Sexual Behaviour, Testosterone Concentration, Semen Characteristics and Testes Size of Ossimi Rams as Affected by Age and Scrotal Circumference

The objective of this study was to determine size of testes, sexual behaviour, semen quality and testosterone concentration on 40 Ossimi rams in relation to scrotal circumference and age. Rams were divided into two groups similar in age and body weight. Group A with age of 1-1.5 years old and group B with 2-2.5 years old. Each group was divided into subgroups according to the scrotal circumference (≤ 25 cm and > 25 cm) at the beginning of the study. Pre-copulation behaviour, body weight and testicular measurements for each ram were recorded weekly for one month before starting the experiment. Semen was collected to define its characteristics in addition to collect blood samples to determine testosterone concentration in the peripheral blood before copulation and after ejaculation. Results revealed that there were significant differences in body weight, number of mounting, testicular measurements, semen characteristics and testosterone concentration between rams under two age groups. In contrast, there were no significant differences in reaction time and pre-copulation behaviour. Rams had scrotal circumference > 25 cm showed stronger sexual behavior, testosterone concentration and semen characteristics (P<0.001) compared to rams had scrotal circumference ≤ 25 cm. There were positive correlations between number of mounting, scrotal circumference and testosterone concentration. On the other hand, there were negative correlations between reaction time and each of number of mounting, scrotal circumference and testosterone concentration. It could be concluded that the sexual activity and semen characteristics improved with age progress and increasing of scrotal circumference.