Performance of New Zealand White and Californian male weaned rabbits in the subtropical environment of Egypt

The New Zealand White (NZW) was superior significantly (P < 0.05) to the Californian (Cal) breed in final body weight, final total body solids and preslaughter weight. In contrast, Cal showed greater plasma creatinine (P < 0.001) than the NZW. The differences in the other traits were not significant. NZW also showed higher dressing percentage and Cal showed higher mortality percentage. The Temperature-humidity Index (THI) values indicated absence of heat stress in the first period (mild period) and exposure to moderate (very close to severe) heat stress in the second one (hot period). The heat stress conditions caused significant (P < 0.001, 0.01 or 0.05) decreases in each of final body weight, daily body gain, daily feed intake, final total body solids, solids daily gain, plasma total protein, albumin, globulin, total lipids, glucose, thyroid hormone T3, sodium, potassium, calcium, magnesium and phosphorus and preslaughter weight. At the same time, significant (P < 0.001 or 0.01) increases occurred in each of water intake, water/feed ratio, total body water (mL/100 g body solids), blood urea-N, creatinine, respiration rate and rectal, skin and ear temperatures. The interaction of breed x period effects was significant (P < 0.01 or 0.05) on plasma creatinine and hind-limb cut. Estimations of `adaptability' to the subtropical environment of Egypt were found to be 83.1\% for NZW and 82.6\% for Cal breeds.