Theoretical and Applied Veterinary Medicine (Jun 2020)
Evaluation of cows’ milk productivity by using genetic markers
Abstract
Presented results of a study on the relationship of various polymorphic variants of the GH and PIT-1 gene with such economically useful traits as milk yield, milk fat and protein content, the yield of milk protein and fat in highly productive half-sibs of Holstein cows. The experimental animals were divided into groups depending on the combination of different allele forms of the GH and PIT-1 genes. The studies were carried out at ZAO Agro-Soyuz, Dnipropetrovsk region. The total sample сonsisted of 136 half-sibs cows, which were daughters of the Holstein bull Cashmere 131671771. All animals were of the same age. The DNA samples extracted from the experimental animals’ blood were subject for the research. To determine the polymorphism of marker genes, the PCR-RFLP method was used. When distributing half-sibs cows on genotypes according to the growth hormone gene GH, were found 124 (91.10%) homozygous animals of LL genotype, 10 (7.50%) heterozygous animals of LV genotype, and 2 (1.40%) homozygous animals of VV genotype. It was established that homozygous half-sibs of LL genotype were dominated over heterozygous half-sibs of LV genotype by milk yield during 303 days for 753 kg (P > 0.99), by the amount of milk fat – for 26.8 kg (P > 0.99), by the amount of milk protein – for 24.7 kg (P > 0.99). An advantage in the main milk productivity indicators of homozygous LL genotype half-sibs of the GH gene over heterozygous LV genotype half-sibs of the GH gene was also observed for 305 days of the second lactation. Heterozygous half-sibs of AB genotype by the PIT-1 gene had an advantage over their peers – homozygous half-sibs of BB genotype, including the milk yield for 425 kg (P > 0.95), the milk fat amount for 16.5 kg (P > 0.95) and the milk protein amount for 14.45 kg (P > 0.99). According to the milk fat and protein content, the difference was not significant. The most pronounced raising effect of the main milk productivity indicators were combinations of GH and PIT-1 paired genes. A part of the complex genotype factor influence on milk yield during 305 days of the first two lactations, the yield of milk fat and protein was about 26.6–30.2% in P> 0.999. The LL homozygosity by the GH gene in combination with the AB and BB genotypes by the PIT-1 gene in the context of the first two lactations was accompanied by higher yield of milk (r = + 0.503 ... 0.505 for P > 0.999), by larger amount of milk fat (r = + 0.503. .. 0.505 for P > 0.999) and milk protein (r = + 0.520 ... 0.530 for P > 0.999). The LL homozygosity by the GH gene in combination with the AB and BB genotypes by the PIT-1 gene in the context of the first two lactations was accompanied by higher yield of milk (r = + 0.503 ... 0.505 for P > 0.999), by larger amount of milk fat (r = + 0.503. .. 0.505 for P > 0.999) and milk protein (r = + 0.520 ... 0.530 for P > 0.999). A statistically significant, direct correlation, average in strength, suggests that the use of genetic markers, in particular GH and PIT-1 genes for growth hormone, will be effective for the selection and subsequent formation of a highly productive herd in the direction of increasing milk productivity.
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