PSVII-12 - The effects of parity and diet on the rumen function and apparent digestibility in dairy cattle

The primiparity and multiparity dairy cattle were fed in the same diet and different barn in the scaled farm because heifer has a lower social hierarchy. There is little attention to the rumen function difference of these cattle. Here we selected thirty-two dairy cattle and separated them into four groups: prime-prepartum (PP), prime-lactation (PL), multi-prepartum (MP), and multi-lactation (ML) (n=8). The PP and MP groups were given high-roughage diets, and the other two groups were given high-grain diets. The rumen fluid and feces were sampled from each animal. The rumen fluid enzyme activity, fermentation profile, and apparent digestibility were analyzed using SAS's PROC MIXED model (SAS version 9.4, SAS Institute Inc., Cary, NC, USA). β-glucosidase and amylase were affected by the parity and diet (P < 0.05). Cellulase was affected by the parity, and dehydrogenase was affected by parity and diet interaction (P < 0.05). Rumen pH, NH₃-N, microbial crude protein (MCP), isovalerate, and acetate/propionate (A/P) were affected by parity (P < 0.05). MCP and volatile fatty acid were affected by the diets (P < 0.05). The rumen pH, acetate, propionate, and butyrate were affected by parity and diet interaction (P < 0.05). The apparent digestibility of the neutral detergent fiber, acid detergent fiber, crude protein (CP), and ether extract (EE) were affected by the diet and the interaction of diet and parity (P < 0.05). The CP and EE apparent digestibility were only affected by the parity (P < 0.05). Our results indicated beside the diet, the parity also affected the rumen function and apparent digestibility. Although the dairy cattle in the same physical stage, the parity effects on the rumen function and digestibility should be considered when making the diet formula.