Patterns of Eimeria excretion in young Icelandic calves

Faecal samples were collected from a total of 11 calves on three dairy farms (four from two farms and three from one) where calves generally thrive well and no anti-coccidial treatment is habitually carried out. One of the farms keeps calves in groups on hay/straw bedding, one keeps calves in pairs on plastic slats and then in groups on concrete slats, and the third one keeps calves in groups on concrete slats. Faecal consistency and the total number of Eimeria spp. oocysts per gram faeces (OPG) were determined and species identification was carried out by morphology. Eimeria oocysts were detected in all calves at some point of the study period, and diarrhoea was seen in 55% of the calves. The highest peak in oocyst excretion was 69,300 OPG. The first peak in oocyst excretion was seen 2-3 weeks after calves had been moved to group pens, and a second peak was seen 2-3 weeks later. Nine Eimeria species were found, including E. bovis and E. zuernii. The results are in accordance with previous studies showing that one of the risk factors for Eimeria infection in calves is entering a group pen where older calves are already being kept.