Effect of age and season on some semen parameters of Nili-Ravi buffalo (Bubalus bubalis) bulls

This study was carried out on 16 buffalo bulls (Bubalus bubalis) divided into four age groups, including three healthy (less than 5, 6-10, and more than 11 year old animals), and one abnormal group (6-10 year old bulls having poor semen quality). The study was undertaken for a one year period divided into five seasons (dry summer, humid summer, autumn, winter and spring). Overall semen volume was 4.67±1.62 ml and showed a nonsignificant difference between age groups, although it was higher (P<0.05) in autumn. Overall semen pH was 6.55±0.50 and was lower (P<0.05) in the 6-10 than in the 11 year old bulls and the abnormal group. It was lower (P<0.05) in autumn while higher (P<0.05) in winter. Colour score was higher (P<0.05) in less than 5 year old bulls. However, it was lower (P<0.05) in the abnormal group than in healthy groups but was lower (P<0.05) in dry summer. Overall mass activity score was 2.65±1.03 and was lower (P<0.05) in more than 11 year old bulls. However, it was lower (P<0.05) in the abnormal than in healthy groups. Mass activity score was higher (P<0.05) in dry summer and spring. Overall sperm motility was 56.89±0.65% and showed no difference in healthy groups, but was lower (P<0.05) in the abnormal group. It was lower (P<0.05) in winter than humid summer and autumn. Overall sperm concentration was 1.00±0.50 millions/ml and was higher (P<0.05) in less than 5 year old bulls. However, it was lower (P<0.05) in the abnormal group. Sperm concentration was lower (P<0.05) in winter. The pH of semen showed negative (P<0.001) correlation with colour (r=-0.38), sperm concentration (r=-0.37), mass activity (r=-0.37) and motility (r=0.17). Sperm concentration correlated positively (P<0.001) with mass activity (r=0.86) and progressive motility (r=0.16).