Hypovitaminosis C in The
Guinea Pig
Robert Ness, DVM
Midwest Bird & Exotic Animal Hospital
1923 S. Mannheim Rd Westchester, IL 60153
Guinea Pigs (Cauia porcellus), primates (including man), and certain species of fruit bats require exogenous vitamin C. These animals lack or are deficient in the microsomal enzyme L-gulonolactone oxidase, which is necessary for the conversion of D-glucose to L-ascorbic acid. A deficiency of ascorbic acid leads to impairment of collagen synthesis due to a defective hydroxylase reaction in the formation of hydroxyproline and hydroxylysine. In addition, ascorbic acid is involved in the metabolism of cholesterol, carbohydrates, and amino acids. A deficiency of dietary ascorbic acid leads to the clinical syndrome known as scurvy or scorbutism.
Commercial Guinea pig diets are formulated with supplementary vitamin C. The typical guinea pig pellet contains ascorbic acid at approximately 800mg/kg diet at the time of milling. Factors such as dampness, heat, and light contribute to reduce the vitamin C content during storage. Even pelleted diets stored under optimal conditions lose their potency within 90 days of milling.
Since formulated diets rapidly lose their ascorbic acid potency, further supplementation is necessary. Citrus fruits, cabbage, and kale are rich in ascorbic acid. One hundred grams of fresh kale contains about 125 mg of vitamin C. A single cup of fresh cabbage provides approximately 60 mg of vitamin C. The average Guinea pig can obtain his daily supplementation of ascorbic acid from one half cup of cabbage or kale or one quarter of an orange. Alternatively, vitamin C can be added to the drinking water at a dosage of 50 to 100 mg/cup. Human vitamin C syrup or tablets are preferred over multivitamin drops to avoid potential toxic overdose of other vitamins. The solution must be prepared fresh daily, preferably in distilled or deionized water. This is necessary since vitamin C is water soluble as well as susceptible to oxidation by copper from water pipes. Direct oral supplementation of ascorbic acid at 10 to 30 mg/kg body weight guarantees adequate daily intake of vitamin C. This supplementation can be given in a small amount of juice or other flavored drink to increase palatability.
Guinea pigs fed diets totally deficient in vitamin C show signs of clinical disease within two weeks. Conditions of pregnancy, lactation, rapid growth, stress, and concomitant disease increase the vitamin C requirements, thereby resulting in a more rapid onset of scurvy when exposed to this dietary deficiency. Early clinical signs of scurvy include rough hair coat, anorexia, dehydration, delayed wound healing, and increased susceptibility to infection. Some cases of unexplained anorexia may involve further manifestations of scurvy expressed as subtle periodontal disease and temporomandibular inflammation. In addition, other dental abnormalities may occur in young animals, such as brown discoloration of teeth and gradual migration of teeth out of alignment. As the disease progresses, gingival and periarticular hemorrhages occur. These changes are manifested as bruising, swelling, and lameness. Further progression results in swelling and hemorrhage of the costochondral joints. Radiographic lesions include enlarged costochondraljunctions, abnormal epiphyseal growth centers, and pathologic fractures. The young, rapidly growing animal is most likely to present with the classical lesions of abnormal bone formation, secondary bacterial pneumonia, and enteritis. Death from starvation, hemorrhage, or secondary infection often follows within three to four weeks.
Upon necropsy, gross lesions include bony abnormalities, and hemorrhaging. Widespread hemorrhage occurs in subcutaneous tissues, muscle, intestines, costochondral junctions, and subperiosteum. Other necropsy findings include deformed bones, separation of epiphyseal junctions, pathologic fractures, and loose teeth.
Treatment for scurvy involves ascorbic acid supplementation as well as attention to any underlying or secondary infections. Exogenous vitamin C must be administered orally or subcutaneously at a dose of 25 to 50 mg/kg daily. Fluid therapy and nutritional support are often required since the majority of these animals are anorectic. Prophylactic antibiotics may be indicated for five to seven days to treat or prevent secondary bacterial infections. Once the patient has recovered clinically, the dose of vitamin C can be reduced to maintenance levels as described above.
The actual incidence of scurvy in private practice is unknown, since the condition itself is very likely underdiagnosed. Although it is a fact that Guinea pigs require supplemental vitamin C, the importance of it in common syndromes is often overlooked. Many of the commonly encountered Guinea pig diseases have an underlying subclinical scurvy. Any differential diagnosis for lameness, diarrhea, or anorexia must include hypovitaminosis C. Routine vitamin C supplementation should be incorporated in the therapeutic regimen of Guinea pig syndromes.
References: Cheeke, P.R.: Rabbit Feeding and Nutrition; Chapter 19 - Nutrition of Guinea Pigs, p.349, Academic Press, Inc., Orlando, FL 1987. Clarke, G. L., Allen. A. M.. Small, J. D., and Lock, A., Subclinical Scurvy in The Guinea Pig. Veterinary Pathology, 17:40-44, 1980. Collins. B. R., Common Diseases and Medical Management of Rodents and Lagomorphs, in Exotic Animals. Edited by Jacobson, E. R., and Kollias, G. V., Churchill Livingstone, New York, NY, pp. 286288, 1988. Harkness, J. E., and Wagner, J. E., The Biology and Medicine of Rabbits and Rodents. (Third Edition). Lea & Febiger, Philadelphia, PA, pp. 142-143, 1989. Manning, P. J.. Wagner, J. E., & Harkness, J. E.: Biology and Diseases of Guinea Pigs. In Laboratory Animal Medicine, edited by Fox, J. G., Cohen, B. J., and beow, F. M. Academic Press, New York, NY, pp. 169-171, 1984.