Roundworm resistance initiative to help sheep breeders

Lleyn sheep producers will be able to select animals for their resistance to roundworm, based on an estimated breeding value (EBV). 

This is the result of a University of Glasgow project, which found the antibody response against the larval stage of a roundworm can be used as a biological indicator for the host’s response to the infection.

Immunoglobulin A (IgA) is an antibody that is critical to immune function in mucous membranes. By measuring it in saliva, a new phenotype that differs between sheep can be identified. High numbers of IgA have been shown to regulate worm growth and fecundity, which results in decreased egg output.  

A grant from the Agriculture & Horticulture Development Board (AHDB) Beef & Lamb supported the collection of saliva IgA and faecal egg count (FEC) samples for the study. A further grant helped geneticists at Scotland’s Rural College (SRUC) to analyse raw data and investigate genetic influences on saliva IgA, and subsequently convert these measurements into EBVs which will let breeders make more informed decisions.

“Since 2013, 7,899 Lleyn saliva samples have been collected and uploaded to the Signet database,” said Sam Boon, Signet breeding manager. “When combined with the ongoing collection of FEC data, this has created a large commercial dataset on which to estimate heritability values for this new trait and study the genetic relationships between this and the FEC EBVs.”

New Saliva Iga EBVs are expressed in units of IgA activity. A high EBV means that an animal is genetically better at dealing with worms. This juxtaposes FEC EBVs, where breeders are reminded that low, negative values are indicators of breeding potential to put fewer eggs out onto pasture.

“The Lleyn breeders involved are very enthusiastic about the potential for this new technology and its application to the selection of genetically superior sheep,” added Boon.

“In the future, planned matings will take place between high-EBV animals for these traits to see the impact it has on progeny performance.”

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