Maternal metabolizable energy intake during late gestation affects energy metabolism of the skeletal muscle of beef offspring.

The objective of this study was to evaluate the effects of varying levels of maternal metabolizable energy (ME) intake during late gestation on the changes in postnatal development of skeletal muscle in calves. A total of 42 primiparous (n†=†21) and multiparous (n†=†21) pregnant Angus-Simmental beef cows (680.8†±†74.4 kg) were housed indoors at the Ontario Beef Research Center at the University of Guelph. Cows were blocked by predicted calving date, balanced by initial body weight and parity, and randomly assigned to one of 3 treatment diets designed to provide 92% (LME, n†=†16), 104% (CME, n†=†13), or 118% (HME, n†=†13) of predicted ME requirements, based on a 715 kg Angus cow with body condition score (BCS) 7 programmed to lose 2 BCS units over late gestation. All cows were managed under a planned moderate negative energy balance starting 53 d before expected calving. At birth, calves were weighed before suckling the dam, and again on day 209 at weaning. At 28 d of age, plasma and serum samples were collected for insulin, glucose, BHBA, and non-esterified fatty acids analysis. At 30 d of age Longissimus muscle samples were biopsied from the calves and were used for mRNA expression and protein abundance for energy metabolism. All statistical analyses were performed in SAS Studio, in a mixed model including the fixed effects of treatment and parity, and the random effect of sire. No differences were observed among treatments for calf birth weight, weaning weight, and metabolic profile. A lower mRNA expression of MYH1 was observed (P†=†0.02) in the skeletal muscle of calves from the HME and LME groups compared to the CME. An increased mRNA expression of both MYH2a (P†=†0.04) and MYH2†×†(P†=†0.01) was observed in calves from LME compared to HME, suggesting potential alterations in muscle fiber composition that may influence metabolic efficiency and growth performance. A greater mRNA expression of PPARα (P†=†0.04), PPARGC1α (P†=†0.04), and MEF2A (P†=†0.01) were observed in calves from the LME group compared to the HME. A greater AMPK activity was observed (P†=†0.01) in the skeletal muscle of calves from the LME group compared to CME and HME. In contrast, Akt activity was greater in HME and LME groups compared to CME (P†=†0.01). Our findings suggest that maternal ME intake affected the muscle energy metabolism of the offspring, the oxidation of fatty acids, mitochondrial biogenesis, and the use of muscle fiber-type fuel.