THE IMPACT OF DIFFERENT SOURCES OF DIETARY UNSATURATED FATTY ACIDS OR FEED RESTRICTION ON PRODUCTIVE PERFORMANCE AND IMMUNOLOGICAL STATUS OF BROILER CHICKENS SUBJECTED TO HEAT STRESS

Abstract

High ambient temperature is one of the most important problems for poultry production in many regions of the world. Large economic losses occur because of mortality and decreased production under heat stress. At high ambient temperature, growth rate decreases as a result of reduced feed intake and increased respiratory rate causing respiratory alkalosis .Moreover, acute stress caused by sudden increases in temperature usually results in a large number of deaths. Heat stress causes behavioral, physiological and hormonal changes. High ambient temperature can also cause adverse effect on the structure and physiology of the cells such as impairment of transcription, RNA processing, and translation. Besides, intensive poultry production requires fast-growing strains usually at high stocking densities. With this type of husbandry, flocks are highly susceptible to infections agents, either as a result of reduce immune potential or as a result of deteriorating environmental hygiene. Consequently, in regions with seasonally high ambient temperature, heat stress is the major concern of the broiler industry because of resulting poor growth performance, immune suppression and high mortality. Furthermore, it is also known that exposure to high ambient temperature modifies various components of immune function such as T-cell count, natural killers cell count, lymphocytes proliferation and immunoglobulin concentration. The concept that nutrition influences immunity has been recognized for several decades, but it is only recently that role of individual nutrients in regulating immune function has been investigated. Moreover, the immune response of chickens has been shown to be influenced by number of nutrients: vitamins (A,C and E), selenium and methionine. Apart from their role in supplying calories, dietary fats are becoming recognized as important