Maternal undernutrition affects secondary myogenesis in a muscle-dependent way across the major muscles of 70-day old ovine fetuses

Abstract The present study evaluated the effects of maternal undernutrition induced by a lower natural pasture allowance from 23 days before conception on the distribution and morphometry of muscle precursor cells and the expression of PCNA, Myogenin and Pax 7 in muscles Psoas major, Longissimus lumborum, Semitendinosus, Semimembranosus, Gluteobiceps and Gluteus medius of 70-day old sheep fetuses. Ewes were assigned to two nutritional treatments (complete randomized block design) beginning 23 days before conception: High pasture allowance (HPA) ewes grazed on natural grasslands at 10-12 kg dry matter (DM) /100 kg of live weight (LW)/day, while low pasture allowance (LPA) ewes grazed at 5-8 kg DM /100 kg of LW/day. On day 70 of pregnancy 18 ewes (nine/treatment) carrying single male fetuses were euthanized and samples were taken from fetal muscles. Samples were stained with hematoxylin-eosin to evaluate muscle morphology and treated with immunohistochemical methods to evaluate the expression of myogenic regulatory factors. Maternal undernutrition reduced the ratio of secondary to primary fibers (P