Evaluation of sexual behavior of Fars Grey rams in different seasons

ABSTRACT

To evaluate seasonal variation in sexual behavior of Fars Grey rams. Six healthy Fars Grey rams [3-4 years old]. Procedure All rams were exposed fortnightly to ewes and the following indices were evaluated 1] number of mounting 2] number of mating without ejaculate 3] number of ejaculation 4] reaction time. The test was carried out by exposing two rams to two ewes in a 20 minute period. Ram efficiency was calculated by dividing the number of ejaculation by the sum of number of mating with and without ejaculation. Blood samples were also collected immediately after each sexual behavior test to determine plasma testosterone concentrations. A commercial ELISA hormone assay kit was used to measure plasma testosterone concentrations. Chi-square test and GLM procedure in ANOVAofSAS.estosterone concentrations varied between 3.6 ng/ml in autumn to 10.3 ng/ml in summer [P<0.05]. A significant [P<0.05] seasonal effects was observed in the number of ejaculation in summer [0.9] and in winter [2.2]. Rams showed a significant individual variation in the number of ejaculations [P<0.05]. The highest number of mating without ejaculation was recorded in winter [7] whereas rams showed the lowest corresponding value in autumn [2.5]. Ram efficiency was varied among rams [P<0.05] and further a significant seasonal variation was observed in the ram efficiency [P<0.05]. There was a significant increase in the mean plasma testosterone concentrations in summer, particularly in late summer. The ram efficiency reached to the highest level in autumn, shortly after a decrease in plasma testosterone concentrations. Therefore, it can be concluded that the rise in ram efficiency is a delayed effect of the increase in mean plasma testosterone concentration. The results of this study also emphasize the need of evaluation of breeding rams for their sexual behavior prior to mating season. This is due to the individual variation that is observed among Fars Grey rams. An scoring system in the sexual behavior of breeding rams needs to be developed to make the test a useful tool in ram selection