Dietary supplements are nutrients (minerals and vitamins) that are artificially synthesized by man. These nutrients are added to your guinea pig's daily, weekly or monthly diet to maintain proper nutrition. The ideal natural diet does not require supplements, but it is rare that ideal situations are created for humans or their pets.
Fortunately for pet owners, laboratories and pet food companies have gone to great lengths to design foods that meet pet requirements. Commercial brands of pet food are formulated with a proper balance of nutrients, without the possibility of overdose or error.
Prepackaged guinea pig pellets originally designed for use in laboratories take the guesswork out of nutrition. Pellets provide all the nutrients your guinea pig needs except for vitamin C. See below for more information on vitamin C.
Your guinea pig will easily consume all the other nutrients -- except for vitamin C -- he needs in his daily diet. The most important thing to remember is that your guinea pig requires vitamin C and does not have the necessary enzymes to make or store enough vitamin C to survive on his own. This vital nutrient must be added to his diet in fresh foods or by a supplement in his food or water.
Vitamin C deficiency (scurvy) is a severe disease; muscle, bone and soft tissues lose strength due to the body's inability to produce and maintain collagen. The first signs of scurvy might be difficulty walking, bleeding gums, slobbering, skin conditions, or swelling joints. If left untreated, scurvy will result in death.
You must be certain that your pet is getting his daily requirement of 15-30mg/day of vitamin C. This is easily obtained with a combination of prepared pellets and fresh foods (such as kale, broccoli, strawberries, oranges, etc.). If you are unable to provide fresh food to your guinea pig, you must provide vitamin C in a dietary supplement. While pellets are balanced in nutrition, they should not be relied upon to be the only source of vitamin C. It is too risky as vitamin C breaks down rapidly in pellets.
Because it is a major issue for guinea pigs, vitamin C supplements are readily available. You can also use vitamin C tablets and grind them up. Measure these supplements to the proper amount and add them to tasty food or to the water source.
If you add it to the water source, there are some things to know. Vitamin C is water soluble, unlike the fat soluble vitamins (A, D, E and K) which need a dietary fat to be broken down, water soluble vitamins (B and C) will break down in water. Since you have to change your guinea pig's water daily, you must add vitamin C each time the water is changed. Tap water often contains large amounts of chlorine that can render Vitamin C inactive. If you have a large bottle or more than one guinea pig, it might be harder for you to determine just how much each guinea pig is getting.