الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
Abstract
This experiment was carried out at the Farm of Poultry Breeding, Department of Poultry Production, Faculty of Agriculture, Ain Shams University. This research designed to study the effect of post-hatch heat exposure under environmental conditions of Egypt on some productive performance and immune response of three broiler strains (Cobb, Arbor Acres and Hubbard). Some measurements taken to measuring the productive performance such as (body weight – body weight gain – carcass characteristics), some blood parameters immune response traits such as (body lymphoid organs percentage - PHA-P injection ”In vivo cell-mediated immunity assay” - Antibody response against SRBCs).
The main results could summarize as follows:
• Productive performance
1- Body weight and body weight gain
Cobb strain showed the best body weight during most ages for control and heat exposed group. Live body weight gain for Cobb broiler strain recorded heights values compared to Arbor Acres and Hubbard strains for cumulative body weight gain during the five weeks of age.
2- Feed intake and conversion
The present result showed that the Cobb broiler chicks were significantly consumed more feed from 14 to 28 days of age compared to Arbor Acres chicks, while Hubbard chicks were intermediate. from 28 to 42 days of age, it could be noticed that the Cobb broiler chicks were significantly consumed less feed compared to the remaining strains. The mean feed consumptions of Cobb for mentioned experimental period (14-42 day) were only 96.2, 92.9 and 94.2% of that consumed by Arbor Acers, Hubbard broiler chicks respectively.
3- Carcass measurements
Cobb strain showed the best carcass characteristics under heat stress conditions.
4- Mortality Rate
Arbor Acres strain for each group (control and treated) have the highest viability.
5- Blood Parameters
Cobb broiler chicks had significantly highest plasma total protein compared to Arbor Acers broiler chicks. However, the Hubbard broiler chicks were intermediate. There was no significant difference among strains for plasma albumin. Conversely, there was a significant difference among strains for plasma globulin, whereas the Cobb broiler chicks had significantly highest for plasma globulin compared to Arbor Acers and Hubbard broiler chicks.
6- Rectal temperature and respiration rate
Arbor Acres considered the best strain which did not effected a lot such another strains with heat exposure.
7- Lymphoid organs weight
The control group and Hubbard strain showed an increase in bursa weight compared to heat exposed group and another strains, subsequently.
8- Cell mediated immunity
No significantly of cell mediated in groups among all strains. A significant increase recorded in the second differentiation of Cobb strain among other strains.