Sad to say, but no part of the horse goes to waste. Horse parts (along with other dead animals) are used in many things that will utterly surprise you.
Foal skins are called "pony skin". It is used to make purses, shoes, etc.
Mane and tail are sent to china to make paint brushes.
Small intestines are sent to Egypt to make sausage casings.
After the horse is slaughtered and all the meat that is fit for human consumption is taken, the carcass is then sent to a rendering plant. It is then used in a variety of products such as:
soap
polish
cement
ink
crayola crayons
pet food
This is just to name a few. Check out the undated horse slaughter page for more information and more products. Some of them you have to see to believe!