Shadow the guinea pig, by RaGardner4 / Flickr
Guinea pigs in hay, by linuxchic / Flickr
Guinea pigs are unique in their lack of ability to synthesize vitamin C, therefore have a dietary requirement. They are one of the few non-primate mammals with a vitamin C requirement. Because of this trait, guinea pigs are often used to the study scurvy, a disease that results from a vitamin C deficiency. It is important to feed commercial guinea pig pellets because they all contain vitamin C, whereas rabbit, mouse, or rat food won't probably contain it, and consequently they should be avoided . You can supplement their diet with fruits and green leafy vegetables to provide extra vitamin C. Alfalfa hay and alfalfa-hay based products can lead to kidney stones in adult guinea pigs. Therefore, it is best to feed Timothy hay and Timothy hay based pellets.