Investigating Maternal Residual Feed Intake and Diet Interactions on Myogenic Gene Expression in Newborn Calves

Maternal nutrition during gestation affects metabolism and muscle development in offspring, while selection for residual feed intake (RFI) may alter an animal’s metabolism and energy partitioning. The effect and the interaction between RFI and maternal nutrition during gestation, on expression of members of the IGF and myogenesis gene families, were investigated in offspring of purebred Angus heifers selected and bred for divergent potential of RFI. High and low RFI (HRFI, LRFI) bred heifers (n=62) were assigned randomly, but in equal numbers to a low diet (Ldiet; formulated for 0.5 kg/d ADG), or a high diet (Hdiet; formulated for 0.7 kg/d ADG) from 30 to 150 days of gestation, after which all heifers consumed the same diet until the end of gestation. Within a week after birth, longissimus dorsi muscle biopsies were harvested from calves (Hdiet-HRFI [HH]=15, Hdiet-LRFI [HL]=14, Ldiet-HRFI [LH]=13, and Ldiet-LRFI [LL]=9), and real-time PCR was used to measure gene expression. MYF6 was increased in LRFI calves compared to HRFI calves (P <0.05), while IGF2R tended to be decreased in LRFI calves compared to HRFI calves (P< 0.1). Maternal diet did not have a significant effect. However, diet by RFI interactions were observed in IGF2 expression; LH had lower expression compared to HH and higher expression than LL (P<0.05). These results indicate that RFI, and pre-natal maternal diet influenced the expression of important growth and myogenesis genes, which could impact muscle development and effect economic traits such as meat production and quality.