Abstract The effect of internal parasites on the performance of lambs grazing different forage species was examined in two experiments. In Experiment 1, 300 Coopworth lambs grazed stands of Nui ryegrass, Wana cocksfoot, Au Triumph tall fescue, Puna chicory, or Otaio lucerne for 64 days between February and April 1992. Lambs were either infected with 10000 mixed species L3 larvae at the start of the grazing or maintained free of parasites by fortnightly drenching with ivermectin. Herbage was offered at either 2 or 4 kg DM/head per day (green). In Experiment 2, Nui ryegrass was replaced with low‐endophyte Ruanui ryegrass and lambs were infected with 19500 L3 larvae 21 days before grazing which commenced on 2 February 1993 and continued for 100 days. In Experiment 1, few herbage larvae were recovered during grazing and differences among forage species were not significant. In Experiment 2, more larvae per kg DM were recovered from the grass swards than from either chicory or lucerne (P < 0.05), differences a...
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