Determining the Relationship Among Cattle Genotype, Hair Coat Score, and Productivity Through the Investigation of Single Nucleotide Polymorphisms within Prolactin, Dopamine Receptor D2, and Melatonin Receptor 1A

Abstract

Prolactin (PRL), melatonin (MTN), and dopamine (DA) are all hormones that are believed to play a role in the regulation and growth of hair in beef cattle. There are also single nucleotide polymorphisms associated with each of these hormones or their receptors, indicating that the investigation of these polymorphisms could allow them to serve as genetic markers for the future productivity of an animal. The objective of this study was to determine the relationships among cattle genotype, hair coat score, and productivity through the investigation of single nucleotide polymorphisms within prolactin, dopamine receptor D2, and melatonin receptor 1A. Body weights, hair coat scores, and blood samples were collected in May, June, and July from each non-lactating crossbred beef cow (n=71). The cows were grazing mixed grass pastures that included native endophyte infected tall fescue. Serum PRL, MTN, and DA concentrations were established by validated RIA. Based on the measurements recorded from the May samples, cows were categorized as high (n = 11; 159 ± 29 ng/mL PRL), medium (n = 48; 51 ± 4 ng/mL PRL), or low (n = 12; 21 ± 4 ng/mL PRL). Data were analyzed with Pearson correlations and repeated measures ANOVA with year, month, prolactin category (PRLCAT) and genotype as the main effects. Concentrations of PRL were correlated (r \u3e 0.53; P \u3c 0.0001) over the three months, and May PRL concentrations were correlated (r \u3e 0.29; P \u3c 0.02) with cow body weights in May, June, and July. Cows in the low PRLCAT had lower (