Histopathological changes of lymphoid system in broiler chicks after treatment with lactobacillus acidophils under heat stress

The study was conducted to investigate the effect of lactobacillus acidophilus on infected broiler chicks with E.coli. The study included 80 broiler chicks that are one day old which were divided into four equal groups (n=20). Group 1 one was given the lactobacillus acidophilus at one day old in dose of 1×10^8 CFU/0.1 orally while group 2 was given the same dose but at 21 day old. Group 3 was given the highly pathogenic E.coliat dose of 1×10^9CFU/ml at 35 day old and was regarded as the positive control. Group 4 was given the physiological saline solution and was regarded as the negative control. All three groups were exposed to heat stress, at the age of 31day old 50% of the total number were killed and the lymphoid tissue were extracted, these include: cecaltonsils, thymus gland and Harderain gland which were fixed in 10% neutral formalin. The remaining chicks were injected with E.coli in a dose of 1×10^9CFU/ml at the age of 35 days. All birds were scarified at the age of 38 days to investigate the lymphoid tissue and for their fixation in formalin. The result for the positive control showed that there were sloughing of the mucosal layer at the cecal tonsil in addition to heterophil infiltration of sub mucosa of Harderain gland and vacculation of epithelail cell lining of the Harderain gland, the thymus gland showed heavy lymphocytic infiltration in 2nd group while group 1 showed moderate hyperplasia of the lymphatic tissue. We concluded that lactobacillus acidophilus play an important role in the protection against E.coli infection under heat stress especially when they are given after the development of the immune system.