Faecal samples from a group of lambs at pasture were screened at weekl
y intervals for nine weeks for the presence of Giardia species using a
modified zinc sulphate flotation method. Fifty-nine of 86 lambs (68-6
per cent) excreted giardia cysts on one or more occasions. They were
first detected at approximately three weeks of age and the highest inc
idence of excretion of cysts occurred when the lambs reached a mean ag
e of 37 days. The lambs had diarrhoea but it was attributed to the pre
sence of Eimeria ovinoidalis.