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In a note on the tb_breeding_theory webgroup yesterday, Jay Leimbach wrote about epigenetics and some thoughts about how “methyl tags” might turn on or off some of the genes in a horse’s makeup.

Leimbach wrote:

… the growing science of epigentics adds a new wrinkle to the old model of mutation:
NOT that the gene structure itself mutates, but that methyl tags attach themselves to the genes under adverse conditions, and literally smother the gene’s operation, so that important functions can be turned “off” completely. And these methyl tags can be passed on to subsequent generations ….

Well, ick! As if breeding horses isn’t sufficiently difficult already.

Well, if you’re suspecting this is the sort of thing that could get my back up, get me crow-stepping a bit, you’re right.

Then, Herr Leimbach enlarged his discussion to suggest that Slew o’ Gold, Capote (really?), and Spend a Buck might be examples of epigenetic failure. This engendered quite a bit of mental bucking, with the result that I wrote this to get the burr from under my saddle pad.

Jay is actually a very nice, decent, curious fellow, but this epigenetics biz is really too much.

Consider, for instance, that Horse of the Year Spend a Buck was not very successful in the States, went to Brazil, where he sired G1 winners Hard Buck, Pico Central, and Einstein on Southern Hemisphere time. For the Northern Hemisphere seasons, Spend a Buck returned to the US, where the Kentucky Derby winner still wasn’t notably successful.

For epigenetics to be involved in the difference between Spend a Buck’s success in Brazil and lack thereof here, the stuff would have to switch on or off every time the horse crossed the Equator. Now just how am I going to buy that?

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