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DNA polymorphisms and transcript abundance of PRKAG2 and posphorylated AMP-activated protein kinase in the rumen are associated with gain and feed intake in beef steers

A. K. Lindholm-Perry, L. A. Kuehn, W. T. Oliver, R. J. Kern, R. A. Cushman, J. R. Miles, A. K. McNeel, H. C. Freetly
Animal genetics 2014 v.45 no.4 pp. 461-472
AMP-activated protein kinase, DNA, average daily gain, beef cattle, feed conversion, feed intake, gene expression, genes, liver, loci, phenotype, rumen, single nucleotide polymorphism, small intestine, steers
Beef steers with variation in feed efficiency phenotypes were evaluated previously on a high density SNP panel. Ten markers from rs110125325-rs41652818 on bovine chromosome 4 were associated with average daily gain (ADG). To identify the gene(s) in this 1.2Mb region responsible for variation in ADG, genotyping with 157 additional markers was performed. Several markers (n=41) were nominally associated with ADG and three of these, including the only marker to withstand Bonferroni correction, were located within the protein kinase, AMP-activated, gamma 2 non-catalytic subunit (PRKAG2) gene. An unrelated population of crossbred steers (n=406) was genotyped for validation. One marker located within the PRKAG2 loci approached significant association with gain. To evaluate PRKAG2 for differences in transcript abundance, we measured expression in the liver, muscle, rumen and intestine from steers (n=32) with extreme feed efficiency phenotypes collected over two seasons. No differences in PRKAG2 transcript abundance were detected in small intestine, liver, or muscle. Correlation between gene expression level of PRKAG2 in rumen and average daily feed intake (ADFI) was detected in both seasons (P<0.05); however, the direction differed by season. Lastly, we evaluated AMP-activated protein kinase (AMPK), of which PRKAG2 is a subunit, for differences among ADG and ADFI and found that the phosphorylated form of AMPK was associated with ADFI in the rumen. These data suggest that PRKAG2 and its mature protein, AMPK are involved in feed efficiency traits in beef steers. This is the first evidence to suggest that rumen AMPK may be contributing to ADFI in cattle.