Distinguishing between parasite resistance and resilience is very import for a sheep operation that wants to produce quality breeding stock.
Probably one of the most eye opening events from 2016 was when I realized and understood the difference between parasite resistance and resilience, We are breeding registered Katahdins that are 100% grass fed, so having parasite resistant sheep is key to our farm.
Resilience
A resilient sheep can tolerate a large parasite load without showing any physical signs. A resilient sheep is one that has a large number of parasites based on fecal egg count testing and does not have to be dewormed based on FAMACHA and other clinical signs.
Parasite Resistance
A parasite resistant sheep is one that does not have a lot of parasites despite being exposed to a large number of parasite eggs. Just having a low fecal egg count is not enough, the fecal egg count has to be done at a time when the animal is exposed to a large number of parasites. A fecal egg count done on a sheep that is exposed to no parasites tells you very little.
Resilience vs Parasite Resistance
A resilient sheep might not need deworming but could still be carrying a large number of parasites and shedding them to further contaminate your pastures and infect other sheep
A resistant sheep does not carry a large number of parasites and therefore does not shed parasites or contaminate your pasture
Parasites need to eat, carrying a large number of parasites impacts the performance of the animal, it is better not to carry parasites
When purchasing breeding stock for parasite resistance you must get data and proof that shows the animal is really parasite resistant
Not having to deworm does not indicate resilience or resistance
At Gibraltar Farm we do FAMACHA and collect fecal samples and perform fecal egg count tests multiple times per year. We use this information to help with breeding, treatment and management decisions. In 2017 we plan to sell our first breeding stock, we will make sure that when we say a sheep is parasite resistant that we have data to back it up.