Would you consider this to be animal abuse/neglect?

I was dog-sitting for my neighbors and I discovered that they only feed their full-grown golden retriever 3 measuring cups (actual 3 cups) of food per day. They also only give her one bowl of water for a day - and it's a small bowl. I've felt the dog, I can literally stick my fingers between her ribs. She's never had a bath or hair cut, so her fur is very long, yet I can still see her ribs through her fur. They don't walk the dog at all, and she sits outside all day on the deck. They have a fenced yard, BUT they keep her on a 3 ft leash all day. It's been raining non stop for the week and she's been sitting out there with no food at all, in the rain. She is fed her 3 cups of food once a day, and she has to eat very very fast to the point of choking it down. (When I was taking care of her, she would run for the food, eat it as fast as possible and then duck down to the floor like she was scared I'd hit her near the end of her meal). They are extremely impatient with her. I was told that the husband had once beaten the dog. She is very fearful of her owners. She rarely eats or gets fresh water. I was considering reporting the neighbors to the SPCA, but I'm not sure if they would classify this as abuse or not. I don't want to waste their time. I'm looking for serious answers, and advice or suggestions please. Thanks guys :)