Relationship between levels of peripheral blood testosterone, sexual behavior, scrotal circumference and seminal parameters in crossbred rams

ABSTRACT

Background: Measurements of testosterone, scrotal circumference and libido have a great value as indicators of onset of puberty, total semen production, semen quality, control of spermatogenesis, testicular state, pathological conditions of testes and the potential sub-fertility or infertility. Therefore, the aim of this study was to determine relationship between levels of peripheral blood testosterone, sexual behavior, scrotal circumference and seminal parameters in crossbred rams. Materials, Methods & Results: Twelve crossbred and sexually mature rams consisting of three Arkharmerino × Moghani (AM × MG), three Baluchi × Moghani (BL × MG), and three Ghezel × Baluchi (GH × BL) and three Ghezel × Arkharmerino (GH × AM) were used in this study. The scrotal circumference (SC) was measured at monthly intervals. Every two weeks the 12 crossbred rams were evaluated for the degree of libido using three ovariectomized ewes. Sexual behavior of crossbred rams was evaluated in terms of (1) reaction time for the first and second ejaculate (2) time taken for the first and second ejaculate (3) number of mounts for the first and second ejaculation. Ram semen was collected by artificial vagina and blood samples were obtained via jugular vein. Soon after the collection, semen characteristics and testosterone plasma were assayed. For estimation of the relationship between genetic group and other indices, Statistical analyses were performed by One-way ANOVA and Bivariate correlation coefficient was used to calculate the correlations between testosterone by spermatozoa parameters and libido in each genetic group; P < 0.05 considered significant. The results showed that there were no significant differences between crossbred rams in terms of semen characteristics except for spermatozoa progressive motility, semen volume and pH. The highest level of plasma testosterone was recorded in GH × BL rams (7.12 ± 1.87 ng/mL) and the lowest was for AM × MG genetic group (2.99 ± 1.90 ng/mL). However, any significant difference wasn't observed among the four genetic groups about plasma testosterone. At the present study the mean values of scrotal circumference of Arkharmerino × Moghani were higher than other genetic groups (P < 0.05). Also scrotal circumference showed a positive correlation with reaction time for the second ejaculation, semen pH and spermatozoa concentration (P < 0.05). Discussion: The sexual activity of males is influenced by test conditions and the methods applied in tests can vary considerably, even within the same experiment for example with regard to test duration and number of males and females. Among libido indices, only a significant correlation was observed between reaction time for second ejaculate and scrotal circumference. A non-significant correlation was observed between plasma testosterone, concentration, and semen traits. These differences between various reports could be due to the season of the study, breed, age of rams and many other environmental factors. It could be concluded that testosterone profiles is not a notable factor for estimating the quality of crossbred rams spermatogenesis and sexual activity. In addition to the above points, the males should be examined for a number of different tests have been used to assess the fertility or performance of crossbred rams, including scrotal measurement, semen examination, libido testing, hormonal profile and the other examinations.