Balancing Prolificacy and Lamb Meat Production: Links Among Litter Size, Prenatal Development, Carcass Traits, and Meat Quality in Sheep

Prolificacy can increase lamb output per ewe, but its productive value depends on the survival, growth, and carcass performance of each additional lamb. This review examines the pathway from genetic control of ovulation to realized litter size, prenatal development, neonatal viability, postnatal growth, carcass traits, and meat quality. Major fecundity genes, including BMPR1B, BMP15, GDF9, and B4GALNT2, alter ovulation rate, although evidence for direct effects of these loci on muscle development or meat quality remains scarce. Most phenotypic differences are more plausibly mediated through fetal number and the maternal environment. Compared with singletons, multiple-born lambs generally have less placental tissue per fetus, lower birth weight, reduced neonatal vigor, and slower preweaning growth. Prenatal restriction may alter myofiber formation, adipogenesis, and connective tissue development, but its later expression depends strongly on postnatal nutrition and slaughter endpoint. Across studies, litter size has a clearer and more consistent association with survival, growth trajectory, and carcass readiness than with ultimate pH, color, water-holding capacity, tenderness, intramuscular fat, fatty acid composition, or sensory quality. Reported contrasts vary with age, diet, carcass weight, and fatness; adjustment can attenuate some observed differences, but it may also remove effects mediated through growth. An effective production strategy therefore targets optimum rather than maximum prolificacy. Genetic selection should be integrated with pregnancy diagnosis, fetal-number-specific nutrition, colostrum management, rearing allocation, targeted finishing, and carcass feedback, with performance evaluated as saleable carcass output per ewe. The evidence is primarily observational for natural birth-type comparisons, while controlled nutritional models support selected prenatal mechanisms rather than equivalence to natural multiple pregnancy.