Guinea pigs are herbivores, and their diets are comprised totally of hay, pellets, water, and fruits ( like oranges ) and veggies ( like green peppers ). Guinea pigs do not eat meat or dairy of any kind, nor nuts or seeds. They cannot manufacture Vitamin C on their own, but it is absolutely necessary to survive. Generally, pigs will get enough Vitamin C through a balanced proper diet, but Vitamin C tablets are an excellent way to ensure they get enough.
HAY: Unlimited, high-quality grass hay is an essential building block for your pig’s health. Not all hays are the same! Be sure to check the hay you are buying for your pig is timothy hay or orchard grass, not alfalfa (which can be fed to younger guineas, pregnant guineas, or malnourished guineas, but should be a treat for typical guineas due to its high calcium content). Unlimited is the key word here -- there is no such thing as too much hay!
Oh - OHH! I didn't see you there! How embarrassing, you must think I'm such a pig . . . <3
PELLETS: Remember the last time you were in the cereal aisle searching for a hearty, wholesome staple to start your day? Your eyes may have been drawn to the flashy colors of some dry cereals, but you know deep down those chemically-dyed bits and sugary concoctions may look neat, but will negatively affect your health. Unfortunately, guinea pig pellets are created in the same exact way. Beware (and steer totally clear of) any pellets with nuts, seeds, or colored bits -- even if they claim to be nutritious bits of vitamins. The only pellets you should ever feed your guinea pig are plain, dye-free, high-quality pellets. GuineaLynx has a great resource for finding high-quality pellets here: http://www.guinealynx.info/pellets.html
Safe (left) v. unsafe pellets. Guinea pig pellets should be plain and high quality; many big-box pet stores stock mixes featuring nuts, seeds, dried fruits, yogurt, or dyes -- all of these should be avoided.
WATER: Fairly self-explanatory here -- give your piggies fresh, cold water, changed daily, kept in a drip bottle to prevent contamination. Never add supplements to their water; Vitamin C, for example, destabilizes in water, and because some pigs drink very little water and some drink much more, you will not be able to accurately determine how much of the supplement they are actually consuming.
FRUITS AND VEGGIES: While water, hay, and pellets should be the bulk of your cavy’s diet, you can also feed fresh (never canned) fruits and veggies. Vegetables should outweigh fruits, due to the high sugar content of most fruits, and green veggies are generally best. Lettuces (romaine, green or red leaf lettuce, but NEVER ICEBERG) are great choices, along with bell peppers, carrots, apple, cucumber, parsley, cilantro, melons, and berries are our personal go-tos. Not all guinea pigs have the same tastes and preferences; my piggie Rosie is very picky and will not eat most fruits or veggies, but my family’s piggie Elli will eat just about anything. Do not feed cruciferous vegetables, as they produce gas, and guineas cannot pass gas on their own -- this can quickly lead to death.
VITAMIN C TABLETS: After a health scare with Rosie, I began supplementing her diet with two Oxbow Vitamin C tablets a day (a very popular choice for these tablets). She fully recovered and seems to be even better than before, and many people have had similar experiences with their piggies. Even if you think your pig is receiving enough Vitamin C daily through their hay, pellets, and snacks, the tablets may be a sound choice anyway -- after all, don’t you want the absolute best for your fluffball?!