Temporary sensory separation of ewes from lambs effects stress-related behaviours and hormones of Small-tailed Han ewes

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.