Two not too very bright city guys decided to go into the dairy 
business. They drove up to a dairy farm and asked the owner if 
he had any cows for sale. 
The owner had been trying to get rid of a non performing bull for 
years told them he would let his best producing cow go for a 
mere one thousand dollars. 

The 2 guys said wonderful and loaded up the bull and left.
They got back to their place and tried to milk the bull but didn't 
get any milk. So one of the guys ran back to the farmer to find out 
how to get the milk flowing. The farmer told them they had to 
make the cow drink plenty of water and then pump the tail up and 
down. Satisfied the city slicker went back and he and his partner 
pushed the bull down to the stream. 

Well, the bull wasn't very thirsty and didn't drink so one guy held 
the bulls head in the water and the other guy pumped igorously 
with the tail. About that time the bull decided to take advantage of 
the raised tail and to dump some solids. The guy pumping yelled 
to his friend "Raise his head he is sucking mud."