Only corporations and humans are people.
Animals should not be granted personhood because they are not people. Animals should be slow smoked at approximatley 225 deg. F.
Wiki says supporters of corporations having the protection of the U.S. Constitution claim its because corporations "are organizations of people, and that these people should not be deprived of their human rights when they act collectively." Personhood rights allow them to "sue and to be sued", provide "a single entity for easier taxation and regulation", simplify "complex transactions that would otherwise involve, in the case of large corporations, thousands of people" and these things protect the rights of the shareholders" collectively.
So, if an animal 1.) is made up of people; 2.) has the ability to sue and be sued; and 3.) pays taxes - then they should probably be granted personhood style protection. Otherwise, they should be treated as a sole-proprietorship - meaning, the rights and obligations pass through to the owner of the business or animal. The owner still has obligations (in a business they might have fair hire laws, etc.), so for an animal, the owner would have "fair treatment" obligations.
The US is an odd ship. The captain yells out when he sees obtacles , but 535 individual propellers do the steering.
While they are not persons; Elephants, Great Apes and Dolphins should have greater legal protections.
Economic Left/Right: -7.25, Authoritarian/Libertarian:-7.13
All over the place, from the popular culture to the propaganda system, there is constant pressure to make people feel that they are helpless, that the only role they can have is to ratify decisions and to consume. -Noam Chomsky
I support bacteria rights. They should have the right to work, vote, have sex, etc.