DES MOINES, Iowa (AP) -- An animal rights group is taking responsibility for hanging a sign on the Iowa State Fair butter cow, saying it represents "humankind's tyranny over defenseless animals."

The Des Moines Register is reporting (http://bit.ly/ptoknB ) the small sign reading "Go vegan" was attached to the butter cow with tape Sunday morning. Fair spokeswoman Lori Chappel says the butter cow wasn't damaged.

The newspaper received an e-mail from an animal rights group saying one or more activists from another group got past a guard in the Agriculture Building, climbed a wall and got into the refrigerated case where the butter sculptures are located. The e-mail said the group wanted to bring attention to animals used for food.

The group says the sign was up for about two hours.

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Information from: The Des Moines Register, http://www.desmoinesregister.com

Copyright 2011 The AP.