212 Use of Vitamin A on Developmental Studies in Ruminant Animals

Abstract

Abstract Adipogenesis of intramuscular fat tissue in ruminant animals occurs from late pregnancy to first months of age. Therefore, the potential of intramuscular fat (IMF) deposition lasts from the fetal phase until weaning. This crucial period is known as the marbling window. Marbling is stablished by both hyperplasia and hypertrophy processes, and this attribute can be modulated by a strategic nutrient plan or bioactive compounds. Some studies showed that the angiogenesis process has a specific relationship, spatially and temporally, associated with adipogenesis. Adipose tissue is vastly vascularized with capillaries surrounding each adipocyte and this fact turns angiogenesis a target for manipulation, due to pericytes in the blood vessel’s cell wall differentiating into pre-adipocytes and adipocytes. Thus, the manipulation of the processes related to IMF deposition have been studied and the active form of vitamin A (retinoic acid) have been demonstrated to be a modulator of the key genes expression. However, there are still some remaining questions concerning adequate vitamin A dosage and its best administration time point. In Korean native cattle, they found that late pregnancy vitamin A supplementation increased, in the progeny, birth weight and upregulated the expression of genes related to preadipocyte and muscle development. When they supplemented vitamin A via oral to newborn calves, they observed an improvement in calf performance and upregulation in the expression of pre-adipogenic and myogenic genes. In research conducted in the United States using Angus cattle, it was found that neonatal vitamin A injections, at birth and at 30 d of age, promoted calf and muscle growth and IMF development in beef cattle. In the studies mentioned above were observed upregulation in myogenic, angiogenic and adipogenic genes, and also an increase in the pre-adipocytes formation. In our recent study in Brazil, using just one vitamin A injection at birth in crossbred beef cattle we found an increase in intramuscular fat deposition and upregulation in genes involved in angiogenesis and lipogenesis. In summary, through oral vitamin A supplementation during the gestational period or its oral supplementation or injection during the neonatal period, it is possible to upregulate expression of key genes of several biological processes (myogenesis, angiogenesis, adipogenesis and lipogenesis) and increase IMF deposition. Further research is needed to confirm if the vitamin A injection in pregnant cows results in similar or better outcomes in the progeny and the best dosages recommendations in injected or oral supplementation in newborn calves.