| Abstrakt: |
In recent years, the aim of dairy cattle breeding was to increase milk productivity traits. However, there is an observed decrease of fertility traits of cows, and, as a result, early culling of animals. This is due to the fact that causes of decreased reproduction are sometimes impossible to determine and its signs are difficult to estimate. One of the causes for decreasing fertility of cows is the decline in the quality of oocytes capable of fertilization. Therefore, a study into the ratio between the number and quality of oocytes capable of fertilization and the level of milk productivity in cows, as well as association with polymorphic variants of the GH, PRL, and Pit-1 genes, is of scientific interest. The aim of this study was to determine the dependence of the quality and quantity of cow COC obtained post mortem on the level of milk productivity and genetic profile for the genes GH, PRL, and Pit-1. There was high frequency of allele L of the GH gene, 0.942; allele A of the PRL gene, 0.889; and allele B of the Pit-1 gene, 0.710. High average content of COC per ovary was obtained in a group of animals with LL genotype of the GH gene (LL to LV +7.54 units, p ≤ 0.05), and a significant portion of them were viable (LL to LV +4.5 units, p ≤ 0.05). In individuals with the AA genotype of the PRL gene, the average number of isolated viable COC per ovary was higher than in those with the AB genotype (+4.84 units, p ≤ 0.05). Analysis of the association of polymorphic variants of the Pit-1 gene with the quantity and quality of COC did not reveal significant differences in the studied group of individuals. Assessment for the relationship of polymorphic variants of the studied genes with the breeding value (BV) indices of milk productivity, milk fat, and protein content showed that only animals with the LV genotype exceeded their peers with the LL genotype of the GH gene in milk fat and protein content by 8.3 kg (p ≤ 0.05) and 6.0 kg (p ≤ 0.01), respectively. Average calculated breeding value based on quantity of COC of individuals in the studied groups revealed no significant difference. [ABSTRACT FROM AUTHOR] |
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