Effects of milk replacer and whole milk feeding on rumen development, expression of genes related to volatile fatty acid absorption, and rumen bacteria in calves

This research examined the effects of liquid feeds on calf performance, rumen development, rumen cellulolytic bacteria count, and total bacteria diversity. Twenty Holstein bull calves were allocated to 2 groups either fed with milk replacer (MR) or whole milk. Calves fed milk tended to have higher (P = 0.058) average daily weight gain as compared to calves fed with MR during the entire experimental period. Starter mixture intake was not influenced by either milk or milk replacer feeding. Calves fed with milk had higher (P < 0.001) proliferative cells in the rumen papilla. The expressions of MCT1, MCT4, NHE1, NHE3, ACSS1, AceCS2, and ACSM1 genes, which are related to volatile fatty acid absorption, in the dorsal sac of the rumen were similar for calves fed either MR or whole milk. Fibrobacter succinogenes (P = 0.017) and Ruminococcus flavefaciens (P = 0.037) were significantly higher in the rumen of the milkfed calves. Moreover, denaturing gradient gel electrophoresis (DGGE)-derived dendrograms showed noticeable differences in ruminal microbial population between MR-fed and milk-fed calves. In conclusion, feeding calves with whole milk, which contains better quality protein and nutrients, instead of milk replacers, positively affects rumen development, cellulolytic bacteria numbers and total bacteria diversity.