All you have to do is look at these foals to know the bulk of them are not nurse mare foals. That's flamingly obvious. Nurse mares are often Thoroughbreds themselves. Some outfits use Draft mares because they are able to produce enough milk for their own and another foal. So generally the offspring will be all thoroughbred or half Thoroughbred. The nursemare providers I talked to? I don't know what your question down there is even asking. I called up people who lease nurse mares as an organized business. There are also similar outfits that keep mares for embryo transfer. Again, more mares are needed than transfers actually done.