How do I fatten my guinea pig up a little I lnow its not healthy to have but he just seems to be on the smaller side for his age, he eats oxbow young guinea pig food and gets timothy hay all day everyday and eats fresh vegtables everyday

It sounds like he's eating all the right food - it might just be that he's naturally smaller than average. I had an underweight guinea pig and he was given supplements from the vet, which got his weight back up and made sure he was getting all the nutrition he needed.

If you haven't already, it might be a good idea to take your guinea pig to the vet to see what they recommend. Maybe he needs some sort of supplement, or a different kind of food? Also, maybe make sure that he's definitely eating the food that you give him! Only because sometimes my guinea pigs have buried their vegetables in their hay and bedding before!