Influence of post-calving regrouping strategy on welfare and performance parameters in dairy heifers

Thirty-six Holstein Friesian heifers (dairy herd replacements) were assigned to one of three regrouping treatments during the post-calving period. In Treatment 1, heifers were introduced individually to an established group of cows and heifers within 24 h of calving (‘Single—day 1’). In Treatment 2, heifers were housed individually in a straw pen for 1 week after calving before being added individually to the group (‘Single—day 7’). In Treatment 3, two heifers were housed together in a straw pen for 1 week after calving before being added as a pair to the group (‘Pair—day 7’). The size of the resident group remained constant at 16 animals (10 mature cows and 6 first-lactation heifers). The behaviour of the heifers was assessed during their first 8 h and first month in the resident group, and milk yield parameters, body condition loss and live weight loss were assessed during the first month post-calving. Reproductive performance was assessed during the post-calving period, and hoof health parameters were measured 1 month prior to calving, and at 1 and 3 months post-calving. Heifers in the ‘Pair—day 7’ treatment appeared to associate closely during their first month in the group by spending more time than expected in the same pen area and in adjacent cubicles (P < 0.001). During the first 8 h in the group, heifers in the ‘Pair—day 7’ treatment tended to lie down more (when more than half of the resident group was lying) than heifers in other treatments (P < 0.06). However, during the first month in the group heifers in the ‘Pair—day 7’ treatment appeared more active than heifers in other treatments (P < 0.05), and it is suggested that this reflected reduced fearfulness. Heifers in the ‘Pair—day 7’ treatment also tended to show greater milk protein yields and milk fat + protein yields during the first month post-calving than heifers in other treatments (P < 0.1). Heifers in the ‘Pair—day 7’ treatment showed greater hoof lesion scores at 3 months post-calving than heifers in other treatments (P < 0.01), and it is suggested that this reflects greater levels of behavioural activity during the first month post-calving. There were no significant differences in behavioural and performance parameters between heifers in the ‘Single—day 1’ and ‘Single—day 7’ treatments. Reproductive performance, and post-calving live weight and body condition losses were not affected by any of the treatments in this study.