Once you have obtained the proper housing for your guinea pig (see suggested links at the end of this article), you need to educate yourselves as to their proper diet. Good-quality commercial guinea pig pellets and fresh timothy hay should make up the bulk of your pet’s diet. Guinea pigs have continuously-growing teeth, and unlimited timothy hay will help keep your guinea pig’s teeth in good shape and will regulate his digestive system. Quality guinea pig food pellets are nutritionally complete and 1/8 cup daily (per pig) is the recommended amount; discard any leftover pellets after 24 hours and replace with fresh pellets.
The ASPCA recommends offering small amounts of fresh fruit and vegetables to your guinea pigs every day. Guinea pigs cannot manufacture Vitamin C as other animals do, so you need to offer them produce that is high in vitamin C every single day. A quarter slice of orange is fine, but kale, dandelion greens and strawberries are also high in vitamin C. Other produce that is safe and healthy for piggies include grapes, pears, apple, sweet potatoes, cucumbers, corn, peas, and carrots. Half a handful of veggies and a small slice of fresh fruit per pig is plenty. Introduce new fruits and veggies gradually to avoid digestive upsets. If your guinea pig develops loose stool, cut back on the amount of fresh produce for a few days, then gradually reintroduce it in very small portions. Be sure to clean up any leftover fresh food before it spoils.
Use a ceramic food dish instead of a plastic one, as the plastic ones are easily overturned and can be chewed up. Use a wide, shallow bowl as guinea pigs like to place their front feed on the bowl while eating, and a wide, shallow bowls lessens the likelihood that the piggie will overturn the bowl. Food bowls need to be placed away from the guinea pig toileting area, and need to be spot cleaned during the week and washed with soap and water (and dried!) once a week. Fresh, clean water should be available at all times; use a water bottle with a drinking tube and change the water daily.
Time for a treat? Commercial treats marketed for guinea pigs and other small pets are generally loaded with artificial sweeteners such as high fructose corn syrup or sucrose; these provide little to no nutritional value, lots of empty calories and are not good for the pet’s health and weight. Save yourself some money and offer your piggie treats of small amounts of fruits and vegetables. For a special treat, you could offer a generous pinch of rolled oats or some SHELLED sunflower seeds. NEVER give guinea pigs unhulled (unshelled) sunflower seeds or unshelled pumpkin seeds, as these are a choking hazard.
Multivitamins and mineral wheels are both low-priority items: if you’re feeding your guinea pig a proper diet they won’t need either of these items. The glues and adhesives that hold mineral and salt wheels together may not be harmful but at the least they are not healthy. The bleaching process used in manufacturing the ‘white’ salt wheels adds unnecessary chemicals into your pig’s diet. This author has never known of a guinea pig who has become ill from a mineral or salt wheel but neither are they basic necessities.
Guinea pigs have aridacular (constantly-growing) teeth, just like other rodents (and rabbits, although rabbits are not rodents, they are lagomorphs). Your guinea pig is going to need something to keep those teeth worn down - branches and twigs from untreated trees will work, as will any small piece of wood that has not been chemically treated.
If you are looking to adopt a guinea pig(s), check with local shelters - the Humane Society of Greater Dayton regularly has guinea pigs available for adoption, as do Robyn's Nest Rescue in Miamisburg, Ohio.