EIMERIA-ALABAMENSIS INFECTION AS A CAUSE OF DIARRHEA IN CALVES AT PASTURE

Large numbers of oocysts of Eimeria alabamensis have been found in the faeces of calves suffering from diarrhoea shortly after being turned out to pasture. To investigate the source and clinical significance of this coccidial infection, the numbers of oocysts excreted, the consis tency of the faeces and the growth rates of four groups of 12 calves w ere compared. Group I calves were kept indoors and their diet was unch anged, Group II calves were turned out onto a previously ungrazed past ure, Group III calves were turned out onto a permanent pasture and Gro up IV calves were kept indoors and fed cut grass from a previously ung razed field. Eight days after the animals were turned out there was an almost 1000-fold increase in the numbers of oocysts in the faeces of Group III calves, the dominant species being E. alabamensis, but there were only minor fluctuations in the numbers of oocysts excreted by th e other groups. It was therefore concluded that the source of the infe ction was oocysts that had overwintered on the permanent pasture. Most of the calves in Group III developed watery diarrhoea 5 days after tu rnout, but there was only a slight softening of the faeces of the calv es in Groups II and IV at about the same time. The faeces of the calve s in Group I was of firm consistency throughout the trial. The calves in Group III lost 18 kg during the 24 day period following turnout, wh ereas the calves in the other groups gained between 6 and 18 kg.