Seasonal changes of scrotal circumference, blood plasma testosterone concentration and semen characteristics in Racka rams

Seasonal changes of scrotal circumference, blood plasma testosterone concentration and semen characteristics were studied over a period of 12 months in rams of the Hungarian Black Racka breed. Significant differences between seasonal averages of the parameters measured were established in multiple cases. As regards changes in scrotal circumference, the highest average value obtained in September (31.92 cm) exceeded the lowest value measured in January (22.08 cm) by 44.7%. It has been found that the season significantly affects the testicular dimensions (r = 0.87, P < 0.01). Significant correlations were found between scrotal circumference and day length (r = 0.43, P < 0.05) as well as between scrotal circumference and monthly average temperature (r = 0.73, P < 0.01). The lowest blood plasma testosterone (T) level (2.31 ± 0.14 ng/ml) was measured in winter and the highest in autumn (17.81 ± 0.7 ng/ml). Significant differences between the seasonal values were observed on multiple occasions. The GnRH-provoked maximal testosterone level (Tincr) was found in autumn, in the breeding season (54.02 ± 3.78 ng/ml). A significant correlation was found between T and Tincr on the one hand and scrotal circumference on the other (r = 0.62, P < 0.01 and r = 0.69, P < 0.01, respectively). Ejaculate volume tended to increase from spring (0.52 ± 0.03 ml) to autumn (0.88 ± 0.03 ml). The lowest sperm concentration (4.92 ± 0.13 × 109/ml) was measured in winter and the highest in summer (6.56 ± 0.21 × 109/ml) (P < 0.001). Total sperm count per ejaculate was the lowest in spring (3.15 ± 0.23 × 109/ml) and the highest in autumn (5.22 ± 0.45 × 109/ml) (P < 0.001). Sperm motility was at a low level in February (4.42 ± 0.20) and subsequently showed the highest values in the summer months, with similar monthly averages in June-August (5.00 ± 0.00, P < 0.001). The percentage of abnormal spermatozoa was the highest in winter (18.48 ± 3.23%) and the lowest in autumn (7.95 ± 1.58%) (P < 0.001), and it was significantly higher in February than in other months of the year (22.17 ± 1.61%, P < 0.001-P < 0.02). The lowest number of deformed spermatozoa was observed in October (6.15 ± 0.72%).