Seasonal changes in semen characteristics of pure and crossbred rabbit bucks fed graded levels of vitamin C under heat stress conditions

The experiment was carried out to investigate the effect of season and graded vitamin C levels on semen quality of rabbit bucks in the Northern Guinea Savanna of Nigeria. A total of 55 rabbit bucks consisting of 40 pure New Zealand White (NZW) and 15 New Zealand x California (NZW×CAL) crossbreds were used for the study. The duration of the study spanned the hot dry (March-May) and cool wet (June-August) seasons. The traits investigated were semen motility, concentration, volume, pH, colour, live and dead sperm. Results obtained showed that vitamin C had significant (p<0.01) effect on semen characteristics. There was a progressive increase in semen motility, concentration and live sperm and decrease in dead sperm as vitamin C level increased. Semen volume deviated from this pattern while colour was consistent all through. The result on monthly variation indicated that volume increased during the months of March to May ranging between 1.32-1.43 ml while during the months of June to August, it oscillated between 0.41 - 0.95 ml. Sperm concentration significantly (p<0.05) increased from the hot dry months (75.72-129.48x106) to the cool wet months (98.17-102.78x106) while colour remained consistent with an increase in live sperm cells. There was significant (p<0.001) interaction between vitamin C level and season on sperm motility, concentration and live sperm being better in the hot dry (70.9%, 114.5x106, 85.31%) and cool wet (76.3%, 121.6x106, 90.14%) seasons on 400 mg/kg feed vitamin C. Sperm volume was higher on 100 mg/kg feed vitamin C in the hot dry (1.60 ml) and cool wet (0.98 ml) seasons and 400 mg/kg feed in the hot dry (1.57 ml) and cool wet (0.77 ml) than other levels. Based on the results, it is concluded that vitamin C improved the semen characteristics of rabbit bucks at 400 mg/kg feed during the hot dry season which translates to improved semen quality.