and there was also the chance that he'd at least be a donor for artificial insemination.
Actually, there wasn't. Thoroughbreds aren't allowed to be created via artificial insemination. It has to be done the old fashion way.
That's why so much time and money was spent trying to heal Barbaro. Unless he was able to stand on his own hind two legs, his offspring wouldn't have been thoroughbreds, wouldn't have been able to compete, and wouldn't have been worth 1/100 a real thoroughbred is.
It was all or nothing. And for a while it looked like he might have pulled through.