Effect of early-life plane of nutrition on the transcriptional profile of visceral adipose tissue in heifer calves

The aim of this study was to examine changes in the transcriptional profile of visceral adipose tissue in heifer calves offered varying planes of nutrition during the early life period. From approximately 3 weeks of age (19 ± 5 days of age) Angus X Holstein-Friesian heifer calves were offered either a high (HP, n=15) or moderate (MP, n=15) 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 visceral adipose tissue samples harvested from each calf. RNA was extracted and subsequently subjected to RNAseq analysis. A total of 1052 genes were identified as 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 including Sirtuin signalling, oxidative phosphorylation and adipogenesis. In total 30 visceral adipose RNA samples were analysed in total. 15 samples were derived from calves fed the High plane of nutrition (HP, n=15) and 15 samples were derived from the claves fed the Moderate plane of nutrition (MP, n=15). 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.