Abstract
The aim of this study was to investigate the effect of early calf-hood nutrition on the transcriptomic profile of the arcuate nucleus of the hypothalamus, anterior pituitary and testes in Holstein-Friesian bulls. Holstein-Friesian bull calves with a mean (±S.D.) age and bodyweight of 19 (±8.2) days and 47.5 (±5.3) kg, respectively, were offered a high (n = 10) or low (n = 10) plane of nutrition in order to achieve an overall growth rate of 1.2 and 0.5 kg/day. At 126 (±3) days of age, calves were euthanized, hypothalamus (arcuate region), anterior pituitary and testicular parenchyma samples were harvested and RNAseq analysis was performed. There were 0, 49 and 1,346 genes differentially expressed in the arcuate nucleus, anterior pituitary and testicular tissue of bull calves on the low relative to the high plane of nutrition, respectively (P < 0.05; False Discovery Rate <0.05). Cell cycle processes in the anterior pituitary were down regulated in the low relative to the high plane of nutrition; there was no differential expression of genes related to reproductive processes. Gene expression involved in cholesterol and androgen biosynthesis in the testes were down regulated in animals on the low plane of nutrition. This study provides insight into the effect of early life plane of nutrition on the regulation of the HPT axis.
Highlights
Dairy bulls are selected as potential artificial insemination (AI) sires soon after birth using genomic selection[1]
There was no effect of nutritional treatment on follicle stimulating hormone (FSH), luteinizing hormone (LH) or testosterone (P > 0.05) but there was an effect of week of sampling on all three hormones (P < 0.0001; Supplementary Fig. 1)
Male infertility function was predicted to be decreased (z-score: −2.236) in the low compared to the high plane of nutrition group. This is the first study to investigate the effect of plane of nutrition during the early calf-hood period on the transcriptomic profile of the HPT axis in young bulls
Summary
Dairy bulls are selected as potential artificial insemination (AI) sires soon after birth using genomic selection[1]. There is increasing evidence for a positive effect of the plane of nutrition during calfhood on the early onset of puberty in the bull[2,3,4] It is desirable for such bulls to reach puberty earlier and that they have the capability of producing high volumes of good quality semen early in life, within the context of seasonal dairy production systems. Metabolic signals are sent from organs such as the liver (IGF-1), pancreas (insulin) and adipose tissue (leptin, adiponectin) and received by metabolic sensing neurons involved in satiety and energy homeostasis within the arcuate (ARC) nucleus Such biochemical messages are mediated by proteins including neuropeptide Y (NPY), agouti-related protein (AgRP)[7,8] as well as kisspeptin (Kiss)[9,10]. We have recently demonstrated that Holstein-Friesian bulls fed a high plane of nutrition for the first six months of life reached puberty approximately one month earlier than bulls on a lower plane irrespective of their plane of nutrition during the subsequent months[2]
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