Temporary sensory separation of lamb groups from ewes affects behaviors and serum levels of stress-related indicators of small-tailed Han lambs

Abstract

Under the current meat sheep breeding system, newborn lambs usually live with their mothers until weaning, and in daily management, they often need to be separated from their ewes for a short period due to dehorning, disease treatment, etc. Such short-term separation was considered to be a high-intensity stress for the lambs. This study aimed to explore the effects of 1 h sensory separations on behaviors and the concentration of stress-related indicators of small-tailed Han lambs. Lambs were assigned to four groups: auditory, visual, and tactile separation (AVT) group; visual and tactile separation (VT) group; tactile separation (T) group; and control (C) group. Then they were separated from their mothers for one hour on postnatal days 14, 21, 28, 35 and 42. Results showed the separated lambs (AVT, VT, and T groups) spent less time lying down relaxing and more time looking around, exploring, vocalizing, and attempting to escape (P < 0.05). Lambs separated by lack of tactile contact only exhibited the most escaping and moving behavior. Twin-born lambs showed less moving, escaping, and vocalizing than single-born lambs (P < 0.05). The separation also led to a rise in serum globulin levels and a decrease in tetraiodothyronine. In conclusion, this study showed that temporary 1 h ewe-lamb separations could affect behaviors and the serum levels of stress indicators of lambs. The behavioral responses were more obvious when lambs were separated by lack of tactile contact only, and in single-born lambs. It can conclude that indicated that when lambs need to be temporarily separated from ewes in daily management production, it would be better to let them stay together with their littermates, and make them avoid hearing or seeing the ewes, such management may partially reduce the separation stress, thereby improving the welfare and breeding efficiency of sheep.