Milk productivity and milk quality of Ukrainian Black-and- White dairy cows with different genotypes of kappa-casein
Iryna Polieva, Igor Korh
Abstract: The results of the investigation of milk production and milk quality of the Ukrainian Black-and-
White dairy cows with different genotypes of kappa-casein have been presented in the article. It has
been found that homozygotes of kappa-casein with genotype AA that are the most common were
more often detected in the actual genetic structure of the experimental herd of cows – 63.1%. The
number of the heterozygotes of kappa-casein with genotype AB was slightly lower – 31.6%. However,
the proportion of the homozygotes that had a rare homozygous genotype BB was 5.3% of the total
number of the array size. The expected genetic structure of the experimental herd of cows approached
the actual values of the array distribution and it was 62.4; 33.2 and 4.4% that indicates the increase
in the role of further selection work in the direction of the wide use of breeding bulls in the custom
mating, the bulls that are primarily the carriers of genotype AB and BB and the consolidation of the
herd by the quality of milk – the cheese suitability of milk. Allele A in the experimental array was
detected with the frequency of 0.79; however, a much lower distribution frequency was represented
by a technologically desirable allelic variant B – 0.21. For 305 days of lactation the amount of milk
obtained from the cows that were the carriers of the genotype AA was more by 204.5 kg or 3.3% than
the amount of milk obtained from the cows with the genotype AB. While the productive potential of
the cows with the genotype BB was significantly lower than the potential of the cows with genotype
AA by 422.8 kg or 6.6% with a statistically significant difference between them in favor of the latter (p
< 0.05). The milk of better quality with higher mass fraction of fat by 0.21% (p < 0.05) was produced
by the cows with genotype BB as compared to the cows that were the carriers of genotype AA,
although the statistical significance of the intergroup difference as for the mass fraction of protein was
significantly higher by 0.42% (p < 0.01) in favor of the former. The effect of kappa-casein genotype on
the mass fraction of protein in milk in the animals with genotype AB against AA was less pronounced
than fat (0.09%), according to which the difference between them of 0.16% was revealed that was also
statistically significant in favor of the former (p < 0.05).
White dairy cows with different genotypes of kappa-casein have been presented in the article. It has
been found that homozygotes of kappa-casein with genotype AA that are the most common were
more often detected in the actual genetic structure of the experimental herd of cows – 63.1%. The
number of the heterozygotes of kappa-casein with genotype AB was slightly lower – 31.6%. However,
the proportion of the homozygotes that had a rare homozygous genotype BB was 5.3% of the total
number of the array size. The expected genetic structure of the experimental herd of cows approached
the actual values of the array distribution and it was 62.4; 33.2 and 4.4% that indicates the increase
in the role of further selection work in the direction of the wide use of breeding bulls in the custom
mating, the bulls that are primarily the carriers of genotype AB and BB and the consolidation of the
herd by the quality of milk – the cheese suitability of milk. Allele A in the experimental array was
detected with the frequency of 0.79; however, a much lower distribution frequency was represented
by a technologically desirable allelic variant B – 0.21. For 305 days of lactation the amount of milk
obtained from the cows that were the carriers of the genotype AA was more by 204.5 kg or 3.3% than
the amount of milk obtained from the cows with the genotype AB. While the productive potential of
the cows with the genotype BB was significantly lower than the potential of the cows with genotype
AA by 422.8 kg or 6.6% with a statistically significant difference between them in favor of the latter (p
< 0.05). The milk of better quality with higher mass fraction of fat by 0.21% (p < 0.05) was produced
by the cows with genotype BB as compared to the cows that were the carriers of genotype AA,
although the statistical significance of the intergroup difference as for the mass fraction of protein was
significantly higher by 0.42% (p < 0.01) in favor of the former. The effect of kappa-casein genotype on
the mass fraction of protein in milk in the animals with genotype AB against AA was less pronounced
than fat (0.09%), according to which the difference between them of 0.16% was revealed that was also
statistically significant in favor of the former (p < 0.05).
Keywords: allelle; dairy productivity; genotype; kappa-casein; milk quality; PCR-RFLP
Date published: 2021-06-29
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