SEASONAL CHANGES IN THE REPRODUCTIVE CAPACITY OF BULLS-SIRES
The article presents data on the influence of the month of the year on the quality indicators of sperm production of bulls. The studies were conducted on Holstein, Black-and-White, Brown Swiss, and Hereford bulls at the age of 2-6 years in LLC «Nizhegorodskoe» on breeding work. The statistically significant influence of the month on sperm concentration, activity, and the volume of the ejaculate was established. In most bulls, the sperm concentration in the ejaculate in the winter and early spring was reduced; in the summer months, it increased, reaching a maximum in June - 0,886 ± 0,029 billion/ml. The influence of the month of the year on the sperm concentration was 28,18 %. Changes in the sperm concentration in the Hereford breed are not subject to seasonal influences. The average volume of ejaculate for all bulls at the beginning of the year was relatively high - 7,69-8,45 ml. However, in June, there was a sharp decrease in volume to 5,72 ± 0,213 ml, and in the following months, we saw a gradual increase in volume, the influence of month of the year on the ejaculate volume was 19,73 %. The sperm activity at the beginning of the year was not great - 5,98 ± 0,136 points, in March, there was an increase to 6,33 ± 0,126 points, and in July to 6,47 ± 0,121 points, this period was characterized by maximum activity. After July, there was a decrease in the activity, and in December, it reached the level of 5,95 ± 0,154 points. The influence of the month of the year on sperm activity was 6,36 %. Thus, the best indicators of sperm production of bulls were established in the summer period; despite the decrease in the volume of ejaculates in bulls of all studied breeds, the high sperm concentration and activity allowed to reduce the marriage of native seed and increase the number of frozen sperm doses.