Association of <scp>CASA</scp> ‐Derived Semen Parameters With Conception Rate in Murrah Bulls

The present study investigated the relationship between seminal parameters and bull conception rate (BCR) in 72 Murrah bulls using Computer-Assisted Sperm Analysis (CASA). The BCR was calculated by obtaining data of artificial insemination spanned over two decades from buffalo farms of two organised herds of India. The association of seminal parameters and BCR was studied using multiple regression and principal component analysis. The average BCR was 38.95% ± 1.51%, ranging from 22.50% to 80.51%. Total motility (TM), progressive motility (PM), average path velocity (VAP), straight line velocity (VSL), curvilinear velocity (VCL), and amplitude of lateral head displacement (ALH) showed significant positive correlations with BCR, whereas straightness (STR) and linearity (LIN) were negatively correlated. Multiple regression (R² = 0.29) identified TM as the most reliable predictor of BCR. Principal component analysis (PCA) extracted three components, PC1 (Sperm velocity and head movement, 54.36% variance), PC2 (Trajectory and beat frequency, 19.56%), and PC3 (Progressive motility and path accuracy, 12.98%), explaining 86.90% of the total variance. Regression using PC scores (R² = 0.24) indicated positive effects of PC1 and PC3, and a negative effect of PC2 on fertility. Overall, sperm velocity and progressive motility were primary fertility determinants, while excessive linearity hindered conception success. Therefore, association of seminal parameters with BCR can be explored for enhancing breeding efficiency of bulls. Future breeding programmes should prioritise sperm velocity and progressive motility traits while avoiding excessive linearity to improve bull fertility and conception success.