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To determine the aflatoxin effect on performance, and humoral and mucosal immunity, 240 one-day old chicks were divided into 4 equal groups. Treatment groups include Group 1: chickens that received a standard diet based on corn and soy as negative control, Group 2: chickens fed with a basal diet containing 3 ppm aflatoxin as positive control, Group 3: chickens fed with 0.25% Mycoad® in basal diet, and Group 4: chickens fed with diet containing 0.25% Mycoad® plus 3 ppm aflatoxin. All chickens continuously received diets from hatching until 28 days old. Growth indices, such as weight gain, feed consumption and food conversion rate, were determined weekly. At 28 days, all chickens were sacrificed. After blood sampling, serum was prepared to measure serum IgG titer against Newcastle disease vaccine using the HI method. Moreover, the heads were collected for nasaltracheal lavage for assaying IgA against infectious bronchitis vaccine in the mucosa of the respiratory tract. The measurement of mucosal IgA was carried out using the ELISA method with specific goat anti-chicken IgA. That results indicated that chickens that received aflatoxin demonstrated lower growth indices, and fewer serum IgG and mucosal IgA titers than others did, while performance and immune responses in chickens that received Mycoad® plus aflatoxin were significantly higher than chickens fed with aflatoxin alone. Overall, it seems that aflatoxin can affect mucosal immunity in the upper respiratory tract as well as performance and humoral immune responses. Supplementation of Mycoad® to diet contaminated with aflatoxin can reduce the adverse effects of aflatoxin on performance, as well as mucosal and systemic immune responses. Key words: aflatoxin; chicken; immunity; Mycoad® VPLIV DODATKA MYCOAD® NA PRIRAST IN IMUNSKO ODPORNOST PIŠČANCEV Z AFLATOKSIKOZO Da bi preučili vpliv aflatoksina na prirast in imunski odziv (sistemski in v sluznicah) piščancev, smo 240 enodnevnih piščancev razdelili na 4 enake skupine in jih od izvalitve do 28. dneva starosti hranili s 4 različnimi krmami. Skupina 1 je predstavljala negativno kontrolo (piščanci, krmljeni s standardno krmo na osnovi koruze in soje), skupina 2 je bila pozitivna kontrola (piščanci, krmljeni s standardno krmo, ki je vsebovala 3 ppm aflatoksina), v skupini 3 so bili piščanci, krmljeni s standardno krmo z dodatkom 0,25 % Mycoad®-a, v skupini 4 pa piščanci, krmljeni s krmo, ki je vsebovala 3 ppm aflatoksina in 0,25 % Mycoad®-a plus. Tedensko smo določali različne pokazatelje rasti, kot so povečanje telesne mase, poraba krme in njen izkoristek. Po 28 dneh smo vse živali žrtvovali. Z uporabo metode HI smo v serumu določili titer protiteles IgG proti virusu bolezni Newcastle ter v izpirku nosu in sapnika določili titer protiteles IgG proti cepivu kužnega bronhitisa. Izmerili smo tudi raven sluzničnih protiteles IgA z metodo ELISA s specifičnimi kozjimi protitelesi proti piščančjim protitelesom IgA. Rezultati so pokazali, da imajo piščanci, ki so prejeli aflatoksin, nižje indekse rasti in nižje titre tako serumskih protiteles IgG kot tudi sluzničnih protiteles IgA. Medtem pa sta bila prirast in imunski odziv pri piščancih, ki so prejeli poleg aflatoksina tudi Mycoad® plus, bistveno višja kot pri piščancih, krmljenih samo z aflatoksinom. Naši rezultati kažejo, da vsebnost aflatoksina v krmi piščancev vpliva na lokalni imunski odziv sluznic zgornjih dihalnih poti in na učinkovitost sistemskega imunskega odziva. Dodatek Mycoad® h krmi, onesnaženi z aflatoksini, lahko zmanjša neželene učinke aflatoksina na uspešnost cepljenj pri piščancih. Ključne besede: aflatoksin; piščanci; imunost; Mycoad®