Project description:The objective of this study was to examine changes in muscle 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. Muscle biopsies were collected at 2 time points (end of the differential feeding in Period 1 (d 120) and during the realimentation phase in Period 2 (d 15 of re-alimentation). RNA was extracted and muscle gene expression was examined using RNAseq technology and bioinformatic analysis. During the differential feeding period, over-represented pathways including fatty acid beta oxidaiton, oxidative phosphorylation and TCA cyclewere identified, which indicate utilisation of lipid sotes for energy utilisaiton and also alterations in energy produciton during dietary restriciton in muscle. During the realimentation period, pathways involved in energy produciton were over-represented, with the direction of fold changes opposite to that of these pathways in Period 1. additionally, a number of genes involved in cell division and cellular proliferation were up-regulated during compensatory growth in re-alimentation, thereby promoting accelerated cell growth and proliferation in muscle tissue of animals experiencing compensatory growth. 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. 40 muscle RNA samples were analysed in total. 10 samples were from muscle biopsies collected at the end of a period of dietary restriction (d 120) and 10 samples were from muscle biopsis collected during the initial stages of compensatory growth (d 15 of re-alimentation). In addition, RNA was also anlaysed from 10 samples collected from animals fed a libitum at each of these two timepoints.

Project description:The objective of this study was to examine changes in muscle 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. Muscle biopsies were collected at 2 time points (end of the differential feeding in Period 1 (d 120) and during the realimentation phase in Period 2 (d 15 of re-alimentation). RNA was extracted and muscle gene expression was examined using RNAseq technology and bioinformatic analysis. During the differential feeding period, over-represented pathways including fatty acid beta oxidaiton, oxidative phosphorylation and TCA cyclewere identified, which indicate utilisation of lipid sotes for energy utilisaiton and also alterations in energy produciton during dietary restriciton in muscle. During the realimentation period, pathways involved in energy produciton were over-represented, with the direction of fold changes opposite to that of these pathways in Period 1. additionally, a number of genes involved in cell division and cellular proliferation were up-regulated during compensatory growth in re-alimentation, thereby promoting accelerated cell growth and proliferation in muscle tissue of animals experiencing compensatory growth. 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.

Project description:Growing ruminants maintained under dietary restriction for extended periods will exhibit compensatory growth when reverted to ad libitum feeding. This period of compensatory growth is associated with increased feed efficiency, lower basal energy requirements, and changes in circulating concentrations of metabolic hormones. To identify genetic mechanisms contributing to these physiological changes, 8 month-old steers were fed either ad libitum (control; n = 6) or 60-70% of intake of control animals (feed-restricted; n=6) for a period of 12 weeks. All steers were then fed ad libitum for the remaining 8 weeks of the experiment (realimentation period). Liver was biopsied from each animal at days -14, +1 and +14 relative to realimentation for RNA extraction and gene expression analysis by microarray hybridization. Steers were assigned randomly to one of two treatment groups, control or feed-restricted, and housed indoors in individual pens. Steers were acclimated to their pens for 5 d prior to starting the experimental treatments. Feed was offered once daily between 0630 and 0930 and orts from the previous day's feeding were collected and weighed to estimate actual intake. Control animals were fed ad libitum throughout the 20-wk experimental period. Feed-restricted steers were offered 60-70% of intake of control animals for 12 wks to target a limited rate of gain of approximately 0.5 kg/d. Restricted steers were then fed ad libitum for the remaining 8 wks of the experiment (realimentation period). During the first 3 d of realimentation, feed offered to both treatment groups was divided into two equal rations to gradually adjust restricted animals to full intake. Water was offered ad libitum throughout the experimental period. Approximately 200 mg of liver tissue was collected from each steer by needle biopsy using a Tru-Cut biopsy needle at -14, +1, +14 d relative to realimentation. Liver samples were immediately frozen in liquid nitrogen and stored at -80C until RNA isolation. Total RNA was isolated from 36 liver samples using TRIZOL Reagent (Invitrogen Corp., Carlsbad, CA). Samples were DNase-treated using the TURBO DNA-free kit (Ambion, Inc., Austin, TX) according to manufacturerâ??s instructions, followed by column purification using the RNeasy Mini Kit (Qiagen, Valencia, CA). Quality and concentration of RNA were assessed using a 2100 Bioanlayzer (Agilent Technologies, Palo Alto, CA) and ND-1000 spectrophotometer (NanoDrop Technologies, Wilmington, DE). Probe labeling, hybridizations of probes to the oligo microarray, and array scanning were performed by the Roche NimbleGen Systems, Inc. Microarray Core Facility in Reykjavik, Iceland according to standard procedures (Madison, WI; http://www.nimblegen.com).

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RNA-seq analysis of differential gene expression in liver from Holstein Friesian bulls undergoing diet restriction and compensatory growth

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