EN
In two farms (A and B) losses of calves in the first 2—3 days after birth caused by diarhhoea were 25,2% and 36,5%. Bacteriological examinations of the intestines revealed an especially high concentration (2,4 X 10⁹ — 3,6 X 10¹⁰ cells/g) of the highly toxinogenic „in vitro” C. perfringens A. Contents of intestines were, however, free of lethal toxins. Examinations of pathological properties of C. perfringens A isolates showed that they produced strong alpha, theta and kappa toxins, and the majority of isolates additionally produced mi and ni toxins. Lack of toxins in the intestines may result from their quick binding with body tissues. This observation is confirmed by the high effectiveness of prophylatic measures i.e. immunization of animals against alpha toxin (article in preparation). The result point to the role of nonenterotoxinogenic strains of C. perfringens A, producing alpha toxin, in the etiology of diarrhoea of newborn calves.