Association Between the Growth Hormone Releasing Hormone (GHRH) Gene Polymorphism and Milk Production Traits of Dairy Cattle

The association between the GHRH/HaeIII gene polymorphism and milk production traits of Polish Holstein and Jersey cows were analysed. A total of 427 animals were included in the study. A PCR-RFLP method was used for genotyping. The frequencies of genotypes and alleles for the Polish Holstein cows were 0.078 - AA, 0.339 - AB, 0.583 - BB and 0.248 - GHRH(A), 0.752 - GHRH(B). For the Jersey cows, the frequencies were: 0.032 - AA, 0.427 - AB, 0.541 - BB and 0.246 - GHRH(A), 0.754 - GHRH(B). In all lactations, the Jersey cows with AA genotype exhibited the highest milk fat content. In the 2(nd) and 3(rd) lactations the AA Jersey cows had lower milk yields compared with the AB/BB cows. However, Polish Holstein cows did not exhibit such effects of genotypes on milk yield/traits. It still remains unclear that the analysed polymorphism could influence to the physiology of milk fat production.