Effect of early rearing experience on subsequent behavior and production of Holstein heifers

Sixty-seven heifer calves were assigned at birth to one of four rearing treatments: groups of six, individual hutch, isolation, and isolation with handling (10 min daily interaction with calf feeder). Calves were on the same diet and except for group calves were in 1.2 X 2.4-m hutches. Group calves were in open shed housing with 3m2/calf. Calves were weaned at approximately 10 wk and then assimilated into regular herd routine. An open field test of 3 min for each calf was conducted on 3 consecutive days at weaning. Samples for blood plasma glucocorticoids were taken before and after open field testing. Forty-eight heifers milked twice daily completed 305-day lactations. There were no differences in weaning weight or average daily gain to weaning. Group calves urinated and defecated more during open field tests, but number of vocalizations was not different. There was a significant rise of glucocorticoids for all calves, but treatment effects were nil. Cows reared in isolation (treatments 3 and 4) produced significantly more milk (922 kg 3.5% fat-corrected milk), had a 1205 kg advantage in relative milk, but were not different from group or individually reared cows in relative milk fat. A hypothesis to explain these results is proposed.