Prenatal stress improves the ability of neonatal lambs to maintain body surface temperature during periods of cold exposure.

Exposure to cold and hypothermia is a significant threat to newborn lamb survival in extensive systems, and the ability to thermoregulate is essential for improved survivability. Lambs exhibit enhanced thermogenic abilities and increased brown fat deposition when ewes experience cold during late-pregnancy. This study evaluated the effects of various prenatal stressors on newborn lamb thermogenesis through three experiments. Experiment 1 examined the impact of mid-pregnancy shearing and wetting on lamb thermogenesis. Experiment 2 involved transporting and cold-exposing late-pregnancy ewes. Experiment 3 combined stressors like yarding, transport, wetting, and cold exposure in mid- or late-pregnancy ewes. Four-hour-old lambs were subjected to a 1-hour cold challenge during which infrared thermal images from the dorsal midline were taken every 10 min. Lambs from ewes shorn and wetted during mid-pregnancy tended to have higher body surface temperatures than those handled during mid-pregnancy (Experiment 1; P = 0.073) and they also maintained body surface temperature better during the cold challenge (Experiment 1; P = 0.025). Lambs from ewes exposed to late-pregnancy combined stressors showed higher radiated body surface temperatures than both mid-pregnancy stressed and control lambs (Experiment 3; P < 0.05) while late-pregnancy stress group lambs maintained radiated body surface temperature longer than both mid-pregnancy stressed and control groups lambs (Experiment 3; P < 0.01). The study concludes that cold exposure combined with husbandry stressors leads to differences in lamb thermogenesis, with mechanisms varying based on the timing of stressors.