Effect of gestational naural pasture allowance on muscle development of lambs

Abstract

To study the effects of gestational undernutrition induced by a lower natural pasture allowance on myogenesis and meat production in lambs, two experiments were carried out. In the first, Corriedale sheep were fed contrasting natural pasture allowances (23 days before conception until gestation day 122) and myogenesis was evaluated in 70-day-old fetuses and newborns. In the second, similar ewes were fed with contrasting natural pasture allowances (day 30 of gestation until parturition) and the productive performance, quantity and quality of meat and muscular characteristics in 200-day-old lambs were evaluated. A lower pasture allownace affected fetal myogenesis (fewer secondary fibers) and was associated with reduced mitotic and myoblastic fusion activity in some muscles. In newborns, maternal undernutrition affected muscle histology, fibrillar biological and contractile properties (MyHC-I and GLUT-4). Likewise, undernutrition strongly reduced muscle IGF-1 and could compromise neonatal hypertrophic compensation. On the other hand, maternal undernutrition from day 30 to parturition affected growth, carcass quality and muscle weights at 200 days, although these effects were mainly sex-dependent, with males being the most affected. Maternal undernutrition affected fibrillar composition (greater oxidative activity) in all muscles at 200 days. Biochemical and meat quality characteristics were also affected, although these effects depended on both muscle and sex. In summary, a lower gestational pasture allowance negatively affected fetal myogenesis and neonatal muscle characteristics (worse hypertrophic capacities), and induced fetal programming effects on muscle mass and muscle characteristics at 200 days. This implies that, regardless of postnatal conditions, intrauterine alterations induce muscular changes, which may be related to the ability to grow and the quality of the meat produced. Likewise, our results highlight the importance of considering the sex of the animal and the muscle when studying these effects.