Father and young son go to a horse auction.
The young son watches as his father moves from horse to horse, running his hands up and down the horse’s legs, rump and chest.
After a few minutes the son asks
“Dad, why are you doing that?”
His father replied “Because when I’m buying horses I have to make sure that they are healthy and in good shape before I buy.”
The son, slightly worried said “Dad, I think the postman wants to buy mum.”