Abstract
A previous study in cattle based on >48,000 markers identified markers on chromosome 4 near the chemerin gene associated with average daily feed intake (ADFI) in steers (P < 0.008). Chemerin is an adipokine associated with obesity and metabolic syndrome in humans, representing a strong candidate gene potentially underlying the observed association. To evaluate whether the bovine chemerin gene is involved in feed intake, 16 markers within and around the gene were tested for association in the same resource population. Eleven were nominally significant for ADFI (P < 0.05) and two were significant after Bonferroni correction. Two and five SNP in this region were nominally significant for the related traits of average daily gain (ADG) and residual feed intake (RFI), respectively. All markers were evaluated for effects on meat quality and carcass phenotypes. Many of the markers associated with ADFI were associated with hot carcass weight (HCW), adjusted fat thickness (AFT), and marbling (P < 0.05). Marker alleles that were associated with lower ADFI were also associated with lower HCW, AFT, and marbling. Markers associated with ADFI were genotyped in a validation population of steers representing 14 breeds to determine predictive merit across populations. No consistent relationships for ADFI were detected. To determine whether cattle feed intake or growth phenotypes might be related to chemerin transcript abundance, the expression of chemerin was evaluated in adipose of 114 heifers that were siblings of the steers in the discovery population. Relative chemerin transcript abundance was not correlated with ADFI, ADG, or RFI, but associations with body condition score and yearling weight were observed. We conclude that variation in the chemerin gene may underlie observed association in the resource population, but that additional research is required to determine if this variation is widespread among breeds and to develop robust markers with predictive merit across breeds.
Highlights
Beef cattle producers could increase profitability by selecting for animals with increased feed efficiency, and genetic markers for animals with superior performance may facilitate selection
Fourteen additional publicly available SNP located up- and down-stream of the chemerin gene from 113.54–113.62 Mb were included in the genotyping assays (Table 2)
Several markers on the Illumina BovineSNP50 BeadChip located near the chemerin gene on BTA4 were previously found to be associated with Average daily feed intake (ADFI) (P = 0.001–0.008) in the discovery population of steers (Snelling et al, 2011)
Summary
Beef cattle producers could increase profitability by selecting for animals with increased feed efficiency, and genetic markers for animals with superior performance may facilitate selection. In a previous genome-wide association study, four markers from the Illumina BovineSNP50 BeadChip mapping to bovine chromosome 4 (BTA4) between 113.3 and 113.6 Mb (UMD 3.1, genome assembly, Zimin et al, 2009) were nominally significant (P ≤ 0.008) for ADFI in a USMARC population of crossbred steers (Snelling et al, 2011). The genes residing within this region included: 10 transfer RNA genes, three zinc finger genes involved in DNA and metal ion binding, KRAB-A domain containing 1 gene, the SCO-spondin homolog gene, ATPase, H + transporting V0 subunit e2, leucine rich repeat containing 61, chromosome 4 open reading frame, human C7orf (C4H7orf29) gene, and the chemerin (RARRES2) gene. The adipokine, chemerin, known as retinoic acid receptor responder 2 (RARRES2) or tazarotene-induced gene 2 protein (TIG2), is located within this region on BTA4 at 113.5 Mb, and is a cytokine produced by adipose tissue. Circulating levels of chemerin have been associated with symptoms of metabolic syndrome in humans including; body mass index (BMI), fasting serum insulin, triglycerides, and HDL cholesterol (Bozaoglu et al, 2007, 2009), making it an www.frontiersin.org
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