THE EFFECTS OF POLYMORPHISM IN THE DGAT1 GENE ON ENERGY BALANCE AND MILK PRODUCTION TRAITS IN PRIMIPAROUS HOLSTEIN COWS DURING THE FIRST SIX MONTHS OF LACTATION

L. Stadnik, D. Nemeckova, K. Jecminkova, V. Kadlecova

Abstract: The aim of this study was to analyze the effects and significance of DGAT1 K232A polymorphism on milk production traits – milk yield, content of protein, fat and fat-to-protein ratio in milk during the first six months of lactation, with respect to the course of the body condition. The influence of year, calving season and month of lactation on these traits was also assessed. The investigation was conducted on 246 primiparous Holstein cows, calved from 2009 to 2011. DGAT1 genotypes were identified using the polymerase chain reaction – the restriction fragment length polymorphism technique (PCR-RFLP). The A and K allele frequencies were 0.73 and 0.27. Homozygotes KK were characterized by significantly (P<0.01- 0.05) highest milk fat content during the whole observed period on average as well as in almost all individual months after parturition. Homozygotes AA reached significantly highest average milk yield in almost all observed months and in the whole observed period (P<0.01- 0.05), which is related to statistically significantly (P<0.01- 0.05) lowest percentage content of milk components - protein, fat and fat-to-protein ratio in cows of this allelic variant. The low fat-to-protein ratio indicates a positive effect of the AA genotype on body condition score changes reflecting energy balance level. The most intensive body condition score changes occurred in homozygotes KK during the first month of lactation but this was not significantly different. Average daily milk production annually significantly increased (P<0.01) as well as intensity of body condition score changes (P<0.01). The most significant body condition changes were detected during the summer months.

Keywords: body condition score; dairy - cows; DGAT1; genetic polymorphisms; indicators of milk production traits; negative energy balance; PCR-RFLP

Date published: 2017-10-26