اثر شوك حرارتي در مراحل اوليه رشد بر افزايش تحمل حرارتي و عملكرد طيور گوشتي

The effect of heat shock at early growth phase to improve thermotolerance and performance in broiler chickens

The aim of this study was to investigate the effect of induction of heat shock at early age to improve thermotolerance at advanced age in commercial broiler chickens. At the age of 1 day, 480 male broiler chickens (Arian breeds) were randomly distributed into four experimental groups (four treatments x six replicates) with 20 birds per replicates. The experiment was included four treatments; 1) an unexposed control group (Ti); 2) chickens exposed to 38 ±1°C at age of 3 and 4 day for 48 h (T2); 3 ) chickens exposed to 38±1°C at age of 4 and 6 days for 48 h (T3); and 4) chickens exposed to 38±l°C at age of 3, 4 and 6 days for 72 h (T4). At 1 week of age, the body weight gain of exposed chicks was significantly lower (p5 0.05) than unexposed control group while gradually in the following weeks compwastory growth were observed in T2, T3 and T4 groups. At the age of 42 days, the T2 and T4 groups showed significantly higher body weight gain and lower feed conversion rate than control group (p<0.05) Abdominal fat pads as percentage of body weight were significantly (P < 0.05) lower in all previously exposed treatment groups than in control group, Exposure to high temperature (38±1 °C) at day 42 for 4 h resulted in significantly lower mortality in the previously treatment groups than in the control group (P <0.01). The result of the present study showed that an early age temperature conditioning resulted in a significant improved thermotolerance, final performance and survival rate in broiler during the heat stress at advanced ages. From the practical point of view, this may be used as an efficient method for broiler raising in hot climate regions.