31 March 2000

Worm resistance index

SHEEP producers could save time and money if an estimated breeding value for resistance to worm infection could be developed.

Work at the Welsh Institute of Rural Studies at Aberystwyth found that parasite resistance in young lambs is limited, but that selection for resistance would be more successful in older sheep.

The research, by PhD student Kirsty Howells, looked at parasite resistance in groups of Hardy Speckled Face x Bluefaced Leicester and Scottish Blackface x Bluefaced Leicester lambs over a two-year period. Faecal samples were collected four weeks after drenching with a benzimidazole product at set times each year.

Results were based on the outcome of faecal egg counts, where the number of worm eggs in faeces was counted as a measure of the animals resistance or susceptibility to parasites.

Mrs Howells found that Hardy Speckled Face x lambs had a lower faecal egg count than Scottish Blackface x lambs.

She believes that by choosing animals with resistance to internal parasites, producers might be able to worm sheep less often. &#42