Skeletal Muscle Development in Postnatal Beef Cattle Resulting from Maternal Protein Restriction during Mid-Gestation

SIMPLE SUMMARY: The intrauterine period plays a major role in skeletal muscle development and metabolism, including the formation of muscle fibers and adipose and connective tissue. Since the embryo and fetus depend on maternal nutrition to develop and grow, understanding the effects and finding potential strategies of skeletal muscle manipulation may be a valuable alternative to enhance beef cattle performance postnatally. In the present study, we evaluated the effects of maternal protein restriction during mid-gestation on the short and long -term skeletal muscle composition of the offspring. Our results suggest that the detrimental effects of maternal protein restriction during mid-gestation were associated with decrease in muscle fibers formation and may have contributed to the increase in collagen content in the skeletal muscle of the offspring. Although the changes in muscle fiber metabolism were not persistent, maternal protein restriction may contribute to such a short-term alteration. Our findings highlight the importance of an adequate nutritional plane for pregnant beef cows, to improve offspring’s performance, and consequently, the meat quality. ABSTRACT: We aimed to investigate the effects of maternal protein restriction during mid-gestation on the skeletal muscle composition of the offspring. In the restriction treatment (RES, n = 9), cows were fed a basal diet, while in the control (CON, n = 9) group cows received the same RES diet plus the protein supplement during mid-gestation (100–200d). Samples of Longissimus dorsi muscle were collected from the offspring at 30d and 450d postnatal. Muscle fiber number was found to be decreased as a result of maternal protein restriction and persisted throughout the offspring’s life (p < 0.01). The collagen content was enhanced (p < 0.05) due to maternal protein restriction at 30d. MHC2X mRNA expression tended to be higher (p = 0.08) in RES 30d offspring, however, no difference (p > 0.05) was found among treatments at 450d. Taken together, our results suggest that maternal protein restriction during mid-gestation has major and persistent effects by reducing muscle fiber formation and may slightly increase collagen accumulation in the skeletal muscle of the offspring. Although maternal protein restriction may alter the muscle fiber metabolism by favoring the establishment of a predominant glycolytic metabolism, the postnatal environment may be a determinant factor that establishes the different proportion of muscle fiber types.