effect of milk thistle on the immune system, intestinal related variables, appearance and mortality of broilers contaminated with aflatoxin b1

background & aim: aflatoxin (af) is the most important fungus that contaminates food and feed and can enter the food chain of humans. the aim of this study was to investigate the ability of thistle seeds (silybum marianum l.) to reduce the adverse effects of aflatoxin b1 (afb1) on the immune system, variables related to the intestine, appearance and mortality of the broiler chickens. experimental: in this experiment, a total of 216 male ross 308 broiler chickens in a completely randomized factorial design 3 × 3 with nine treatments, four replications, and six chickens unit were grown on the ground for 35 days. treatments was included three levels of afb1 (0, 250, and 500 ppb) and three levels of milk thistle seed (0, 0.5 and 1%). influenza and newcastle diseases virus (idv & ndv) titers in two steps (25 and 34 days), variables related to the intestine at the end of the experiment along with the weekly appearance and mortality of broiler chickens were evaluated. results & discussion: analysis of idv and ndv results in the day 34 showed a reduction in titers of them in birds receiving diets contaminated with 500 ppb afb1 (p ≤ 0.05). also, the length of the ileum and the total intestine at the end of the experimental period (day 35) indicated decrease in the group of birds received diets containing 500 ppb afb1 (p ≤ 0.05).  chicks receiving diet containing 500 ppb of afb1 had the most of feather abnormalities, aggressive behavior and minimal body size compared with other treatments. mortality due to afb1 consumption in various experimental treatments was not significant. recommended applications-industries: probably phitosomes of milk thistle seeds (mts) reduce the mortality rate, nervous and aggressive behavior and increase the immunity of broilers against idv & ndv in afb1 exposure time.