Seven ways to feed your hungry guinea pig

Guinea pigs are herbivores (plant eaters). They don’t tolerate high carbohydrate or fatty diets, so don’t feed them “fiesta” or “gourmet” pellet mixtures, which have seeds, nuts or dried fruits.
Give your guinea pig plenty of hay. Timothy hay is the best choice; alfalfa does not have the proper ratio of calcium to phosphorus. Pellets aren’t an adequate replacement because they don’t provide enough long fiber to keep the intestines in good working order.
Keep your guinea pig sleek. Pellets are high in protein – and calories. So, if you don’t want an aging pet to get fat, cut down on the amount of pellets while continuing to feed timothy hay.
Chewing is healthy. Another reason to hand out the hay is that chewing hay keeps the animals’ teeth healthy. Guinea pig teeth, like rabbits’ teeth, grow throughout their lives and need to be ground down. While treats and chew sticks make good toys, they don’t wear down the teeth properly.
Make sure your pet has plenty of fresh, clean water. You can add Vitamin C to the water bottle, which should be covered with foil because the vitamin degrades when exposed to light. Water should be changed daily, and containers cleaned to prevent build-up of algae and bacteria.
Use only pellets made specifically for guinea pigs, which contain vitamin C. These animals don’t produce the vitamin, and their diet has to provide it. Make sure to store the pellets in a cool place because vitamin C breaks down rapidly in heat and with time; most of it is gone 90 days after the pellets are milled.
Veggies are a must. Fresh vegetables - kale, escarole, endive, spring mixes, carrot tops, parsley, cilantro, and spinach - can help maintain a healthy intestinal tract while providing lots of vitamins and minerals. When you start to add vegetables to your pet’s diet, offer only one type at a time, so if there are digestive upsets you’ll know what’s causing them.