Effect of Chronic Heat Stress and Long-Term Feed Restriction on Broiler Performance Int

Abstract: An experiment was conducted to investigate the effects of long-term feed restriction on alleviating the effects of chronic heat stress on the performance of 4-8-wk old ISA Vedette broiler birds. Environmental temperatures were constant 25, and 35±2 C in controlled environmental rooms and variable-naturalo temperature ranged between 21 and 30±2 C in an open-sided poultry house. At 4 weeks of age, Daily feedo consumption in all experimental rooms was restricted to 75 % and 50 % of the daily ad libitum consumption recommended in the management guide for this strain. At the end of experiment, a representative sample of 8-wk-old broilers from each treatment was selected and placed randomly in controlled-environmental chambers set at 40±1 C for heat tolerance test. The results showed that, rearing temperature of 35±2 C ino o closed environment and variable-natural temperature of 21-30 ± 2 C in the open-sided environment had ao significant (p<0.05) negatively effects on broiler performance. Long-term feed restriction to 75 % or 50% reduced significantly (p<0.05) the growth rate and body gain of 4-8-wk old broilers. The body weight gain of birds reared at 35 C and fed 50 % of ad libitum was higher than their counterparts reared at constant 25 Co o or variable-natural temperature (21-30 C). Feed conversion ratio and survivability were significantly (p< 0.05)o improved with increasing feed restriction at high ambient temperature of 35 ± C. However, feed restrictiono at lower ambient temperature of 25 C had negative effects on feed conversion ratio. On the other hand, heat