Definitely hay. Timothy and Medowgrass hay are great when they're an adult. Alfalfa is good for youngsters. Alfalfa hay is the best when they're under six months of age. But after that, we don't want to offer it anymore because it's really high in calcium, so it can cause them to have bladder stones or just become obese because of the extra nutrients in it.

Apples and grapes?

Very small amounts of apples are fine, but in general, fruits have a lot of sugar, which can upset their GI system. So tiny amounts infrequently are okay.

Bananas and strawberries?

Very tiny amounts.

Oranges and watermelon?

Probably not. There's a lot of water in it, but a lot of sugar too. I would avoid that. When they have too much sugar, it throws off the bacteria in their GI systems that are in there, and they need the bacteria as their fermentation vat in what's called their cecum. That helps them absorb the nutrients they need and eliminate the ones they don't. So the sugar gets that all out of whack, and it can cause them to have looser stool, diarrhea, and things like that, which can be pretty dangerous when they get dehydrated. Some guinea pigs are okay with a whole slice, and some can only have a little corner piece. So it depends on the pig.

Vegetables, like celery, tomatoes, and broccoli?

Broccoli's okay. Celery has a lot of water, so they can have it in moderation. The veggies are better because they're lower in sugar. Some of the veggies are good because the guinea pigs do need vitamin C. In general, focus more on peppers and things like that. Broccoli leaves are really good too. Green, yellow, and red peppers are good. Focus on the green and red ones more. Chopping those up and giving like a quarter cup of that a day will be good for their vitamin C levels. Morning or evening are good times to give a little tidbit of veggies and pellets at night. Alternate those so that you can see if your guinea pig is still eating and they're excited about eating. You'll be able to monitor it better that way.

Hay all the time is good, but they can overeat pellets, fruits, veggies, biscuits, and things like that. So moderate that, but leave the hay all the time.

Oxbow makes little hay biscuits. Otherwise, certain veggies, like peppers, are good for occasional treats.

One of the brands, Oxbow, has a website you can order from. Otherwise, we have some at our clinic. Some pet stores have a variety of brands, so just ask your veterinarian which brands you should go for and which you should avoid.