Stepwise regression analysis to assess various factors affecting on fresh sperm quality in Ouled Djellal ram

Abstract

The aim of this study was to evaluate the effect of various factors on fresh semen quality in Ouled Djellal rams. Specifically, we examined the impact of semen collection method, season, ram age, testosterone levels, body weight , and testicular weight. Twelve mature Ouled Djellal rams were used in the trial. Six rams were trained for semen collection using an artificial vagina (AV), while semen from the other six rams was collected using an electroejaculator (EE) biweekly throughout the year. Stepwise regression analysis showed that 62.50% of the variation in sperm volume, 48.60% of the variation in mass motility, 62.70% of the variation in sperm concentration, and 44.20% of the variation in total sperm count can be attributed to the collection method. Overall, significantly better semen quality was recorded for the artificial vagina (AV) collection method compared to the electroejaculator (EE) method. Of the seven variables studied, two factors—method of collection and season—had a significant effect on pH and the percentage of live sperm, accounting for 41.90% and 37% of the variation, respectively. Season was the most important predictor for the percentage of abnormal sperm, characterized by the equation PSA = 0.532 + 1.058 × season, with a correlation coefficient (R) of 0.459. In conclusion, Ouled Djellal rams responded better to AV than to EE for semen collection. Both the collection method and the season were significant factors influencing semen characteristics and can be used as key indicators for selecting superior breeding rams to enhance herd productivity.