Flockmasters need to breed for greater worm resistance

WIDESPREAD ANTHELMENTIC resistance across the country means English lamb producers must place greater priority on breeding for genetic resistance to worms, advises EBLEX.

Latest testing reveals that resistance to benzimidazole white drenches now affects 80% of lowland flocks, with some farms seeing resistance to all three main classes of wormer, says MLC’s Signet Breeding Services manager Sam Boon.

“Financial estimates show that using rams with high inherent levels of resistance to intestinal worms can save £2 a ewe a year in vet costs.

“With increased growth rates from resistant lambs as well as decreased levels of worm eggs shed on pasture, the value of breeding worm resistance becomes even more apparent.”

Growing numbers of Texel, Suffolk and Charollais breeders are now using faecal egg count (FEC) technology to produce and market rams with Estimated Breeding Values for worm resistance alongside other key terminal sire EBVs, adds Mr Boon.

As with EBVs, ram FEC EBVs are relative to an average. “Based on the number of worm eggs recorded/gram of faeces, these typically range from -1 to +1. Negative values indicate worm levels lower than the average, which is 0,” he says.

Assuming rams with higher levels of worm resistance are used on groups of ewes of similar breeding potential under similar conditions, Mr Boon says their progeny will have a lower requirement for anthelmentic treatment.