Investigation of allele frequencies of the growth hormone receptor (GHR) F279Y mutation in dairy and dual purpose cattle breeds

Abstract

A major QTL for milk production traits was reported in the middle of bovine chromosome 20 and, for its map position, the growth hormone receptor (GHR) gene was considered a strong positional and functional candidate gene. A missense mutation in exon VIII (F279Y amino acid substitution) showed highly significant effects mainly on milk composition (protein percentage and fat percentage) as well as on milk yield in several dairy cattle populations. As no information about the frequency of these two GHR alleles is available in any population, we studied their distribution in dairy and dual purpose cattle breeds reared in Italy. A total of 679 animals belonging to seven cattle breeds (Italian Holstein-Friesian, n=108; Italian Brown, n=104; Italian Simmental, n=104; Jersey, n=104; Reggiana, n=108; Modenese, n=66; Rendena, n=85) were sampled. A new PCR-RFLP protocol was designed to analyse this mutation inserting an artificial restriction site for enzyme SspI. In all investigated breeds, allele F was the most frequent and ranged from 0.947 (Italian Brown and Jersey) to 0.727 (Italian Holstein-Friesian). In Rendena, Italian Simmental, Reggiana and Modenese it was 0.824, 0.909, 0.921 and 0.924, respectively. For all breeds no significant deviation from the Hardy-Weinberg equilibrium was observed. Differences in allele frequencies were statistically significant between the Italian Holstein Friesian and Rendena against all other breeds. Due to the high frequency of the putative positive allele for milk protein percentage the use of the GHR F279Y marker in marker assisted selection plans should not have a great impact on this trait in the studied breeds.