RESUMO: O objetivo deste estudo foi avaliar o efeito da suplementação proteica materna sobre o metabolismo energético do músculo esquelético de bezerros de corte. Dezesseis matrizes gestantes foram divididas em três grupos: CONTROLE (não suplementado); MÉDIO (suplementados entre 30 e 180 dias de gestação); e FINAL (suplementado entre 181 e 281 dias de gestação). O suplemento continha 30% de proteína bruta e foi fornecido em quantidades totais iguais aos tratamentos. Trinta dias após o nascimento, amostras de sangue e músculo dos bezerros foram coletadas para análises de expressão gênica, abundância de proteínas e metabólitos. Não foram observadas diferenças (P ≥ 0,15) no peso ao nascimento ou parâmetros de desempenho ao desmame, bem como na expressão dos genes avaliados (P ≥ 0,21). Os bezerros nascidos de matrizes do tratamento CONTROLE apresentaram menor proporção (P = 0,03) de proteína p-AMPK/AMPK no músculo esquelético. Os bezerros nascidos de matrizes do tratamento MÉDIO apresentaram concentração de glicose menor (P = 0,04) do que aqueles nascidos de matrizes do tratamento FINAL. Os resultados observados indicam que a ausência de suplementação proteica em matrizes gestantes pode alterar o metabolismo energético da progênie e refletir em uma inflexibilidade metabólica, a qual pode ocasionar limitações quanto à eficiência energética do tecido muscular esquelético e consequentemente, limitar o desempenho da progênie ao longo da fase pós-natal.

ABSTRACT: This study evaluated the effect of maternal protein supplementation during mid or late gestation on energy metabolism of the skeletal muscle of beef calves. Sixteen pregnant cows were divided into 3 groups: CTRL (not supplemented); MID (supplemented from 30 to 180 days of gestation); and LATE (supplemented from 181 to 281 days of gestation). The supplement contained 30% crude protein. Thirty days after birth, blood and muscle samples of the calves were collected for analyses of gene expression, proteins, and metabolites. No differences (P ≥ 0.15) in birth weight, performance at weaning, or muscle expression of the genes evaluated (P ≥ 0.21) were observed. Calves born to CTRL cows had a lower ratio (P = 0.03) of p-AMPK/AMPK protein in the skeletal muscle. Calves born to MID cows had lower (P = 0.04) glucose concentration than those born to LATE cows. Changes in p-AMPK/AMPK protein, indicated a possible metabolic inflexibility in the skeletal muscle of calves born to CTRL cows. These results indicated that lack of protein supplementation in pregnant cows alter the energy metabolism of their calves and reflect in a metabolic inflexibility.

ABSTRACT This study evaluated how nutritional insults applied at different stages of intrauterine development affect the growth and development of total tract organs and the mRNA expression of genes that encode growth factors, tight junction proteins, digestive enzymes, and glucose transporters in the small intestine of newborn goats. Fourteen nulliparous dairy goats were assigned to one of two nutritional plans over gestation: maintenance-restriction (M-R, n = 8) – 100% of maintenance requirement from d 8-84 of gestation followed by feeding at 50% maintenance requirement from d 85 of gestation to parturition; or restriction-maintenance (R-M, n = 6) – 50% of maintenance requirement from d 8-84 of gestation followed by feeding at 100% maintenance requirement from d 85 of gestation to parturition. Fisher's least significant difference test was performed using SAS 9.4, considering a full fixed-effect model. When expressed per kg of body weight, the weights of the small intestine and total intestine were 18.7 and 18.1% lower, respectively, for R-M offspring. The lengths of the small intestine and the total intestine of the R-M newborns were 19.1 and 9.5% shorter, respectively. This group also had a lower villus height:intestinal crypt depth ratio. The R-M offspring tended to have lower Solute carrier family 5 member 1 (SLC5A1), Solute carrier family 2 member 2 (SLC2A2), and Occludin (OCLN) mRNA expressions. Therefore, feed restriction in the first half of gestation is detrimental to the second half of gestation, reducing the offspring's intestinal absorptive area but enhancing their intestinal permeability.

ABSTRACT The productive traits of beef cattle are orchestrated by their genetics, post-natal environmental conditions, and also by the intrauterine background. Both under- or overnutrition, as specific dietary components, are able to promote persistent effects on the offspring. This occurs because dietary factors act not only affecting the availability of substrates for fetal anabolism and oxidative metabolism, but also as signals that regulate several events toward fetal development. Therefore, this study aimed to summarize the gestational nutrition effects on the offspring performance and meat quality in a long term. Overall, studies have shown that many of these alterations are under the control of epigenetic mechanisms, as DNA methylation, histones modification, and non-coding RNA. The current knowledge has indicated that the fetal programming responses are dependent on the window of fetal development in which the dietary treatment is applied, the intensity of maternal nutritional stimuli, and the treatment application length. Collectively, studies demonstrated that muscle cell hyperplasia is impaired when maternal requirements were not achieved in the second third of gestation, which limits the formation of a greater number of muscle fibers and the offspring growth potential in a long term. Changes in muscle fibers metabolism and in collagen content were also reported as consequence of a dietary perturbation during pregnancy. In contrast, a maternal overnutrition during the late pregnancy has been associated with beneficial responses on meat quality. In summary, ensuring an adequate maternal environment during the fetal development is crucial to enhance the productive responses in beef cattle operations.