A zebra goes on an exchange visit to an English farm and on her arrival, she goes around finding out about each of the different animals.
She meets a pig - "who are you and what do you do?"
"I'm a pig - the farmer fattens me up all my life and when I die, I'm sent off to be slaughtered and my meat feeds people and my skin is used to make useful things".
Next, a chicken - "I'm a chicken - a lay eggs every morning and when I die, my meat is used for food and my feathers are used to make bedding".
As sheep; "I'm a sheep, I'm a sheep and I eat grass and the farmer regularly cuts my wool to make clothes, and when I die my meat feeds people and my skin is taken o make coats".   
A cow - "I'm a cow and I'm milked every morning, and when I die, my skin is used to make leather and my meat feeds people".
Finally, the zebra trots off to the meadow to eat some grass, and in the corner of the field she sees an enormous great bull.
She trots over and says, "I suppose you're another cow?"
The bull turns around and glowers, "Feck off", he says, "I'm a bull"
"What do you do?"
"Get those feckin' pyjamas off and I'll show you".
Jim Carroll