The effect of weaning age on performance and economics of Holstein calves reared under organic farming system.

The objective of this study was to evaluate the effects of weaning age on dry matter intake (DMI), average daily gain (ADG), feed efficiency (FE), feed cost (FC) and benefit index (BI) of Holstein calves reared under organic farming system. Thirty two Holstein calves were divided into two treatments: early weaning (EW) vs. late weaning (LW). Calves in the both groups were provided with whole milk at the rate of 10% body weight (BW). Calves had free access to leafy alfalfa hay from birth until the end of the experiment. Also, the EW group was provided with starter diet after weaning till 90 days of age. The daily DMI and BW at 15-day intervals were measured and FE and FC were calculated for periods. The DMI of LW and EW calves was significantly different from third period to end of experiment. Moreover, ADG of EW was higher than LW in all of periods. Except for first and second, FE was significantly different between the groups in other periods. Also, due to an increase FC for calves reared on LW compared to EW-calves group, the BI was higher in EW-calves.