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Activity I.1: Over-Wintering of Gastrointestinal Parasites in Organic Sheep Production

Activity Summary

This project will improve understanding of factors that affect two major sources of gastrointestinal nematodes (GIN) responsible for parasitic infections in sheep: over-wintering of hypobiotic larvae in adult ewes and the subsequent periparturient egg rise (PPER) which then contaminates spring pasture resulting in infection of naïve lambs; and over-wintering of infective L3 larvae on pasture from contamination from the previous grazing season.   The first – over-wintering in ewes - will be done by examining PPER levels in ewes under different management systems, specifically out-of-season lambing, how individual animal factors influence PPER levels, and the impact of strategic and limited use of anthelmintics in reducing this rise.  The effect of winter climate on survival of infective GIN larvae, including Haemonchus contortus, on pastures will be done by examination of presence of larvae on contaminated pasture plots.  One acre plots of pasture grazed that season by infected sheep will be assessed from the fall after animal removal until the spring before turn-out.  Micro-climate data will be collected using time-temperature-humidity recorders at ground and human height.  Presence and type of GIN larvae will be assessed by larval pasture sampling when not covered by snow.  Infectivity of present larvae will be assessed by spring grazing of naïve tracer lambs. This information will be used to develop a strategic integrated parasite control program for both organic and conventional sheep flocks in central Canada which will reduce level of disease, reliance on anthelmintics, and thus improve the productivity of this sector. 



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