Yield and composition of milk from Polish Holstein-Friesian and Jersey cows in particular months of the first lactations as dependent on milk protein polymorphism

The experiment was performed on 121 primiparous Polish Holstein-Friesian (PHF) cows and 36 primiparous Jersey (JER) cows. The highest decrease in casein yield was noted in JER cows at 7.36% on day 90 of lactation, 15.95% on day 150, 26.78% on day 210, 37.01% on day 270 and 39.67% on day 330. In PHF cows this decrease was substantially lower, at 4.98%, 7.65%, 8.72%, 10.50% and 16.19% respectively. The casein content of milk from prmtiparous PHF cows ranged from 2.38% (LGB - day 60) to 3.09% (LGB BB - day 330), and it was found to be considerably lower in JER cows, varying between 2.35% (CSN3 BB - day 30) and 3.61% (CSN3 BB - day 210). The highest casein yield was recorded in PHF cows with the following genotypes: LGB AA (day 60), CSN1S1 BB (day 60), CSN2 AB (day 270), CSN3 BB (day 150). In JER cows the highest casein yield was noted on day 90 of lactation with respect to the following genotypes: LGB BB, CSN1S1 BC, CSN2 AA and CSN3 BB. In PHF cows the greatest effect on whey protein yield was exerted by the following genotypes: LGB AA (day 90), CSN1S1 BC (day 60), CSN2 AA (day 90); the CSN3 BB genotype influenced whey protein yield in cattle of both breeds (day 90). In JER cows the highest daily yield of whey proteins was observed on day 90 of lactation, with regard to the following genotypes: LGB 1313, CSN1S1 BC, CSN2 AB and CSN3 BB.