Semen quality parameters as fertility predictors of water buffalo bull spermatozoa during low-breeding season

The present study was carried out to assess various postthaw semen quality parameters for the prediction of fertility in buffalo bull during low-breeding season. Semen (30 ejaculates) was collected from five adult buffalo bulls with artificial vagina (42 °C). Sperm motility parameters, velocity distribution, motion kinematics, and subpopulations were analyzed by computer-aided sperm motion analyzer (CASA). Moreover, sperm visual motility, supravital plasma membrane integrity, viability/acrosome integrity, viability/mitochondrial transmembrane potential, DNA fragmentation/integrity, and morphology were analyzed by phase-contrast microscope, supravital hypoosmotic swelling test, Trypan blue/Giemsa staining, propidium iodide/“5,5′,6,6'-tetrachloro-1,1′,3,3'-tetraethylbenzimidazolyl carbocyanine iodide” (JC–1) fluorochromes, neutral comet assay/acridine orange assay and wet mount technique, respectively. Outcome of 528 inseminations was analyzed for in vivo fertility. Pearson's correlation coefficients revealed that sperm progressive motility (%), rapid velocity (%), average path velocity (μm/s), straight line velocity (μm/s), subpopulation one (most rapid, and progressive) of motile spermatozoa (%), supravital plasma membrane integrity (%), and viable spermatozoa with intact acrosome (%) were significantly correlated with in vivo fertility (r = 0.64, P < 0.01; r = 0.57, P < 0.01; r = 0.52, P < 0.01; r = 0.56, P < 0.01; r = 0.73, P < 0.001; r = 0.74, P < 0.001; r = 0.88, P < 0.001); whereas nonviable spermatozoa with damaged acrosome or low-mitochondrial transmembrane potential and comet length (μm) of neutral comet assay were negatively associated with in vivo fertility (r = −0.79, r = −0.75, P < 0.001, and r = −0.60, P < 0.05, respectively). Multiple regression analysis reported that combination of semen quality parameters as predictor of fertility were better (R2 adjusted = 81.30%, P < 0.001) as compared with single parameter (R2 adjusted = 50.20%, P < 0.007). It is concluded that assessment of CASA parameters and some other sperm structural and functional parameters, that is, integrity of plasma membrane and acrosome, and transmembrane potential of mitochondria were able to predict the in vivo fertility of water buffalo bull during low-breeding season.