The length of a horse's digestive tract is about 100 feet long and has a capacity of 40-50 gallons. The small intestine is about 70 feet longs and will hold about 12 gallons.
A resting horse breathes 8-16 times/minute and inhales about 250 cubic inches of air with each breath.
Blood makes up about 7% of a horse's weight. A resting horse has a heart rate of 38-40 times/minute.
The front legs of a horse have no skeletal attachment to to axial skeleton (trunk) of a horse, just muscular connections. They bear 60-65% of the horses weight.
A horse's hoof grows about 3/8 inch per month, with the front feet often growing slower than the hind feet. Shod fee grow slower than unshod feet. and stallion feet often grow slower than mare or gelding feet.
The frog of the hoof helps with blood circulation and shock absorption.
A sharp object (nail, stick, or stone) an pierce a horse's hoof and take as long as a year before emerging out the other end--no wonder some horses seem to never recover from lameness!
Reasons why a horse with a broken leg has a limited chance of survival:
1.The lower leg has little blood circulation or muscle, which can easily disrupt blood flow and lead to infection.
2. Recovery is difficult-not all horses will tolerate being in a sling, and some thrash so much coming out of anesthesia that they re-injure themselves. (The race horse Barbaro was suspended in a swimming pool while waking after surgery to minimize damage. Even with a successful surgery, Barbaro was only given a 50% chance of survival due to all four of these reasons).
3. Laminitis can result in the "good" legs due to overloading as the horse favors the bad one. (This was why Barbaro was ultimately euthanized.)
4. The anesthetic can cause life-threatening constipation in a horse.
Taken from the Horse Production class text: Equine Science 4th edition by Rick Parker.