Identification of Polymorphisms in the Enhancer Region of the Bovine Prolactin Gene and Association with Profitability Traits of Beef Cattle1

Objectives were to investigate the polymorphic nature of the enhancer region of the bovine prolactin (PRL) gene and evaluate these polymorphisms as potential markers of profitability traits in beef cows and calves. Primers were designed to amplify a 500-bp fragment 892 to 1,392 bases upstream of the bovine PRL gene. Two single nucleotide polymorphisms were identified at positions -1,286 (cytosine to thymine; c1286t) and -1,167 (adenine to guanine; a1167g). In the discovery population, genomic DNA was obtained from purebred Angus, purebred Brahman, and their reciprocal cross cows. Cows were assigned to graze either common bermudagrass or toxic endophyte-infected tall fescue for their lifetime. Weaning weight and hip height of calves, and lifetime calving rate were recorded. In the validation population, genomic DNA was collected from Brahman-influenced crossbred cows in either low or moderate body condition at breeding. Calving rate, diameter of the largest follicle, and Julian calving date were determined. In the discovery population, homozygous thymine cows at c1286t that grazed endophyte-infected tall fescue had reduced (P = 0.07) calving rates during their lifetime when compared with those of all other genotypes grazing either forage type. Cows in low body condition that were either heterozygous or homozygous for the minor allele of the a1167g genotype calved 22 d later (P ≤ 0.07) than all other cows in the validation population. Identification of cows with specific genotypes within the enhancer region of the PRL gene may serve as a marker of profitability traits and assist beef producers in selecting cattle that may have increased performance