Effects of various weaning times on growth performance, rumen fermentation and microbial population of yellow cattle calves.

OBJECTIVE: This study was conducted to investigate the effects of weaning times on the growth performance, rumen fermentation and microbial communities of yellow cattle calves. METHODS: Eighteen calves were assigned to a conventional management group that was normally weaned (NW, n = 3) or to early weaned (EW) group where calves were weaned when the feed intake of solid feed (starter) reached 500 g (EW(500), n = 5), 750 g (EW(750), n = 5), or 1,000 g (EW(1,000), n = 5). RESULTS: Compared with NW, the EW treatments increased average daily gain (p<0.05). The calves in EW(750) had a higher (p<0.05) starter intake than those in EW(1,000) from wk 9 to the end of the trial. The concentrations of total volatile fatty acids in EW(750) were greater than in NW and EW(1,000) (p<0.05). The EW treatments decreased the percentage of acetate (p<0.05). The endogenous enzyme activities of the rumen were increased by EW (p<0.05). EW had no effect on the number of total bacteria (p>0.05), but changes in bacterial composition were found. CONCLUSION: From the present study, it is inferred that EW is beneficial for rumen fermentation, and weaning when the feed intake of the starter reached 750 g showed much better results.