sheep; however, it did not affect rumen microbial diversity and rumen carbohydrate metabolism.