Animal rights, also known as animal liberation, is the idea that the most basic interests of non-human animals should be afforded the same consideration as the similar interests of human beings.

The idea of at least some awarding rights to animals has the support of legal scholars of Harvard Law School. Animal rights is routinely covered in universities in philosophy or applied ethics courses, and as of spring 2010 animal law was taught in 125 law schools in the United States and Canada.
Critics of the idea argue that animals are unable to enter into a social contract or make moral choices, and for that reason cannot be regarded as possessors of rights. And therefore only humans have rights.

There has also been criticism,in particular the destruction of fur farms and animal laboratories by the Animal Liberation Front. A parallel argument is that there is nothing inherently wrong with using animals as resources so long there is no unnecessary suffering, a view known as the animal welfare position.
The 21st-century debates about how humans should treat animals can be traced to the ancient world.

The idea that the use of animals by humans—for food, clothing, entertainment, and as research subjects—is morally acceptable, springs mainly from two sources
Richard Ryder writes that the first known legislation against animal cruelty in the English-speaking world was passed in Ireland in 1635. It prohibited pulling wool off sheep, and the attaching of ploughs to horses' tails, referring to "the cruelty used to beasts," which Ryder writes is probably the earliest reference to this concept in the English language.

Animal suffering
Singer writes that commentators on all sides of the debate now accept that animals suffer and feel pain, although it was not always so.

According to Singer, scientific publications have made it clear over the last two decades that the majority of researchers do believe animals suffer and feel pain, though it continues to be argued that their suffering may be reduced by an inability to experience the same dread of anticipation as humans, or to remember the suffering as vividly

The problem of animal suffering, and animal consciousness in general, arises primarily because animals have no language, leading scientists to argue that it is impossible to know when an animal is suffering.

http://www.educar.org/comun/derechoshumanos/animales
http://www.animal-rights.com/
http://en.wikipedia.org/wiki/Animal_rights