Association between the growth hormone releasing hormone (GHRH) gene polymorphism and milk production traits of dairy cattle.

Szatkowska, I., Dybus, A., Grzesiak, W., J“drzejczak, M. and Muszy½ska, M. 2009. Association between the growth hormone releasing hormone (GHRH) gene polymorphism and milk production traits of dairy cattle. J. Appl. Anim. Res., 36: 119-123. 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.