Resistance----The ability of the sheep to resist the challenge of the worms – To inhibit their development and reduce the number of eggs laid
Resilience ---The ability of the sheep to continue to be productive whilst hosting a large worm burden which continues to lay eggs
Resilience is great but it means that the eggs are still being shed onto the pasture to breed/multiply and infest other sheep
Resistant ewes on the other hand kill worm eggs and reduce the worm burden for susceptible animals like young lambs
Showing no outward symptoms is great but a moderate worm burden still means slower growth rates etc
There is a school of thought that says have resistant mothers and a resilient terminal sire
Problem is that resistance/resilience only starts being shown by lambs when they get to 6 months old ----key i think (at the moment
) is to have lambs slowly introduced to worms which helps them start to show their genetic resistance
We try to breed for resistance and also for animals that show resistance earlier in their lives