Vitamin A is a fat soluble vitamin. Commercial feeds usually have this added at the proper level so there is no need to supplement the diet of rabbits and guinea pigs. In fact, because excesses of vitamin A can cause liver damage it is recommended that foods for rabbits and guinea pigs contain no more than is necessary to prevent deficiency. 12,000 iu per kilogram food is recommended for rabbits and guinea pigs. Beta carotene, a precursor of vitamin A, found in carrots and green vegetables, is less harmful than artificial vitamin A and is converted in the body to vitamin A when needed. Many chinchillas, however, differ from rabbits and guinea pigs in their inability to synthesise vitamin A from its precursor betacarotene and may require supplementation.
Grass is a good source of vitamin A and betacarotene.
B Complex vitamins are provided by the grains in the animals diet but the bulk are synthesized by good bacteria in the animals own gut. Rabbits and guinea pigs re-ingest part digested food in the form of soft, moist pellets produced in the caecum or hind gut which they eat directly from the anus without chewing. These help fulfil their need for the B complex vitamins as well as ensuring a healthy gut flora. Vitamin B supplementation is only normally required after blood loss or surgery; after scouring; when there are dental or dewlap problems which prevent the animal ingesting the caecal pellets or, occasionally, for impacted boars.
Feeding the caecal pellets from a healthy animal is a good way of restoring the B complex vitamin status and gut flora in a sick animal. Animals housed together will often 'share' their soft pellets with am ailing companion but if the animals are housed separately you may need to mix the caecal pellet with a little water and administer orally.
If no fresh caecal pellets are available, you should supplement the diet with B complex vitamins such as Biocare's Vitasorb B and a good probiotic. Vitamin C is important for the uptake of B Complex vitamins and should be fed at the same time.
Guinea pigs, along with humans, cannot synthesise vitamin C in their body and require a fresh supply of vitamin C every day. Adult guinea pigs require 10-15mg vitamin C per day, this is equivalent to 200-300mg per kilogram feed. Pregnant guinea pigs need twice this amount.
Green vegetables are a rich source of vitamin C with around 1mg vitamin C per 25gm. In contrast, you would need to feed 150gm of carrot, celery or raw beetroot to provide the same amount of vitamin C. Grass is a good source of vitamin C but do not feed grass cuttings which can ferment in the gut.
Even when your guinea pig food contains adequate levels of vitamin C, your guinea pig still needs the stimulation of fresh vegetables and grass in its diet. For pregnant animals or where the feed does not contain the necessary level of vitamin C, add vitamin C to the drinking water or sprinkle a little powder on cucumber or root vegetables.
Although rabbits and chinchillas can synthesise vitamin C in their own bodies, it is still sensible to supply a little extra during periods of stress or when supplementing with calcium or B complex vitamins where vitamin C is a co-factor in absorption.
Ester C is a buffered form of Vitamin C, kind to teeth and non-acidic. Biocare's Vitasorb C is a sublingual version of vitamin C and readily absorbed through the mucus membranes. Rosehips are a good source of vitamin C and a number of fruits such as Indian Amla (or Amalaki), Acerola Cherry, Acai and Camu Camu from the South American rainforests are quoted as having very high levels of vitamin C. Although quoted as having a high vitamin C content in many sources, some sources say that Amla (Embelica officinalis), also known as Indian Gooseberry, actually contains less vitamin C than some sources claim. Instead it's antioxidant action comes from the polyphenols it contains. One Ayurvedic site quotes a study at Bologna University in 2005 by Dr Paulo Scartezzini et al, which is probably the most up to date information on the subject.
NEW! At Galen's Garden we now have a new vitamin C supplement which consists of Amla and Acerola concentrated water soluble extracts. Each 20gm puffer pack contains around 4.5gm of vitamin C, enough vitamin C for a single guinea pig for 300-400 days! The powder can be added to drinking water, moist food or syringe feed mixes.
Vitamin D is another fat soluble vitamin. As with Vitamin A, both deficiency and excess can cause health problems. Feed for rabbits and guinea pigs should contain no more than 1,600 iu per kilogram food. 1,200 iu would be quite adequate.
Vitamin D is important for the utilisation of calcium. Lack of this vitamin can contribute to calcium deficiency. As vitamin D can be synthesised by the body from the UV light of the sun, access to an outdoor run in the summer can help maintain adequate levels of this vitamin whereas animals kept in sheds without access to much natural daylight might be prone to deficiency if the level in the food was low.
Vitamin E is important for cardiac health, fertility and maintenance of pregnancy in guinea pigs. Lack of it can lead to infertility, abortion, stillbirth and neonatal death. If your food contains less than 50mg vitamin E per kilogram food, particularly if you are breeding, you should supplement the diet with Vitamin E oil, Sublingual Vitamin E, wheatgerm, wheatgerm oil or Bemax.
Although less susceptible to infertility problems due to vitamin E deficiency, rabbits, like guinea pigs, can suffer from muscle weakness when vitamin E levels are low.