I don't know much about the religious side of this discussion, but what I would like to know is, is the RSPCA going to prosecute the owners of this animal for allowing its unnecessary suffering? If not then why not.
They should be taken to court and at least fined, along with any other person who subjects an animal to deliberate neglect, which this is.
But having dealt with the RSPCA in the past the answer will be no. There has never been, in my opinion, such a completely useless animal charity.