Effect of early-life plane of nutrition on the transcriptional profile of skeletal muscle tissue of Angus heifer calves

The study examined changes in the transcriptional profile of skeletal muscle tissue in heifer calves offered varying planes of nutrition during the early life period. From approximately 3 weeks of age Angus X Holstein-Friesian heifer calves were offered either a high or moderate plane of nutrition to achieve target growth rates of 1.2 kg/d and 0.5 kg/d, respectively. After 18 weeks of differential feeding all calves were euthanized and skeletal muscle tissue samples collexted from each calf. RNA was extracted and subsequently subjected to RNAseq analysis. 482 genes were significantly differentially expressed between calves on the High plane of nutrition and those on the Moderate plane of nutrition. Biological pathway analysis revealed an enrichement from these genes for processes and pathways related to energy production and cellular growth and proliferation. 20 skeletla muscle RNA samples were analysed in this study. 10 samples from each High and Moderate plane of nutrition groups. Calves on the High-plane of nutrition received 1.5 kg of milk replacer (10 liters) per day and ad libitum concentrates during the calf phase. During the subsequent post-weaning phase this group were then offered concentrates ad libitum and hay to appetite. During the calf phase, the Moderate plane of nutrition group received 0.5 kg of milk replacer (4 litres) per day and 1 kg of concentrates, subsequently receiving 1kg of concentrates and hay to appetite during the post-weaning phase. The calf phase lasted for 8 weeks and was followed by the post-weaning phase which lasted for 11 weeks. All samples were collected at the same time-point (21 weeks of age) all differentially expressed genes reported were up- or down-regulated in HP calves compared to MP calves.