Association of genetic variants of bovine growth hormone with milk production traits in Holstein cattle

Summary Gene and genotype frequencies of alleles, identified by PCR/RFLP technology, at leucine 127/valine127 (L/V) and C/D loci of the growth hormone gene of Ayrshire, Holstein and Jersey breeds were determined. The frequency of the V allele at the L/V mutation locus was 0.29, 0.09 and 0.24 for the Ayrshire, Holstein and Jersey breeds, respectively. The frequencies of the D allele at the C/D mutation locus were 0.00, 0.13 and 0.30 for the three breeds, respectively. Different growth hormone genotypes of Holstein AI bulls were compared for their estimated transmitting abilities (ETA) of milk, fat and protein yields using the samples of unrelated bulls and samples of the top, medium and bottom groups of ETA. The L/V locus was significantly (p < 0.05) associated with fat and protein ETAs of the selected groups and approached significance (p = 0.06) for milk ETA, with the V allele being more frequent in the top than in the bottom group of bulls. The C/D polymorphic locus was significantly (p = 0.02) associated with differences among the top, middle and bottom groups of bulls for milk ETA, but not significantly (p > 0.05) associated with fat and protein ETAs. The results suggest a possible association of growth hormone gene polymorphism with milk production traits in Holstein bulls. However, the results were not conclusive due to the small sample size and low frequencies of the V and D alleles. Much larger sample sizes are needed to obtain a reasonable number of VV and DD genotypes for a critical comparison. Zusammenfassung Zusammenhang genetischer Varianten des Rinderwachstumshormons mit Milchleistungsmerkmalen bei Holstein Rindern Gene und Genotyp Frequenzen von Allelen, identifiziert mittels PCR/RFLP Technik, an Leucin127/Valin127 (L/V) und C/D Loci des Wachtumshormon Genes wurden bei Ayrshire, Holstein und Jerseys bestimmt. Die Häufigkeiten des V Alleles waren 0.29, 0.09 und 0.24, jene des D Alleles 0, 0.13, und 0.30 bei den drei Rassen. Der Vergleich verschiedener Genotypen bei Holstein KB Stieren hinsichtlich geschätzter Nachkommenüberlegenheit (ETA) für Milch, Fett und Protein Mengen umfaßte Stiere mit hohen, mittleren und niedrigen ETA. Der L/V Locus zeigte statistisch signifikanten Einfluß bei Fettund ProteinETA und p = 0.06 bei Milch, wobei das V Allel in der Spitzengruppe häufiger als bei neidrigen war. Der C/D Locus war signifikant (p