Productivity and pasture intake of defaunated crossbred sheep flocks

Abstract

From a flock of pregnant crossbred ewes, 63 were established as protozoa-free by treatment with alkanate 3SL3 and 64 ewes were maintained as controls. The controls included 20 ewes, which had been defaunated and subsequently re-inoculated with protozoa. After lambing, both flocks were grazed in a 6-paddock rotation until weaning at 20 weeks of age. Defaunated ewes were heavier than control ewes throughout lactation and had a higher urinary allantoin concentration than the control ewes. Intake and apparent digestibility of pasture dry matter by ewes did not differ between groups although these estimates were confounded by differences in pasture composition between the paddocks used. Both groups selected a diet with digestibility approximately 10% units higher than the bulk digestibility of pasture on offer. Control ewes selected a higher proportion of white clover in their diet than was available in the pasture (24% v. 2%) but defaunated ewes did not exhibit preferential selection for clover. Lambs from defaunated ewes were heavier at birth, remained heavier until weaning and grew more wool than lambs from control ewes. Contamination of fauna-free ewes and lambs with protozoa was first observed at weaning and protozoa were detected in 41 out of 60 lambs, 4 weeks after contamination was first detected. Study of defaunated ewes returned to a flock of untreated ewes confirmed rapid spread of contamination into defaunated ewes with small entodiniomorph protozoa establishing first.