Effect of four grass species on lamb parasitism and growth

Abstract

Parasite epidemiology and lamb growth were investigated in a study involving four single-species swards (browntop, Yorkshire fog, perennial ryegrass and tall fescue). Lambs were set-stocked from December (weaning) to early June on 1 ha paddocks grazed to a constant height of approximately 5 cm by varying stock numbers (average 35 lambs/ha). Lambs were weighed and faecal sampled fortnightly and were either "suppression -drenched" fortnightly with ivermectin or "trigger- drenched" when any group mean egg count reached 1500 epg, at which time all groups were drenched. "Trigger-drenched" groups were treated on 4 occasions. At the end of the trial, suppressively drenched lambs on ryegrass were significantly heavier than those on the other grasses (P