EN
The studies were carried out in the North -West part of Poland. The investigation was conducted on 292 specimens of the Holstein cattle with added 50% of HF.The extensity and intensity of the coccidia infection were determined by means of the Willis-Schlaaf's and McMaster's methods. Six species of coccidia were found : E. bovis, E. auburnensis, E. zürni, E. ellipsoidalis, E. subspherica and E. cylindrica. Twenty seven per cent of dairy cows and 49.6 per cent of calves were infected . Number of oocysts per gram of feces in calves ranged form 333 to 2237. Observations on the dynamics of the coccidia invasion in calves during a yearly cycle exhibited the existence of two peaks; a vernal and an autumnal ones.