Tolerance of imported rabbits grown as meat animals to hot climate and saline drinking water in the subtropical environment of Egypt

Ninety of each of New Zealand White ( NZW) and Californian (Cal) male weaned rabbits at 5 weeks of age with nearly similar average live weights were used during two periods of the year ( mild and hot, each of 9 weeks), in a trial to evaluate their adaptability as meat animals to the subtropical conditions of Egypt. The results showed that NZW surpassed Cal, in most of the traits studied. The increase was significant in final live weight, daily weight gain,final body solids, daily body solids gain, body water concentration ( ml per 100 g body solids) and pre-slaughter weight. Meanwhile, Cal significantly surpassed NZW in daily water consumption. The temperature-humidity index (THI) values indicated absence of heat stress in the first period and exposure to moderate ( but very close to severe) heat stress in the second. The hot conditions induced significant decline in final live weight, daily weight gain, food intake,final body solids, daily body solids gain, plasma tri-iodothyronine (T3) hormone, total proteins, albumin, globulin, total lipids, glucose, electrolytes (Na, K, Ca, Mg and P), pre-slaughter weight and kidneys with fat weight. In contrast, the hot conditions were accompanied by significant increases in water intake, body water concentration, plasma urea-N, creatinine and physiological body reactions ( respiration rate and temperatures of rectum, skin and ear). Drinking water containing high levels of salt ( 3000 p. p. m. and more) caused significant decreases in final live weight, daily live-weight gain,final body solids, daily body solids gain, plasma T3 hormone, total proteins, albumin, total lipids, glucose, pre-slaughter weight and kidneys with fat weight. At the same time, significant increases occurred in water consumption, body water concentration, plasma urea-N, creatinine, electrolytes ( Na, K, Ca and P), respiration rate and rectal and skin temperatures. Estimations of adaptability to the subtropical environment of Egypt and tolerance to drinking saline water under the same conditions were found to be proportionately 0.844 and 0.876 and 0.821 and 0.803, in NZW and Cal, respectively.