I have wondered that myself.
Especially of the horse that weighs 1,100 pounds and I can hardly lift the BIG aluminum shovel full of poop he leaves in one pile. Sometimes I can't fit one pile onto that big aluminum shovel.
He leaves a minimum of five of those piles in his stall every night --- he should not weigh 1,100 pounds. I have a horse that is two inches taller and also weighs 1,100 pounds. I can get 1-1/3 piles of his poop on that aluminum shovel; maybe even 1-1/2 piles.
Not only is something wrong with that picture, something is wronnng with this conversation --- thanks for bringing this up