The availability of ovine infective trichostrongyle larvae on forested paddocks

A study was made to compare the numbers of infective ovine nematode parasite larvae on an open pastured block and an adjacent block forested with Pinus radiata at 200 stems per hectare. Each block consisted of two paddocks which had similar nematode parasite egg contamination. Infective larvae of six genera were recovered over a 12 month period viz., Trichostrongylus spp., Ostertagia spp., Cooperia spp., Nematodirus spp., Chabertia/Oesophagostomum spp. and Haemonchus sp. A significantly higher recovery of Trichostrongylus spp. (p<0.01) and Ostertagia spp. (p<0.05) from the pine forested block was probably due to the more favourable climatic environment under the pines. The lower mean body weights of sheep grazing the pine block was considered to be due to the greater exposure to infective larvae and marginal under-nutrition.