The evaluation of vitamin C effect on mucosal and humoral immune responses in broilers, in acute heat stress

In this study, 180 chicks were divided into 4 groups in two distinct houses and chickens were reared until 22 days old in normal condition. From 22 to 42 days old, chickens in group 1 and 2 (in house 1) were reared in normal condition and chickens in group 3 and 4 (in house 2) were reared in 35 ?C for 8 hours daily. Chickens in group 1 and 2 received vitamin C (100 mg/lit) from 22-42 days old. All chickens received ND and IB vaccines according to the routine vaccination program. Blood samples were prepared at 42 days old for determination of heterophil to lymphocyte (H:L) ratio and assaying of serum IgG against ND vaccine. All chickens slaughtered at 42 days old. The trachea and nasal lavages were used for assaying of mucosal IgA against IB vaccine. The IgA assay was done by Elisa and specific IB antiglobulin. Results showed that acute heat stress can decrease weight gain, feed intake, serum HI titer, mucosal IgA titer, and increase H:L and Feed conversion rate (FCR). Supplement of vitamin C to drinking water in chickens reared under heat stress can increase weight gain, feed intake, serum HI titer, mucosal IgA titer and decrease H:L ratio and FCR. The present study demonstrated that acute heat stress had negative effects on humoral and mucosal immune responses against respiratory vaccines and administration of vitamin C provided a useful effect on mucosal and humoral immune response in chickens reared under heat stress.