Comparative Semen Evaluation of Malpura and Bharat Merino Rams by Computer-aided Sperm Analysis Technique Under Semi-Arid Tropical Environment

The present study was conducted to compare sperm motion characteristics of adult Malpura and Bharat Merino rams by the computer-aided sperm analysis (CASA) technique. Malpura is a hardy native sheep breed of the semi-arid tropical environment and Bharat Merino is a crossbred evolved in the same environment by crossing native sheep with exotic rams. Semen was collected from 8 donor rams of each breed at the onset of autumn season on 5 occasions at three days interval. The data were analyzed by analysis of variance using the general linear model repeated measures procedure. The CASA parameters which differed significantly (p<0.05) between the breeds were rapid motile sperm, medium motile sperm, slow motile sperm, linearity, straightness, curvilinear velocity, average path velocity, straight-line velocity, amplitude of lateral head displacement, beat frequency, sperm head area and sperm head elongation with higher values in all traits in Malpura breed. The semen volume and sperm concentration were higher in Bharat Merino breed but the differences were not significant. The body weight of rams had significant (p<0.05) effect on mass motility, curvilinear velocity and amplitude of lateral head displacement. The mass motility was higher in rams of more than 50 kg body weight while curvilinear velocity and amplitude of lateral head displacement was higher in rams of less than 50 kg body weight. A significant (p<0.05) influence of age of rams was observed on linearity and amplitude of lateral head displacement. The linearity was higher in rams of less than 3.5 years of age whereas amplitude of lateral head displacement was higher in rams of more than 3.5 years of age. In conclusion, CASA derived sperm motion characteristics revealed that the semen quality of native Malpura rams was better compared to crossbred Bharat Merino rams during major breeding season in a semi-arid tropical climate.