AN OBSERVATIONAL STUDY OF EIMERIA SPECIES IN HOUSED CATTLE ON DUTCH DAIRY FARMS

The prevalence of oocysts of Eimeria species in calves (n = 334), year lings (n = 254) and cows (n = 1314) was determined on 38 Dutch dairy f arms. Twelve species of Eimeria were identified in faecal specimens by sucrose-flotation. The prevalences of Eimeria spp. differed markedly in the different age classes on individual farms as well as between fa rms. The overall prevalence of Eimeria oocysts in faecal specimens was 46% for calves, 43% for yearlings and 16% for cows. The number of ooc ysts excreted was generally low in cows and yearlings, whereas high nu mbers of oocysts per gram of faeces (OPG) were exclusively observed in calves. No cases of clinical coccidiosis were observed in this survey . Linear regression analysis showed that there is significant reductio n in the OPG levels (P < 0.05) in calves infected with. Eimeria, aged between 7 and 38 weeks. Finally, the data are discussed in relation to management practices and the acquisition of immunity.