A farmer buys a cute little filly that he plans on racing next season, but when gets her home, his old stallion smells her and wants her and starts kicking up dust. The farmer doesn't want her knocked up, because she won't be able to race, so he calls the vet.
The vet tells him to tie a bed sheet around the filly's rump to keep the stallion away. So that day, the farmer does just that. The next day, the farmer goes out to the corral to make sure the vet's solution worked, but the filly's nowhere to be found.
The farmer follows her hoof trail to the neighbour's farm and sees the neighbour' kid out by their barn. "Hey boy, did you see a filly run by with a bed sheet tied around her rump?" the farmer asks.
The kid replies, "No sir, but one dashed past here early this morning with a handkerchief sticking out of her ass!!"