Abstract
Abstract Objective: The aim of the experiment was to evaluate the effect of heat stress on body weight, immune response and cecal bacterial count in parent broiler chickens and to determine the ameliorating effects of some organic acids to overcome heat stress. Materials and Methods: Day-old, 1920 male broiler parent chicks were used in a 2×2 factorial completely randomized design. The experimental chicks were randomly and equally distributed into 2 major groups (960 chicks each) which further divided into 4 subgroups (480 chicks each) with 8 replicates. Two subgroups were exposed to heat (H) at 35EC from 22-42 days of age and the other two subgroups was lift normal. Four replicates in each subgroup were given organic acids (OA) in drinking water at the first week, days 19-27 and last week of age whereas the other 4 replicates in the same subgroup were given normal drinking water. Results: Heat stress caused significant decrease in body weight, coliforms count and serum lysozyme level at 5th week of age. The body weight has been significantly ameliorated by organic acids. Deleterious effects of heat stress on immunity has been confirmed by the significant decrease of bursa/body weight ratio and total leukocyte count (TLC) at 4th week of age. The bacterial count was significantly increased in the group exposed to heat at 5th week of age. Conclusion: It is concluded that heat stress has deleterious effects on chickens and organic acids has significantly ameliorated some of these effects. arabic 18 English 91