Associations of melanocortin 1 receptor genotype with growth and carcass traits in beef cattle

Abstract

Melanocortin 1 Receptor (MC1R) is considered to be the main gene controlling the production of eumelanin or phaeomelanin, resulting in black or red coat colour of cattle. The recessive red allele, e, codes for a nonfunctional receptor, which does not bind the agonist alpha-melanocyte stimulating hormone (α-MSH), allowing for the production of phaeomelanin, or red pigment, whereas the dominant ED allele binds α-MSH leading to the production of eumelanin. We hypothesized that black cattle would have more α-MSH bound to MC1R, which could result in more α-MSH binding to the appetite suppressing receptor, Melanocortin 4 Receptor. We genotyped 328 crossbred steers of various colours that were purchased at weaning and fed until slaughter. Black cattle of ED/ED or ED/e genotype had increased back fat and required significantly fewer days (15-25) on feed to reach a target fat level for slaughter than the red cattle. Red cattle of e/e genotype were found to have a significantly larger longissimus dorsi (l. dorsi), shipping weight and hot carcass weight. Differences were comparable whether black versus red coat colour or MC1R genotype were used as the criteria for the group of cattle. Key words: Coat colour, MC4R, MC1R, α-MSH, shipping weight