I tend to weigh on the side that sentient animals should receive protections similar to the protections we give to children or to adults deemed legally incompetent. That means they can't exercise many of the rights that we recognize adult humans have, but neither can they be wantonly exploited, physically or psychologically harmed.
There are already animal cruelty laws that could be amended to grant better protection from human-on-animal neglect and abuse. The problem with giving them rights is that they'd apply to animal-on-animal action or environmental harm. You wouldn't let a child assault another child, would you? But it would be crazy if we were equally compelled to intervene if a gorilla assaults another gorilla. And we wouldn't let kids hunger or thirst or freeze to death, yet that happens to animals in nature all the time. Not doing them harm is way different from being responsible for their well-being.