Sexual activity and sperm production of Charolais and Ile-de-France rams in different seasons of the year

Sheep ( Ovis aries ) are polyestrous animals with a distinct breeding season. Long artificial selection has minimized the impact of seasonal environmental factors on the sheep reproductive function. The seasonality of reproduction is practically not characteristic of sheep bred near the equator but is well pronounced in the middle and high latitudes. The basic strategy of sheep breeding in Russia is production of young mutton and lamb. As Russia does not have its own gene pool of highly productive specialized meat breeds, the use of the best alien breeds is inevitable. However, experimental data on the reproductive performance of alien meat rams under the conditions of the Central zone of the Stavropol territory is practically absent. Our study aimed to examine sexual activity and sperm production in meat sheep in different seasons in the Central zone of the Stavropol territory. During the breeding (autumn) and non-breeding (winter, spring, and summer) seasons, sperm samples were taken from Charolais rams ( n = 8) and Ile-de-France rams ( n = 5) using an artificial vagina. The rams of both breeds showed significant seasonal variation in their sexual activity and sperm production. In winter, the sexual activity of the rams decreased and the time required for the expression of the entire complex of sexual reflexes increased. Compared to autumn, the time of receiving ejaculate from Charolais sheep increased 1.70 times in winter, 2.56 times in spring, and 2.62 times in summer. The Ile-de-France rams showed similar dynamics, but a decrease in sexual activity was less pronounced compared to the Charolais rams. Ile-de-France rams took longer to ejaculate (1.09 times in winter, 1.62 times in spring, and 1.78 times in summer compared to breeding season). Sperm motility in Charolais rams varied from 9.1 points in breeding season to 7.4 points in spring. In winter and summer, the motility was 8.5 and 8.1 points, respectively. The volume of ejaculate and sperm cell concentrations showed similar patterns, being the highest in autumn, the lowest in spring, and intermediate in summer and winter. In autumn, Ile-de-France rams produced the largest volume of ejaculate with maximum concentration and the highest motility of sperm cells, i.e., 1.15 ml, 3.75 billion/ml, 8.57 points vs. 0.98 ml, 3.38 billion/ml, 7.95 points in winter, 0.88 ml, 2.85 billion/ml, 7.55 points in spring, and 0.96 ml, 3.15 billion/ml, 8.19 points in summer. Microstructural analysis detected sperm cells with an intact acrosome ranging from 65 % in summer in Charolais rams to 82 % in autumn in Ile-de-France rams. Therefore, despite significant seasonal variations, Charolais and Ile-de-France rams can produce high-quality semen both in breeding and non-breeding seasons under the climatic conditions of the Central zone of the Stavropol territory.