EFFECTS OF ISOLATION OF CALVES ON GROWTH, BEHAVIOR, AND 1ST LACTATION MILK-YIELD OF HOLSTEIN COWS

Holstein (n = 323) calves in the herds of four experiment stations were reared individually (control) or in isolation to 70 d of age to determine whether isolation affected growth, behavior, and first lactation yield. Treatment differences were not observed for average daily gain for BW at d 28, 56, or 70. Postweaning approach distance was measured in two herds (n = 122; n = 28). Detailed pre- and postweaning behaviors were reported in one herd (n = 26). Isolation did not affect subsequent milk yield or culling percentages. In a second experiment, seven pairs of monozygous twins and a set of identical triplet calves were obtained by transferring split embryos into recipients, one member of each pair was reared in a group, and the twin was reared in isolation. Early rearing previously had been found to affect growth, feed intake, dominance rank, and learning ability of calves, and, in our study, the subsequent milk yield of calves reared in isolation tended to average more than for calves in groups. Intraclass correlations between monozygous twin pairs for milk, fat, relative value milk, and relative value fat were lower than anticipated. These data indicate that preweaning isolation did not affect first lactation milk yield traits.