PHENOTYPIC VARIABILITY OF SPERM PRODUCTIVITY OF BULL-SIRES OF DIFFERENT DIRECTIONS OF PRODUCTIVITY
Significant breeds and age features of sperm productivity were found in breeding bulls. The volume of ejaculate and the total number of sperm in it increases until the age of 8–9 years, depending on the breed. The ejaculate volume of 2-year-old bulls, depending on the breed, was 58.63–73.0% and 3-year-old bulls – 69.1–87.0% of the ejaculate volume of 6-year-old offspring, and the total number of sperm in the ejaculate – respectively 53.9–75.4 and 59.5–90.4% of this number of sperm in the ejaculate of 6-year-old bulls. These indicators with small fluctuations persist until 10–12 years of age of the offspring. Sperm concentration and motility also increase until 6–8 years of age and remain at this level with small fluctuations until 12 years of age. The resistance of sperm to freezing reaches its maximum values at the age of 5–6 years of bulls. Analysis of the data shows that the degree of influence of age on the volume of ejaculate, depending on the breed is in the range of 24.2–30.1%, on the concentration of sperm – 2.6–15.2, their total number in the ejaculate – 13.8–21.2, sperm motility – 4.3–18.3 and the resistance of sperm to freezing – 8.5–15.8%.
According to the results of research, the correlation coefficient between age and ejaculate volume for bulls of the studied breeds was 0.43–0.60, and between age and the total number of sperm in the ejaculate – 0.37–0.48. There is a significant dependence of ejaculate volume and total sperm count on the live weight of the fetuses. The correlation coefficient between ejaculate volume and live weight, depending on the breed, was 0.51–0.75, and for the total amount in ejaculate – 0.45–0.55. The share of live weight on ejaculate volume was 25.0–43.1%, and on the total number of sperm in ejaculate – 20.8–36.9%. This close relationship can be explained by the fact that the weight of the testes has a high relationship with the live weight of the ovary (r = 0.89).
The results of research show that the semen of breeding bulls of different breeds has different morphological composition. The largest number of sperm abnormalities occurs in isolated heads (3.5 ± 0.14%), curved bodies (2.7 ± 0.19%), twisted (1.6 ± 0.14%), bent (1.7 ± 0.14%) and folded (3.4 ± 0.40%) tails. The sum of primary anomalies was significantly less than the sum of secondary anomalies.
When dividing pathological forms into pathology of the head, neck, body and tail, it was found that the total amount of abnormal forms of sperm was the largest in bulls of limousine breed (16.6 ± 2.19) and the smallest – in the offspring of Aberdeen Angus and Simmental breeds. The largest number of pathological forms of sperm heads were bulls of Hereford breed (7.0 ± 0.55%), and the smallest – the offspring of Aberdeen Angus breed (4.2 ± 0.83%), the difference is statistically significant at P < 0.005. The sum of primary anomalies was highest in bulls of Limousine breed (2.9 ± 1.03) and Dutch breed (2.1 ± 0.42), and secondary anomalies – in bulls of Limousine breed (13.7 ± 1.87) and Piemontese breed (13.7 ± 2.19%).
During the correlation-regression analysis, the closest correlation was established between the motility of germ cells after thawing and the number of pathologies of the heads (r = -0.43 at P < 0.05), cervical sperm (r = -0.44 at P < 0,05) and the total amount of pathological forms (r =
-0.45 at P < 0.005). Average correlations were observed between the number of pathologies of the heads and necks of sperm and the motility of germ cells in native semen (respectively r = -0.31 and r = -0.30 at P < 0.05), pathologies of the heads – -0.30 at P < 0.005) and the total amount of pathological forms of sperm (r = -0.23 at P > 0.05) and the amount of rejected sperm. The share of the influence of the age of bulls on the number of pathological forms of the heads was 24.0% (P < 0.05), pathologies of the necks – 4.0% (P > 0.05), the body – 26.0% (P < 0.05), tail – 37.0% (P < 0.01) and the total number of pathological forms of sperm – 59.0% (P < 0.001).
Conclusions. Age and breed features of quantitative and qualitative indicators of sperm productivity, growth of genitals, morphological composition of spermatozoa and correlations between these indicators in bulls of different breeds have been established.
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