Negative Effects of Heat Stress Conditions Dduring the Hot Summer Season in Egypt on Rabbits Productivity and Alleviation of These Effects Using Some Supplementary Nutrients

Optimal climatic conditions for rabbits would be something like an air temperature of 13 to 20 ºC, wind velocity of 5 to 18 km/hr, the relative humidity of 55 to 65% and a moderate level of sunshine and these factors are interrelated. Changes in these environmental factors cause heat stress on rabbits which the animal body has problems dissipating excess heat. In tropical and sub-Tropical countries like Egypt, the climatic characteristic is the major constraint on animal productivity. The summer in Egypt is characterized by high ambient temperature, intense solar radiation and high relative humidity. Therefore, rabbits will be exposed to such severe climatic stress for almost 6 months of the year. Exposure of rabbits to heat stress evokes a series of drastic changes in the biological functions, including a decrease in feed intake, feed efficiency and utilization, disturbances in water, protein, energy and mineral balances, enzymatic activities, hormonal secretions and blood metabolites ending to impairment the productive and reproductive performance. The process of minimizing or reducing these drastic changes in the biological functions in rabbits during the hot summer season is called the amelioration process. Amelioration of heat stress in heat-stressed animals to improve its productivity has been attempted using different techniques including some nutritional means. Vitamins A, D3 and E are potent antioxidants and rabbits cannot produce these vitamins in their bodies. Therefore an exogenous regular supply is needed to cover the physiological requirements and to sustain high production performance. Vitamin E and Selenim are involved with cellular antioxidant status and the existence of a synergistic action between selenium and vitamin E both improved synergistic antioxidant effect. Oxidative stress commonly occurs following heat stress in tropical regions and negatively affects on animals' performance. The antioxidant activity is high in medicinal plants and antioxidants play an important role in providing protection to animals against heat stress conditions. Ginger lowered lipid peroxidation by maintaining the activities of the antioxidant enzymes. Curcumin or Turmeric has a wide spectrum of biological actions including antioxidant effect due to it acts as a scavenger of oxygen free radicals and lowers the production of reactive oxygen species like superoxide anions, H2O2 and nitrite radical which increased when exposure rabbits to heat stress condition. The present work reviewed the effect of heat stress of hot summer season on the productive and reproductive performance of rabbits and using of different nutritional supplements for alleviating the negative effect of heat stress on rabbits during the hot summer season of Egypt.