Guinea pig food primarily consists of high-quality hay, which is essential for their digestive health. Timothy hay is a popular choice, providing necessary fiber that helps prevent obesity and dental issues. In addition to hay, guinea pigs require a small amount of fresh vegetables and fruits for vitamins, particularly vitamin C, which they cannot produce on their own. Commercial guinea pig pellets are also available and should be included in their diet. These pellets are specially formulated to meet their nutritional needs. It's important to avoid foods high in sugar or fat, as these can lead to health problems in guinea pigs.