Field studies of the immunisation of lambs with drug-abbreviated infections of Trichostrongylus colubriformis and Ostertagia circumcincta.
Fifty, 5-6 month-old lambs were randomly allocated to five equal groups. Three groups of lambs were immunised by three oxfendazole-abbreviated (artificial) infections of Trichostrongylus colubriformis and Ostertagia circumcincta. Group 1 was immunised with a high dose of larvae, Group 2 with a medium dose and Group 3 with a low dose. A fourth group was treated with oxfendazole only and a fifth group was not treated (control). All groups were grazed together on pasture naturally contaminated with nematode larvae. Immunisation significantly reduced the number of eggs per gram of faeces in all three groups, but the lowest faecal egg count was seen in Group 3 (immunised with the lowest number of larvae). Significantly better liveweight gains and wool weight were observed in Group 2 animals than in the control group. Of all anthelmintic-treated animals, only Group 1 lambs did not have a significantly lower dag weight than controls.
Stankiewicz
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AgResearch, Wallaceville Animal Research Centre, PO Box 40-063, Upper Hutt, New Zealand.
Hadas
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