Until recently to select for facial eczema (FE) tolerance breeders have had to dose animals with sporodesmin and blood test for an enzyme called gamma glutamyl transferase (GGT) which indicates the level of liver breakdown due to the fungal toxin. With the development of Sheep 50K – A DNA test that determines the genetic potential of an animal for various traits since 2013 we have been selecting animals for FE tolerance based on the DNA of the animal.
For the last three years we have also used sires from leading North Island Breeders that have been testing and breeding for FE tolerance for a number of years. One sire Waihora 4422/10 is the no. 1 ranked sire on the SIL-ACE trait leader list for FE tolerance. We have tested progeny of these rams for the last two years. In spring 2015 we tested progeny from this leading sire at a dose rate of 0.5mg sporodesmin/kg bodyweight and have selected one of these to use that had no liver damage at all. He is being used this autumn also in a leading stud in the Waikato.
The swing to begin selection for FE tolerance is due to the growing number of North Island and Nelson clients that we have that are faced with natural FE challenges in their sheep. Also looking long term it will only take a 2 degree increase in temperatures in the South Island due to global warming for FE to become an issue down here. Like any breeding program it takes time. We want to have FE tolerant sheep before we need it!
We have been breeding for worm resistance for over twenty years so breeding for FE tolerance will add to the disease resistance/tolerance of Nithdale Romneys.