I personally hate combat infamy in this game. I may be one of the few, but I can't stand all of the focus on combat. Especially the contracts. I thought I was creating a park, not an arena. That being said, lots of people do like it. So I guess it's good for them.
To get on topic, I live next to a local aquarium. I go there all of the time. I do admit, that I can't say that the electric eel, or sharks chomping down on fish makes much of a difference to how I view them. To me that's feeding time. It's all part of the experience. What does impress me is when care and detail go into the enclosures.
I don't think goats adding to combat infamy is a great idea. I'd rather have some sort of reward system for carnivores eating appropriate food items or living in correct exhibits. A more natural enclosure or diet truly adds to the zoo experience, enabling us to see the animals in their natural setting. In some cases goat chomping may provide this. In others it may be fish feeders. For still others it may be something else entirely.
I do think that foundation of the OP where carnivores can increase in rating is good idea; however, I'm not sure goats providing combat infamy is the sole way to achieve this.