EFFECT OF EARLY HEAT STRESS ON THE PRODUCTIVE PERFORMANCE AND PHYSIOLOGICAL RESPONSE IN SOME LOCAL CHICKEN STRAINS

This experiment was conducted to study the effect of heat stress at early age on heat shock proteins, plasma Triiodothyronine (T3), thermal reaction, productive performance, egg quality, and immune response of Matrouh and Inshas chicks. Seven hundred and twenty, one day old chicks (360 Matrouh chicks and 360 Inshas chicks) were used in this study. Birds from each strain were divided into three groups. The first was not treate and kebt as acontrol group (T1), the birds in the second group were exposed to (42°C-43°C ±1°C) for 4 hrs at three days of age (T2) while birds of the third group were exposed to the same thermal treatment of the second group but at four weeks of age (T3). After these treatments birds of (T1 , T2 and T3) were raised under regular conditions. At 18 weeks of age 90 chicks from each strain (30 birds from each group) were subjected to heat stress (42°C-43°±1°C) for 4 hrs. Blood samples were taken from (5 chicks) before and after this heat stress. At 18 wks of age 5 birds from each treatment group were slaughtered. Blood samples were taken just prior and after heat exposure for analysis. Rectal temperature (RT) and respiration rate (RR) were measured before and after exposure to heat stress. Samples of liver (1g) were frozen in liquid nitrogen for further analysis. The second period of experimental was from sexual maturity till 6 months, on the same birds from previous two strains to study the effect of heat stress on egg quality. The important results obtained were: 1- Early heat conditioning birds showed increase on the expression of heat shock proteins (70 and 90). 2- Early heat exposure birds had the lowest plasma T3 content compared to control and (T3). 3- Early heat exposure birds had significant higher antibody titer against SRBC’s than control. 4- Results show that body weights were the highest in early heat exposed groups only in the Matrouh strain. 5- Early heat exposure caused lower rectal temperature and respiration rate in both strains. 6- Heat stress caused an insignificant increase in plasma total protein, albumin and globulin than that of control birds. 7- Heat stress at early age (3-day) improved in some parameters of egg quality and egg weight. Therefore heat stress at early age can improve thermotolerance at maturity then improve in the performance of bird.