Effects of separation time on behavioral and physiological characteristics of Brahman cows and their calves

• We evaluated the effects of separation time on behavioral and physiological characteristics of cows and their calves.
• Stress indicators decreased as the separation period increased and calves were older.
• Cows were less affected than their young, independently of the age of the calves.

The aim of this study was to investigate the effects of separation time on behavioral and physiological characteristics of Brahman cows and their calves. Thirty Brahman cow-calf pairs raised under extensive conditions were randomly assigned to one of three temporary weaning duration: (n = 10/group): (1) 24 h, (2) 48 h, (3) 72 h. Treatment was applied at 25 and 45 days postpartum (dpp), with the same cow-calf pairs allocated to the same weaning duration treatment at both ages. Behaviors recorded include the proximity of cows and calves to the fence separating them, and animals vocalizing and/or lying down. Serum cortisol concentration in cows and calves, and calves weight loss and milk intake were calculated as physiological and productivity measures. At 25 dpp the percentage of cows at <10 m from the fence-line separating them from their calf, decreased as increasing duration of the separation period increased (Z = 6.2, p < 0.05). At 45 dpp this pattern was not observed. The number of cows vocalizing decreased as the separation period increased (37–10% and 13–0%, from 24 to 72 h at 25 and 45 dpp, respectively (Z = 6.6, p < 0.05). More calves vocalized (Z = 3.6, p < 0.05) at 24 and 48 h in comparison to 72 h, regardless of their age. In cows, increases in cortisol with respect to pre-treatment concentration were only significant (F 2/57 = 6.6 p < 0.05) when subjected to 72 h separation at 25 dpp, while in calves, increases in cortisol were inversely proportional to the duration of cow-calf separation (10.3 ± 2.9, 5.3 ± 2.2 and 2.0 ± 1.1 (F 2/57 = 6.6, p < 0.05) vs. 6.2 ± 2.8, 2.1 ± 1.4 and 0.8 ± 0.7 ng/ml (F 2/57 = 4.6, p < 0.05), at 24, 48 and 72 h of separation of 25 vs. 45 day old calves, respectively). A similar relation was observed in weight losses (5.4 ± 1.3, 2.7 ± 0.9 and 0.2 ± 0.1 (t = 8.13, p < 0.05) vs. 2.2 ± 0.9, 0.6 ± 0.5 and 0.7 ± 0.6 kg (t = 4.15, p < 0.05), at 24, 48 and 72 h of separation for 25 vs. 45 day old calves, respectively). In conclusion, most stress indicators in cows and calves decreased after 48 h of separation, cows were less affected than their young, and older calves displayed less signs of stress than younger animals.