Effects of weaning and two separation strategies on cow-calf pairs kept together in an automatic milking system until calves were four months old

Sammanfattning: In the commercial dairy industry calves and cows are usually separated within 24 hours, however there is an increasing interest from the consumers to accommodate dairy cows and their calves together to improve animal welfare. Previous studies conclude that with later separation comes an increase in both calves and cows’ behavioral stress response after separation, however late separation has positive effects on the health and behavior of calves and cows. It is therefore important to minimize the stress at weaning and late separation of cow-calf pairs in the dairy industry. The aim of the study was to assess the effects of weaning calves with nose-flaps and abruptly separating (AS) or gradually separating (GS) them at approximately 4 months post-partum. The 19 cow-calf pairs were kept in a stable with an automatic milking system where cows and calves could have contact at all times. In the AS treatment, calves wore nose-flaps for 14 days before being completely separated from the cows and moved to a calf-pen. In the GS treatment, calves wore nose-flaps for 7 days and were partially separated from the cows by fence-line for an additional 7 days, before they were completely separated from the cows. On the days following weaning with nose-flaps, calves from both treatments had a significant increase in motion index, number of steps taken and standing time, and a decrease in lying time. Concentrate intake significantly increased a few days after weaning. Calves in both treatments vocalized for 4 days after weaning, however the frequency of vocalization was low and several calves from both treatments were quiet during this period. Weaning did not influence the behavior of the cows, however milk yield increased shortly after weaning. From day 0 (weaning) until day 18, calves in the GS treatment had a higher motion index (8.3 ± 0.063), number of steps taken (6.8 ± 0.072) and standing time (585 ± 11 min), and lower lying time (849 ± 10.9 min) compared to calves in the AS treatment (8 ± 0.063, 6.5 ± 0.072 steps, 561 ± 11 min and 878 ± 10.9 min respectively). On the day of complete separation (day 14) calves had an increased behavioral response, however there were no significant differences between calves in the two treatments and the vocalization response was similar. Cows in the GS treatment had an increase in motion index and number of steps, and vocalized on the day of and the day after gradual separation, as did the cows in AS treatment on the day of and the day following complete separation. Treatment had no effect on cows. In conclusion, weaning and separation of calves from their dams lead to an increased behavioral response from the calves, and abrupt separation after weaning with nose-flaps lead to a lower and more short-lived activity response from calves compared to gradual separation. Cows responded mildly to both treatments.