Pair housing presents an alternative to individual or larger group housing systems, though the effects of different pairing ages on calf welfare are not well understood. In this study, we examined the impact of pairing age on the performance, health, and behavior of dairy calves. A total of 140 Holstein female calves (n = 70 pairs) were used, paired at 3 ages: Early (6-7 d; 48 calves), Intermediate (29-30 d; 48 calves), and Late pairing (49-50 d; 44 calves). Calves were housed individually before pairing and weaned at 78 ± 2 d of age. Weight measurements were recorded at birth, 30, 50, 60 d, and at weaning. Calves' behavior was assessed 5 times per week through scan sampling after milk feedings from d 6-7 until weaning, and a food neophobia test was conducted at 50-51 d. Health assessments were performed 3 times per week by a veterinarian using Wisconsin clinical scores to diagnose diarrhea and BRD, with pulmonary ultrasonography at 55 d. The results suggest no association between pairing age and the prevalence of diarrhea or bovine respiratory disease (BRD), although our statistical power was limited. The number of calves with lung consolidation scores above 2 was also unaffected by pairing age. Early paired calves exhibited more exploration and play behaviors, and less idleness, stereotypies, and non-nutritive oral behaviors than Late paired calves. No differences were observed in cross-suckling likelihood across pairing ages. Early paired calves also showed a shorter latency to touch a novel feed in the food neophobia test, higher calf starter intake during the first 15 d, and greater ADG up to 50 d. Although overall ADG did not differ among pairing ages, Early paired calves were more homogeneous in weaning weight compared with Late paired calves. In conclusion, early pairing supports calves' initial development, promoting early feeding behavior and growth, enhancing behaviors associated with positive affective states, and without adverse effects on health or undesirable behaviors.
Keywords: Exploration; cross-suckling; disease; food neophobia.
The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).