Mating Season Influences Placental Characteristics, Plasma IGF Concentration, and mRNA Expression without Affecting Lamb Birth Weight in Akkaraman Ewes

Seasonal variations significantly impact lambs’ birth weight and post-natal growth of lambs, yet the underlying physiological mechanisms remain insufficiently explored. Therefore, this study examined the effects of mating season on lamb birth weight, placental characteristics, maternal concentrations of insulin-like growth factors (IGFs) in plasma, and placental mRNA expression levels of IGFs in Akkaraman ewes reared under extensive conditions. Ewes were mated in the breeding season (September; n = 35) and out-of-breeding season (April; n = 27). Blood samples were taken from the jugular vein of all ewes using a vacutainer in sterile heparin tubes every month from mating to parturition. Post-lambing, both dam and lamb weights were recorded, and placental characteristics were documented within 12 hours of parturition in both seasons. The number and weight of cotyledons were higher (P