I took in a guinea pig that was very very thin. He looks no older than two years old. The only reason I never took him to the vet is because he was never lethargic, always had a high energy. I've been feeding him cavy performance food (the young oxbow kind) giving him unlimited Timothy with orchard and alfalfa as well. I give him at least 5 baby carrots a day. I'm noticing that his pee has become incredibly strong though. I cleaned his cage yesterday morning and by last night he had stunk up the room. I work at a pet store so I know what normal guinea pig pee smells like. The only way I know how to explain the smell is that it smells sour. I know that they excrete their excess vitamin c so I thought maybe with all of this food that could be causing the smell? I couldn't find a single thing on it though except on ONE website which said it COULD be a uti. They didn't give mete impression that it was an emergency though. He also does have any other symptoms of a stone or uti. Does anyone know what is causing this awful strong smell?!?