I 100% agree with @manes with the support of the JC with no recipient mares, cloning, and AI. AI only works in small breed registries. Yes, AI helped a lot with refining Standardbreds, but if you look at pedigrees now, we are bottlenecking with a handful of sires. Sometimes it is that stallion who may not have been a "big name" but has some great genes that will nick well and improve the breed and this is what allows smaller breeding operations or my personal favorite, the homebred, to properly flourish. Now, it is rare for a good racing mare to produce in the breeding shed, not sure if it is the hormones or what but if a top race mare does drop foals, maybe 1 turns out great, the rest just have a bad a$$ momma in their pedigree. Is Zenyatta a bad broodmare? Not yet, her first is turning into a very nice event horse, her second baby of racing age has yet to break his maiden, and the filly is just a yearling. You cannot blame the mare for a paddock accident and it has been a tough year for slipping, several mares (both of note and obscure) have slipped their foals, so not sure if there is an issue in common or just a bad year. She may be bred back although it is late in the year, or giver her the summer off and try again next season.