The effect of the neurotensin gene on growth and carcass traits in beef cattle

Abstract

Neurotensin (NTS) is a tridecapeptide which is widely distributed in the central nervous system and digestive tract. It is highly expressed in neurons of the hypothalamus, a region of the brain known to control feeding behavior. Several studies have shown that intracerebroventricular injection of NTS decreased food intake in rats. NTS was therefore characterized and analyzed for associations with growth and carcass traits in beef cattle.NTS mRNA was successfully isolated from brain, spinal cord, abomasum, rumen wall, small intestine and skin samples. The complete bovine mRNA sequence was obtained from skin, along with partial genomic sequence. Three single nucleotide polymorphisms (SNPs) in the 3’ untranslated region (3’UTR) and six intronic SNPs were identified. The three SNPs in the 3’UTR were not in linkage disequilibrium. Of the three SNPs in the 3’UTR, two had minor allele frequencies of 2% and therefore were not analyzed further. The minor allele frequencies for the third SNP (*419G>A) ranged between 0% and 23% for four major beef breeds. The *419G>A SNP was also used to map NTS to bovine chromosome five between markers BM6026 (13 cM, LOD=4.03) and RM103 (4 cM, LOD=3.63).No significant associations between the *419G>A SNP and growth traits were identified. Statistical analysis revealed significant genotype associations for rib eye area (REA), grade fat and moisture in the Canadian Beef Reference Herd (CBRH). These associations were not verified in a second group of purebred yearling bulls. However, significant associations with end of trial fat, %fat and fat deviation were associations for marbling and quality grade. In all cases the AA genotype was associated with increased fat.Although significant associations between carcass measurements and genotype at the *419G>A SNP were present in some populations, none of these associations were found in more than one population. It was therefore concluded that the *419G>A SNP on the bovine NTS gene does not prove to have an economic advantage to the beef cattle industry.