Abstract
Compensatory growth (CG), an accelerated growth phenomenon which occurs following a period of dietary restriction is utilised worldwide in animal production systems as a management practise to lower feed costs. The objective of this study was to evaluate the contribution of jejunal epithelial to CG in cattle through transcriptional profiling following a period of dietary restriction as well as subsequent re-alimentation induced CG. Sixty Holstein Friesian bulls were separated into two groups; RES and ADLIB, with 30 animals in each. RES animals were offered a restricted diet for 125 days (Period 1) followed by ad libitum feeding for 55 days (Period 2). ADLIB animals had ad libitum access to feed across both periods 1 and 2. At the end of each period, 15 animals from each treatment group were slaughtered, jejunal epithelium collected and RNAseq analysis performed. Animals that were previously diet restricted underwent CG, gaining 1.8 times the rate of their non-restricted counterparts. Twenty-four genes were differentially expressed in RES compared to ADLIB animals at the end of Period 1, with only one gene, GSTA1, differentially expressed between the two groups at the end of Period 2. When analysed within treatment (RES, Period 2 v Period 1), 31 genes were differentially expressed between diet restricted and animals undergoing CG. Dietary restriction and subsequent re-alimentation were associated with altered expression of genes involved in digestion and metabolism as well as those involved in cellular division and growth. Compensatory growth was also associated with greater expression of genes involved in cellular protection and detoxification in jejunal epithelium. This study highlights some of the molecular mechanisms regulating the response to dietary restriction and subsequent re-alimentation induced CG in cattle; however the gene expression results suggest that most of the CG in jejunal epithelium had occurred by day 55 of re-alimentation.
Highlights
In the wild, animals encounter periods of nutrient abundance as well as times of nutrient deficiency
The gastrointestinal tract has previously been shown to be one of the most responsive organs to both dietary restriction and subsequent compensatory growth (CG) [3,4,5,6], our attention was focused on examining the transcriptional profile of the jejunum, which is of primary importance as a site of digestion and in the absorption of nutrients through the intestinal wall
Following a period of dietary restriction, genes associated with metabolism and digestion were down-regulated in response to reduced dietary intake
Summary
Animals encounter periods of nutrient abundance as well as times of nutrient deficiency. Molecular control of compensatory growth in cattle the capacity to display accelerated tissue growth and deposition during times of elevated nutrient abundance [1]. The occurrence of CG has been incorporated into many livestock production systems, for cattle as a method to reduce feed input costs [2]. This naturally occurring phenomenon is utilised worldwide [3,4,5,6], there is a dearth of knowledge in relation to the molecular control regulating the expression of the trait in cattle. Further investigations into the molecular expression of this trait in other metabolically important tissues is warranted, as a greater understanding of the control of CG at the molecular level would lead to better exploitation and possible incorporation of this economically important trait into genomic selection breeding programs for beef cattle
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