The very fact that humans grants "rights" to animal just proves that animals don't have rights. They just have what humans give them.
Well, in truth the exact same can be said of humans. Humans (typically those who sit in the legislative, judicial, and executive branches of government) grant rights to other humans. People have rights by virtue of their
citizenship to a country, not their humanity. A person from North Korea doesn't have the same rights as a person from Canada. It's one of the reasons the human rights abuses at Guantamino Bay were as prevalent as they were - that piece is land is funny in that, while it is located in Cuba, a treaty signed in the early 1900s gave the US complete control and jurisdiction over the land in which the detention centre is located on through a rental lease. So you have a land without laws and thus a land without rights. And I'm not disagreeing with you - I just find the topic exceptionally fascinating. I'm only saying that rights are granted to both humans and animals, alike.
But this question asks whether or not animals
should have rights - not whether they do. There is actual an important distinction to be made between animal
rights and animal
welfare. Animal rights activists attempt to elevate the species of animals to equality with humans - a core tenet of animal rights philosophy is that no species on this planet is better than another; therefore, humans have no right to dominate over, use, breed, or eat nonhuman species.
This, I can't say is true. I don't believe in any god or religion, but it is clear that it's up to mankind to be stewards of the Earth. Animals have very obvious restrictions that make them incapable of being so - although, on second thought I imagine animals could do a better job than we are.
I tend to lean towards animal welfare than rights. Animals are sentient life forms - they feel pain, many can recognize their own reflection, and they have a consciousness that enables them to make decisions and reason. Sure, it's not to the extent that humans can reason - but not all humans are able to reason to the same degree either. However, because all animals suffer when they are tortured and slaughtered, I do believe they deserve as much consideration as a human who suffers and all measures to ease an animal's pain and suffering should be considered. I think there are some unacceptable uses of animals including fur, cosmetic testing, dog-fighting, and to be honest, I would even go as far as to say factory farming.
I don't object to the consumption of animals, or the humane use of them for medical research. However, I would like to see cruel practises eliminated - thus I'm entirely in favour of stricter animal welfare laws and harsher punishments for those that violate them.