In the present study, effects of stress-free and stressful seasons on certain physical and biochemical attributes of semen of Cholistani AI bulls were investigated. A total of 382 ejaculates from six bulls were collected at weekly intervals during four seasons viz. stress-free autumn (October-November), stressful winter (December-January), stressful dry summer (May-June) and stressful wet summer (July-August). These ejaculates were evaluated for various physical and biochemical attributes. Overall mean values (±SEM) for ejaculatory volume, number of ejaculates per bull, mass motility, individual sperm motility, sperm concentration, number of doses of semen frozen per bull, percentages of live, morphologically normal sperm and those with intact acrosome were 4.92±0.14 mL, 1.89±0.02, 2.26±0.06, 63.51±1.03%, 989.73±27.4 million/mL, 208.26±8.42, 86.74±0.55%, 86.34±0.51% and 86.64±0.48%, respectively. In general, all the parameters revealed significantly (P<0.05) better results in stressful seasons as compared to stress-free season. Overall mean values for Na⁺, K⁺, cholesterol and glucose in the seminal plasma were 102.79±3.95 & 36.65±0.99 mEq/L, 152.02±3.17 & 127.22±3.65 mg/dL, respectively. Amongst these, Na⁺ was higher (P<0.05) during dry summer, whereas K+ was higher in dry summer and winter. Cholesterol and glucose were elevated (P<0.05) during dry summer season. Correlation analysis revealed significant positive correlations between mass and individual sperm motility, morphologically normal and live sperm and sperm acrosome integrity and live sperm (P<0.01). Among biochemical attributes of seminal plasma, Na⁺ and K⁺, cholesterol and K⁺ and glucose and Na⁺ were correlated (P<0.01). Considering seminal plasma biochemical constituents and physical attributes, only seminal plasma cholesterol was positively correlated with ejaculatory volume (P<0.01). In conclusion, various physical and biochemical attributes of Cholistani bull semen were better in stressful seasons as compared to stress free season.

Key words: Cholistani bulls, Season, Seminal attributes, Stress-free, Stressful