Sunday, December 2, 2012

Facial Eczema Dose Test Results

9179, passed best of the bunch
 21 day GGT test results are in for the 5 stud sires I had dose tested under the Ramguard program.
Facial eczema, (commonly referred FE), is an insidious disease of all pasture based animals here, caused by a toxin produced by a saprophitic fungus, pithomyces chartarum, that thrives after summer dry has browned off pasture.
Fortunately, sheep have a genetic resistance to the effects of sporidesmin toxin, with quite a high heritability component. The Ramguard program involves administering a very carefully calculated dose of sporidesmin and measuring the response indicated by blood test before, and 21 days after.
By this means, the resistance factor can be identified in pivotal individual animals, and spread through a flock relatively quickly, capturing and ensuring a safe and non-chemical avoidance of what can be a highly debilitative challenge to both flock, and bank account.
9069 and 9269, good passes also
Having your flock resident long term in a district where FE is more prevalent is a distinct advantage, as the sub-clinical effects of the disease whittle away at fertility, and indirectly assist building a resistant population of those sheep unscathed.
In my recorded nucleus ram breeding flock, I also GGT blood screen from free-range pasture, all in-coming replacement females, eliminating those showing early intolerance, and therefore contributing to the robustness of the FE/DPX selection index.
Waione 75-08 posting a "slight" reaction, was a bit of a disappointment, as I have big raps on this ram for his growth factor. He was actually 35kg heavier bodyweight than the mean of the other 4 rams tested, on which the dose rate is based, so he got a proportionately far bigger "drink".
One could argue, being a growth spec sire, that he neednt eat as much grass au naturale per kg liveweight, and therefore ingest as much toxin, to maintain and grow, as the others.
It is a known that animals laying down protein, dont succumb to toxin challenge as readily, as conversely do those losing it.
I would expect gene-lines that have a high muscling factor would be less susceptible, and this is born out in my experience with rams I've used, from Norman Early's Ashburton flock, and the highly muscled 544/07 from Lincoln University, both Canterbury flocks where FE is virtually unknown.