This study was conducted at the field of poultry-Abu Gharib/department of Animal Production/college of agricultural engineering Sciences-university of Baghdad, during the period from 12/10/2019 to 24/11/2019 duration (42 days), to demonstrate the effect of adding different levels of Allicin to broiler diet on Glutathione level in blood and histological of thymus gland, total of 225 Ross 308 chicks was used. Birds were randomly distributed into five treatment groups which were: First treatment T1: without additives to diet (control), other treatments T2, T3, T4, T5 was added Allicin at a rate of (800,600,400,200 mg/Kg diet) respectively, and Allicin was added from first day until the end of the experiment for all addition treatments, results of this experiment showed: High significant (P< 0.01) in all additive treatments compared to control for glutathione enzyme in plasma at 21, 42 days for broiler age. With respect to the histological examination of thymus gland showed that adrenocortical hyper function and degeneration and depletion in lymphoid tissue in T2, T3 and T5 treatments compared to control treatment, while cortex and Pulp with a lymphatic interstitial in the stage of degeneration for T4 and control treatments.
