Chengquan Han

Lambs are typically weaned at 3–5 months of age, while early weaning (e.g., at one month of age) can readily induce ewe-lamb separation stress. Although improvements in weaning methods have shown some effectiveness in alleviating stress associated with early weaning, previous studies have mainly focused on stress responses in lambs, with relatively little attention given to ewes. Stress training is a method in which animals are exposed to specific stressors in advance to reduce their sensitivity to subsequent stimuli. This study aimed to investigate whether 1 h of pre-weaning ewe-lamb separation stress training (PWLSST) applied to ewes scheduled for early weaning (Day 35) could reduce post-weaning stress responses, improve behavioral performance, and explore the underlying mechanisms. The results showed that, compared with normally weaned ewes, ewes in the PWLSST group exhibited significantly reduced vigilant watching behavior and markedly increased relaxation-type behaviors (lying, exploring after weaning (P < 0.05). Concurrently, catecholamine (CA) levels in the PWLSST group were significantly decreased (P < 0.05). In summary, 1 h of PWLSST significantly reduced vigilant behavior and increased the proportion of relaxed behaviors in early-weaned ewes, which may indicate a marked reduction in stress levels. These improvements may be associated with decreased CA levels, which are related to chronic stress responses. These findings suggest that appropriate ewe-lamb separation stress training before weaning can help alleviate stress responses in early-weaned ewes, improve behavioral performance, and thereby enhance ewe welfare. This study provides a valuable reference for developing appropriate early-weaning protocols in meat sheep production.

Context: Different individuals within a group can form strong links through auditory, visual, and tactile senses. Temporarily separating sheep into subflocks, although not involving complete social isolation of individuals, can be stressful, especially when ewes are separated from lambs. Aims: This study aimed to explore the effects of 1-h temporary ewe–lamb sensory separations on stress-related behaviours during separation, as well as its effect on stress-related hormones of ewes. Methods: Small-tailed Han ewes were randomly assigned to the following four groups (six each): the auditory + visual + tactile separation (A + V + T group), visual + tactile separation (V + T group), tactile separation (T group), and the control (C group). Then, the ewes were separated from their lambs for 1 h on Postnatal Days 14, 21, 28, 35 and 42. Ewe behaviours during the separations were observed using focal animal-sampling methods. Key results: Results showed that the separated ewes (A + V + T, V + T, and T groups) spent more time looking and exploring and less time lying (P < 0.05). Ewes showed more exploring behaviour in T group (P < 0.05). Ewes that gave birth to two lambs showed more urinating behaviour (P < 0.05). There was no significant difference in the level of stress-related hormones in ewes among the four different separation-method groups (A + V + T, V + T, T, and C groups). Conclusions: One hour ewe-lamb sensory separation affected the stress related behaviours of Small-tailed Han ewes during separation, but it did not cause differences in stress-related hormones in ewes after the separation. Ewes showed increased exploring or urinating behaviour when they were separated through lack of tactile contact only with lambs, or when ewes give birth to two lambs. Implications: Ewes temporarily separated from their lambs are less stressed if they are unable to hear or see the lambs, thereby improving ewe welfare. These effects appear more pronounced in ewes with multiple lambs and provides new perspectives for further studies on the effect of litter size on ewe-lamb bonding.