Obviously pigs need human companions as well, and can either be kept inside in an indoor cage or outside in a hutch. Although care should be taken with outside pigs as in winter they can chill easily and in summer can suffer with the heat. Apart from providing guinea pigs with the correct cereal based diet guinea pigs need vitamin C as they cannot produce this vitamin in thier bodies. Without this they will become very ill and are likely to develop scurvy. It is easy to prevent this by feeding fresh fruit and vegetables every day. Hay should also be always available as is an important part of their diet, a very good source of roughage and helps maintain their gut and their teeth.