A project supported by AHDB has produced an estimated breeding value (EBV) which will enable Lleyn sheep breeders to select animals for their resistance to roundworm.
The project, conducted by a team of researchers at the University of Glasgow, found the antibody response against the larval stage of a roundworm infection can be used as a biological marker for host response to infection.
Immunoglobulin A (IgA) is an antibody critical to immune function in mucous membranes. Measuring this in saliva provides a new phenotype through which differences between sheep can be identified.
High levels of IgA have been shown to regulate both worm growth and fecundity, which leads to decreased egg output.
AHDB Beef & Lamb supported the collection of saliva IgA and faecal egg count (FEC) samples for the study by awarding the Performance Recorded Lleyn Breeders Group a Farm Innovation Grant (FIG) in 2013.
In 2015, a further AHDB FIG was granted to enable geneticists at Scotland’s Rural College (SRUC) to analyse the raw data and investigate genetic influences on saliva IgA and convert these new measurements into EBVs which will enable breeders to make more informed decisions.
'Large commercial dataset'
Sam Boon, Signet breeding manager, said: “Since 2013, 7,899 Lleyn saliva samples have been collected and uploaded to the Signet database.
“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.”
The new Saliva IgA EBVs are expressed in units of IgA activity; high EBVs mean that an animal is genetically better at dealing with worms.
This is in contrast to the expression of FEC EBVs, where breeders are reminded that low, negative values are indicators of the breeding potential to put fewer eggs out onto pasture.
Mr Boon continued: “The Lleyn breeders involved are very enthusiastic about the potential for this new technology and its application to the selection of genetically superior sheep.
“In the future, planned matings will take place between high EBV animals for these traits to see the impact it has on progeny performance.”
