Maternal protein supplementation during mid-gestation improves offspring performance and metabolism in beef cows.

This study examined the impact of maternal protein supplementation during mid-gestation on offspring, considering potential sex-related effects. Forty-three pregnant purebred Tabapuã beef cows (20 female; 23 male fetuses) were collectively managed in a pasture until 100 days of gestation. From 100 to 200 days of gestation, they were randomly assigned to the Restricted group [(RES) - basal diet (75% corn silage + 25% sugar cane bagasse + mineral mixture); n = 24] or Control group [(CON) - same basal diet + based-plant supplement [40% of crude protein, 3.5 g/kg of body weight (BW); n = 19]. From 200 days of gestation until parturition, all cows were equally fed corn silage and mineral mixture. During the cow-calf phase, cows and their calves were maintained in a pasture area. After weaning, calves were individually housed and evaluated during the backgrounding (255-320 days), growing 1 (321-381 days), and growing 2 (382-445 days) phases. Offspring's blood samples were collected at 210 and 445 days of age. Samples of skeletal muscle tissue were collected through biopsies at 7, 30, and 445 days of age. Muscle tissue samples were subjected to reverse-transcription quantitative polymerase chain reaction analysis. Prenatal treatment and offspring's sex (when pertinent) were considered as fixed effects. The significance level was set at 5%. At mid-gestation, cows supplemented with protein reached 98% and 92% of their protein and energy requirements, while non-supplemented cows attained only 30% and 50% of these requirements, respectively. The RES offspring were lighter at birth (27 kg vs. 31 kg), weaning (197 kg vs. 214 kg), and 445 days of age (398 kg vs. 429 kg) (P ≤ 0.05). The CON calves had greater (P < 0.05) morphometric measurements overall. The CON offspring had ~26% greater muscle fiber area (P ≤ 0.01). There was a trend (P = 0.06) for a greater Mechanistic target of rapamycin kinase mRNA expression in the Longissimus thoracis in the CON group at 7 days of age. The Myogenic differentiation 1 expression was greater (P = 0.02) in RES-females. Up-regulation of Carnitine palmitoyltransferase 2 was observed in RES offspring at 445 days (P = 0.04). Expression of Fatty acid binding protein 4 (P < 0.001), Peroxisome proliferator-activated receptor gamma (P < 0.001), and Stearoyl-Coenzyme A desaturase (P < 0.001) was upregulated in CON females. Therefore, protein supplementation during gestation enhances offspring growth and promotes favorable responses to lipogenesis, particularly in females.