Dose-dependent Effect of T-2 Toxin on the Immunity against Newcastle Disease Virus in Chickens

haemagglutination inhibition titres against Newcastle disease virus was investigated in broiler chickens. The animals were divided into four groups and two separate experiments were carried out (a, b): (1) intact control group; (2) birds were fed with T-2 toxin contaminated feed and not vaccinated; (3) repeatedly vaccinated (on day 23 of age) control group which received uncontaminated feed; (4) birds were both repeatedly vaccinated and fed the T-2 toxin contaminated diet. Blood samples, from which sera titres were measured, were taken on days 7 and 14 of the experiments. It was found that heamagglutination titres were different in the two experiments even in the control (1) group because of the different efficiency of the first immunization at the hatchery. Titres on day 7 showed increases in all groups except for the group fed lower T-2 contaminated diet (a, group 2) but during the second week they increased only in the groups fed the diet with a lower dose of T-2 toxin. On the contrary, a higher dose of T-2 toxin contamination of the diet resulted in a dramatic decrease during the second week (b, groups 2 and 4). The results suggested that contrary to most of the previously published data, feeding of T-2 toxin contaminated feed with an amount of 2.35 mg.kg-1 did not decrease, but increase the antibody formation against attenuated Newcastle disease virus even without a second vaccination on day 1 of the experiment, wherea