Effect of early-life plane of nutrition on the transcriptional profile  of the anterior pituitary gland in heifer calves
The aim of this study was to examine changes in the transcriptional profile of the anterior pituitary gland of 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=13) 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 anterior pituitary tissue samples harvested from each calf. RNA was extracted and subsequently subjected to RNAseq analysis. A total of 195 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 related to growth and reproductive system development. Overall design: 28 anterior pituitary RNA samples were analyzed in total, 13 from High plane of nutrition group and 15 from the Moderate plane of nutrition group.  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.