This is from Nurse Mare Foals:
Orphan nurse mare foals are a product of the nurse mare farm industry. Most people associate these babies with PMU (Pregnant Mare Urine) babies and that couldn't be farther from the truth. PMU babies are generated as a result of breeding mares specifically for their urine, as menopause drugs for women are manufactured from hormones found within their urine when they are pregnant. Though they are both generating foals, usually PMU ranches allow the mares to nurse their young.
Nurse mare farms breed mares to random studs for the purpose of bringing the mares into lactation. The pregnancies they carry are unwanted, the milk is the name of the game.
Once foaled, these mares are then leased out to other farms to nurse foals other than their own (usually high dollar show or race horses). Their own foals are pulled away from them anywhere between 1 day and 1 week of age. Their foals are then discarded due to the level care they require and the costs associated to raise the orphan foals.
There are many reasons why people think nurse mares are necessary. A mare may die in birth, a mare can immediately return to work as a show or racehorse, she may be transported immediately without having to worry about transporting her foal, or she can be covered (bred) on the foal heat, etc.
This has been happening for 30+ years, but has remained "underground" so unfortunately, it could be happening right down the street and you probably wouldn't know it.
Many myths have surrounded this industry, including the most popular; it's a Thoroughbred thing; and its understandable why people have come to that conclusion. In order for a Thoroughbred to be eligible for registry, they must have been a live cover breeding. Though the racing industry is a major player, many different breeds are involved in the practice. So to answer the question: "What is a nurse mare foal?" These foals are unfortunate by-products of a industry in practice of leasing a mare out for her milk.
The biggest challenge these orphans face is the myth that they are worthless. These foals will grow and mature the same way any other horse would. They just need a chance! Typically these make much calmer, relaxed, and bombproof horses. The bond they share with people is usually unsurpassed. They have been there and seen it all by the time a regular foal is being weaned.
If you find you are caring for an orphan foal, whether it is a PMU, nurse mare baby, rejected by its dam, or otherwise, it is very important to remember that each individual foal is different. So just because it works for one foal does not mean it applies to all! Always use common sense when making choices & decisions on your foal's care. Don't be afraid to ask someone with more experience, and always gather all the info you can through all the available sources. Remember that a little hard work & effort really pays off as you see these guys grow into the healthy & beautiful horses they will become.
And here are some videos about nurse mare foals: