I. Valchev, N. Grozeva, L. Lazarov, D. Kanakov, Ts. Hristov, R. Binev, Y. Nikolov

Abstract. The purpose of this study was to investigate the toxic effects of aflatoxin В (AFB ) on production traits (live body weight, weight gain, feed intake and 1 1 feed conversion) and relative weights (g/100 g body weight) of visceral organs (liver, kidneys, thymus, spleen, Bursa of Fabricius, heart, gizzard and proventriculus) in mulard ducklings. The experiment was carried out with four groups of 30 10-day-old ducklings each over 42 days. The groups were as followed: group І – control, which received standard feed according to the species and age, group ІІ – experimental, which received compound feed with 0.5 mg/kg AFB , group ІІI – receiving compound feed supplemented with 0.8 mg/kg AFB and group IV – compound feed supplemented with 0.5 mg/kg AFB and 2 1 1 1 g/kg Mycotox NG. In experimental groups II and III, the body weight, weight gain, feed intake were lower, feed conversion ratio was higher as well as the relative weights of liver, kidneys, heart, pancreas, gizzard and proventriculus. At the same time, the relative weight of the thymus, bursa of Fabricius and the spleen were considerably reduced. The supplementation of feed of group IV with Mycotox NG protected birds from the negative effects of AFB on production traits and 1 prevented changes in the weights of visceral organs.