This experiment was carried out at the rabbitry of the Experimental Farm, Faculty of Agriculture, Suez Canal
University, Ismailia, Egypt. Twenty four adult rabbit males were used in this study (12 New Zealand White (NZW) and
12 Californian (Cal) rabbit bucks) to study the effect of Vit C ingestion (20 mg/kg body weight/ day for 45 days) on
alleviating the effects of high housing temperature and improving semen quality parameters and some physiological
traits of rabbit bucks during summer season. Generally, summer heat adversely affected the physiological performance
of the two rabbit breed bucks. However, most of the studied traits were differed (P≤0.05) due to the breed effect. Cal
breed had lower (P≤0.05) rectal temperature (RT), and higher (P≤0.05) WBCs values than NZW. Thus, Cal breed had
lower (P≤0.05) reaction time and semen pH values than in NZW breed. Moreover, Cal breed had higher (P≤0.05)
ejaculate volume, percentage of live sperm and sperm output than NZW breed. Irrespective of breed of rabbits,
ingestion of Vit C improved (P≤0.05) most studied traits under summer conditions. Addition of Vit C decreased
(P≤0.05) RT, respiration rate (RR) and pulse rate (PR) and increased (P≤0.05) values of Hb value, Ht % and WBCs
counts compared to the control group during summer period. Furthermore, addition of Vit C decreased (P≤0.05)
reaction time and semen pH and increased (P≤0.05) ejaculate volume (with and without gel) and % of forward motility
of spermatozoa compared to the control group. Increased (P≤0.05) percentage of live sperm, sperm concentration and
sperm output and decreased (P≤0.05) percentage of sperm acrosome alteration and sperm abnormalities was observed in
Vit. C treated group compared to the control group. In conclusion this study sugessted that the Cal breed was more heat
tolerant and adapted to heat stress than NZW breed under Egyptian summer condition. Also, the addition of Vit C to
drinking water alleviated the stressful effects of high temperature on semen characteristics and physiological traits in
rabbit bucks during summer season.