Association between polymorphisms in somatotropic axis genes and fertility of Holstein dairy cows

Abstract The aim of this study was to determine the effect of growth hormone receptor (GHR) Alu I, insulin-like growth factor type 1 (IGF-I) Sna BI, and signal transducer and activator 5A (STAT5A) Bst EII polymorphisms in the reproductive performance of Holstein dairy cows and the frequency of this genotypes in cows managed in different systems. This work studied 381 and 506 Holstein cows from semiextensive and intensive systems, respectively. The frequency of genotypes GHR Alu I (+/−), IGF-I Sna BI (−/−) and (+/−), and STAT5A Bst EII (−/−) was higher in animals from semiextensive system, whereas the frequency of the genotypes GHR Alu I (+/+) and IGF-I Sna BI (+/+) was higher in animals from intensive system (P  STAT5A Bst EII (−/−) genotype had a longer calving-first heat interval (P = 0.03). In conclusion, there was no association between the genotypes of GHR Alu I and IGF-I Sna BI and fertility of Holstein cows raised in semiextensive or intensive regimes, although the genotype frequencies of the evaluated polymorphisms were different between the studied systems. The STAT5A Bst EII polymorphism was associated with calving-first heat interval in Holstein cows raised in the intensive system, indicating that this gene could be a molecular marker for genetic selection to improve reproductive performance.