Effect of early-life plane of nutrition on the hepatic transcriptional profile in heifer calves

The objective of this study was to examine changes in hepatic gene expression of heifer calves offered varying planes of nutrition during early life. At approximately 3 weeks of age (19 ± 5 days of age) Angus X Holstein-Friesian heifer calves were offered a high (HP, n=15) or moderate plane of nutrition (MP, n=15) 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 the liver of each calf recovered. RNA was extracted and subsequently subjected to RNAseq analysis. A total of 591 genes were identified as significantly differentially expressed between HP and MP calves. Differentially expressed genes were involved in biological pathways and processes including those related to metabolism (amino acid, vitamin and mineral metabolism) as well as those involved in organ growth and development. Overall design: 30 liver RNA samples were analyzed 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.