Originally Posted by DrumRunner
If you question it at all, always test, not only have the owner's test. You should have her tested as well BEFORE making any commitment to her. HERDA can stay hidden in young horses with no symptoms. It will usually surface when they are started to saddle and will just progress from there. Once diagnosed with HERDA you'll probably have to have her PTS and if she is a carrier she's not suitable for breeding.
Well, while you are partially correct.. not fully.
With appropriate testing to other tested individuals, a carrier can be a breeding animal and contribute a lot to the gene pool.
You just have to be responsible and test your breeding stock before hand. A carrier will not have any symptoms of the disease, nor be affected in any way by it, so there is no reason to not use them or to put them to sleep.
Now if you are an irresponsible breeder that isn't testing your breeding stock, then no you probably shouldn't breed a mare with HERDA (or anything more than dust bunnies).