Supplementing pregnant Merino ewes with caffeine to improve neonatal lamb thermoregulation and viability.

Percentages of lamb mortalities prior to weaning are a significant and persistent problem for the Australian sheep industry. Maternal caffeine supplementation reduced stillbirths and improved viability in piglets; however, the efficacy of caffeine in enhancing viability and lamb survival is equivocal. The aim of this study was to determine the optimal concentration and duration of maternal caffeine supplementation to improve lamb viability; time to stand and suck with consumption of colostrum occurring, as well as survival to weaning. Multiparous Merino ewes were supplemented with either 0 (CTL), 10 (C10) or 20 mg/kg (C20) body weight (BW) caffeine in feed after day 120 of gestation (dG), or 20 mg/kg BW (LC20) caffeine from dG 142 until parturition. Ewes were housed indoors in individual lambing pens from dG 130 to 72 -h post-partum (pp). Values for pp ewe and lamb variables were analysed using a generalised linear mixed model in IBM SPSS version 25. While ewes within the CTL, C10 and LC20 groups consumed more caffeine compared to C20 ewes (P =  0.001), lambs of C20 ewes had greater rectal temperatures at 20 -h pp (P =  0.021), greater 4 -h serum IgG concentrations (P =  0.041), a longer latency to first sucking bout (P =  0.030), and a greater number of sucking attempts (P =  0.044) compared to lambs from CTL, C10 and LC20 ewes. These results indicate that caffeine supplementation during late-gestation stimulates neonatal lambs as a result of increased sucking (4 -h serum IgG) and increased temperatures within the first 24 -h.