GSE64285
RNA-seq analysis of differential gene expression in liver from Holstein Friesian bulls undergoing diet restriction and compensatory growth
The objective of this study was to examine changes in hepatic gene expression of growing bulls during a period of dietary energy restriction followed by a period of subsequent realimentation and compensatory growth. Purebred Holstein Friesian bulls (n=20) were assigned to one of two feeding treatments (i) restricted feed allowance for 125 days (n=10) followed by ad libitum access to feed for a further 55 days or (ii) a control group with ad libitum access to feed through out the 180 days trial (n=10).  The first 125 days of the trial were denoted as Peirod 1, during which treatment groups were fed differentially. The subsequent 55 days, denoted as Period 2 during which all bulls were fed ad libitum. All bulls received the same diet of 70% concentrate 30% grass silage through out the experimental trial,with the amount of feed provided different dependnet on each treatment group. At the end of each period, 10 animals from each treatment group (10, restricted fed and 10 ad libitum fed) were slaughtered and hepatic tissue collected within thirty minutes of slaughter. RNA was extracted and hepatic gene expression was examined using RNAseq technology and bioinformatic analysis. During the differential feeding period, over-represented pathways including amino acid and lipid metabolism, protein synthesis and cell cycle/proliferation were identified, which indicate alterations in metabolic and growth rate in the liver during dietary restriction . During the realimentation period, pathways involved in cell cycle and cell growth as well as protein synthesis were over-represented, with the direction of fold changes opposite to that of these pathways in Period 1. This information can be exploited in genomic breeding programmes to assist selection of cattle with a greater ability to compensate following a period dietary restriction. Overall design: 40 liver RNA samples were analysed in total. 10 samples were from liver biopsies collected at the end of a period of dietary restriction (d 125) and 10 samples were from liver biopsis collected after 55 days of compensatory growth (d 55 of re-alimentation). In addition,  RNA was also analyzed from 10 samples collected from animals fed ad libitum at each of these two timepoints.