It is an interesting thing to compare some of the body composition values between horse and human, as that often gives us insight into the incredible athlete that is the horse.

For example, the human heart is 0.47 % of the live weight or about 0.3 kg (or less than a pound and the size of your fist), whereas the heart of a horse is huge!  It is about 0.66 % of live weight of the horse or about 4.5 kg (or about 10 pounds).  The largest horse heart is believed to be the one in the great Secretariat, at 21 pounds!

For more on the amazing equine heart:

A Quick Look at the Amazing Equine Heart

The spleen of a human is about 0.26% of live weight but for the horse, the spleen is 1.11% of body weight, which is huge!  Any idea why the spleen of the horse is special compared to the human?

Muscle is about the same for both (about 40% of live weight) but when we look at the gut of the horse and human, the human gut accounts for 1.4% of live weight, whereas the horse has a gi.i. tract that weighs in at 12.7% of live weight!  That’s a lot of weight for the horse to be carrying around when running!