PS13-25. Effects of Feeding Level on Pregnancy Performance, Metabolic Responses, and Reproductive Efficiency in Primiparous Ewes and Their Offspring.

Abstract Maternal nutrition is a key determinant of metabolic regulation, fetal development, and reproductive efficiency in sheep. This study evaluated how three gestational feeding levels 80%, 90%, and 100% of Ad Libitum intake affect pregnancy performance, maternal metabolic responses, and early offspring growth in primiparous Katahdin × Dorper ewes. Thirty-six ewes were individually housed and fed a foragefree diet formulated with alfalfa meal, DDGS, soybean hulls, molasses, poultry fat, and monocalcium phosphate to achieve 18% crude protein, 3.0 Mcal DE/kg, and a Ca:P ratio of 2.1. Blood samples collected pre-gestation, during gestation, and postpartum were analyzed for NEFA, glucose, BUN, oxidative stress markers, and metabolic hormones including leptin, ghrelin, estradiol, and cortisol. Off-spring were evaluated at birth and weighed weekly through 35 days, with weaning weights assessed at the end of the growth period. Feed intake differed significantly among treatments (P < 0.001), confirming successful establishment of three distinct nutritional planes. NEFA concentrations varied across physiological stages, with postpartum values significantly higher than all other timepoints, reflecting increased mobilization of body fat during parturition and early lactation. However, feeding level did not significantly alter NEFA concentrations, indicating that moderate restriction or slight overfeeding did not disrupt circulating fatty acid levels. Birth weight was significantly affected by treatment (P < 0.005) and time (P < 0.001). Lambs from the 80% and 100% groups were heavier at birth than those from the 90% group, demonstrating a nonlinear response to maternal intake. This same pattern persisted through weaning: lambs from the 80% and 100% groups maintained higher weaning weights compared with lambs from the 90% group, indicating that maternal feeding level influenced both initial and later early-life growth outcomes. Despite these differences in birth and weaning weights, average daily gain through week 5 did not differ among treatments, suggesting that early postnatal growth rate was resilient to maternal nutritional plane. Weekly live weights increased over time (P < 0.001), consistent with normal growth trajectories. Overall, results indicate that gestational feeding level influences both birth and weaning weights but does not significantly alter NEFA concentrations or early postnatal growth rate. Elevated postpartum NEFA confirms increased metabolic demand during parturition and lactation. The finding that both restricted (80% ad libitum) and high (100% ad libitum) intake produced heavier lambs at birth than the moderate (90% ad libitum) group highlights the relationship between maternal intake and offspring growth. These findings underscore the complexity of metabolic-nutritional interactions during gestation and provide practical insight for refining feeding strategies to improve reproductive efficiency and flock productivity in hair sheep systems.