الفهرس 
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Abstract
High ambient temperature is one of the most serious problems for
poultry production not occurring only in tropic countries but also,
occuring in subtropic countries including Egypt when high
temperature associated with high humidity and this is the main
cause of heat stress. This study was carried out to investigate the
effect of supplementation of ascorbic acid (AA), N-acetyle cysteine
(NAC) and their combination on some performance, hematological,
biochemical parameters and some antioxidant parameters in broilers
exposed to acute and chronic heat stress. Two hundred and fifty,
one –day- old Cobb broiler chicks of both sexes apparently healthy
were used in this study. Broilers at age of 35 days were randomly
divided equally into groups then exposed to both acute and chronic
heat stress.
Acute heat stress, One hundred and twenty five broiler chickens
were randomly subdivided to 5 equal groups (each of 25 birds)
Group 1: Broilers were kept as control (normal) at 22°C and 50-
60% relative humidity and non treated.
Group 2: Broilers were exposed to heat stress for 4 hours per day at
39± 0.5°C and 80-85% relative humidity for one day and non
treated (Acute heat stressed group).
Group 3: Broilers were exposed to heat stress as in gp.2 and given
a ration supplemented with 250 mg of L-ascorbic acid/ kg of
ration.
Group 4: Broilers were exposed to heat stress as in gp.2 and
supplemented with 100 mg N- acetyle -L- cysteine /kg of ration.