My dog Rubi has 1-month old puppies. They can eat liquid food and they have their teeth already. The problem is that when they try to drink milk from their mother, she gets mad and bites them alot like if she were killing a cat. She hasn't killed one, but I am really scared that she might. The puppies try to get milk from were she doesn't have any. She hasn't had that problem because when they were little she took good care of them. I even have to tie her up when I give the puppies liquid food because even though she has her own she gets mad at the puppies and doesn't want them to eat it only her. PLEASE HELP!!

What breed are they, how old is Rubi and is this her first litter?

Rubi is a bull terrier and this is her first litter.