de Souza Teixeira, O., Kuczynski da Rocha, M., Mendes Paizano Alforma, A. et al. 2021. Behavioural and physiological responses of male and female beef cattle to weaning at 30, 75 or 180 days of age. Applied Animal Behaviour Science 240, 105339.

Weaning calves at a young age can generate great stress, but it is widely practiced in the industry despite that. So, to what extend weaning in early ages is more stressful than at later ones, in terms of the amount of stress, is currently unknown. Thus, we studied the behavioural and physiological impacts in beef calves at three ages at weaning (30, 75, and 180 days) and the consequences of the calf's sex. Thirty-six calves were weaned and distributed in hyper-early (W30), early (W75), and conventional (W180) weaning groups, which are weaning ages that occur in practice. Behavioural activities and physiological parameters were measured on days 0, 1, 2, and 7 after weaning. Canonical component analysis (CCA) and analysis of variance (ANOVA) were used to evaluate behavioural and physiological parameters. The variables analysed were influenced by the treatment, day of evaluation and interaction between treatment × day, and without effect for sex. The younger the calf, the greater the intensity of responses to the weaning stress. In this sense, the behavioural results (percentages of observations ± SEM) demonstrate that on D0, W30 calves emitted more extreme vocalization (61 %) compared to W75 (15 %) and W180 (0%) (P < 0.001); on D1, W30 and W75 calves expressed more extreme sounds (61 % and 50 %, respectively) than W180 (21 %) (P = 0.028). Similarly, W30 and W75 calves showed a higher number of cross-sucking (P = 0.006). On D0, differences in the frequency of walking (P < 0.001) were observed, once calves of W30 (45.5 ± 6.21 %) and W75 (39.9 ± 6.03 %) spent more time in this activity than W180 ones (17.3 ± 3.80 %). Also, more visiting the feeder without eating feed events were verified (P = 0.014) on D0 (11.5 ± 2.59 %) and D1 (6.2 ± 1.65 %) for W30 when compared to W180 calves (2.6 ± 1.73 % and 0.0 ± 0.00 %, respectively). In physiological terms, a higher respiratory rate (P = 0.043) on D0 was identified for W30 calves (66.3 ± 2.90 breaths/min) than for W75 (57.8 ± 2.30 breaths/min) or W180 (47.3 ± 2.02 breaths/min). Cortisol concentrations were higher (P = 0.019) on D0 for W30 animals (15.6 ± 3.40 ng/mL) than for W180 ones (9.7 ± 1.90 ng/mL). The peak of cortisol occurred on D1 for W30 and D2 for W75 and W180. Therefore, behavioural and physiological changes at young ages indicate greater calf suffering, which may have negative consequences on a productive life.