Genetic polymorphism of prolactin and nitric oxide synthase in Holstein cattle.

BACKGROUND AND AIM

Bacterial and viral infections affect the welfare of animals and lead to large economic losses in dairy cattle breeding due to decreased productive indicators and increased culling rates. In modern dairy farming, farmers are looking for effective solutions to prevent and minimize infectious disease risks. To this end, the most relevant study field is the search for gene sites that impact production and health. This study aimed to determine the nature of the distribution of the relative frequencies of alleles and genotypes of polymorphic prolactin () and nitric oxide synthase () in Holstein cows and identify the relationship of these genes with resistance to mastitis and bovine leukemia.

MATERIALS AND METHODS

For this study, we chose cows because infectious diseases affect the amount of lactation and milk quality. Holstein cattle with mastitis and bovine leukemia were selected. Animal genotypes were determined by restriction fragment length polymorphism (RFLP) of polymerase chain reaction (PCR) products. The results were analyzed using a nonparametric statistical method using Microsoft Excel 2010 and Statistica 6.0.

RESULTS

In healthy animals, 94 genotypes were identified for both genes under study. For , -RsaI (72) was the most common genotype and -RsaI (4) the least; for , HinfI (47) was the most common genotype and HinfI the least (21). In animals with leukemia, 34 genotypes were identified. For , -RsaI (25) was the most common genotype and -RsaI (2) the least; for , HinfI (17) was the most common genotype and HinfI (3) the least. In animals with mastitis, 67 genotypes were identified. For , -RsaI (43) was the most common genotype and -RsaI (6) the least; for , HinfI (31) was the most common genotype and -HinfI (7) the least. The distribution of genotypes of polymorphic and generally coincides, and -RsaI is the most common genotype. In groups of sick animals, the number of HinfI homozygotes was lower than that of the control group. In particular, the proportion of animals with the HinfI genotype with bovine leukemia was 8.7% and with mastitis was 10.3% compared with 22.4% in healthy animals. These data support the possible association of the HinfI genotype with resistance to infection. The frequency of the -RsaI allele was higher in groups of sick animals. This allele is associated with increased milk productivity, suggesting that highly productive animals are less resistant to the incidence of viral bovine leukemia and mastitis of bacterial etiology.

CONCLUSION

DNA amplification of Holstein cattle for the polymorphic regions of and using the PCR-RFLP method revealed a possible connection between the distribution of relative allele frequencies of and and resistance to viral and bacterial infections. Thus, in groups of sick animals, the frequency of RsaI, associated with increased milk production compared with the theoretically calculated equilibrium value was higher and the number of homozygotes HinfI was lower than in the control group. In conclusion, animals with increased milk production were more prone to diseases, such as mastitis and bovine leukemia.