Effect of Prolonged Feeding of Raw Carrots on Vitamin A Content of Liver and Kidneys in the Dog

Abstract

Summary

The vitamin A content of the liver and kidneys of dogs fed fresh carrots is greater than that found in dogs on a meat and boiled rice diet. The level of the vitamin A concentration in the liver and kidneys is approximately 20 vitamin A animal units. Continued feeding of carrots or addition of cod liver oil apparently does not increase the vitamin A content above this level. The spectroscopic examination indicates that the carotene from the carrots was transformed to vitamin A.

The function of carotene in nutrition has been established.^1-4 The advisability of feeding large amounts of raw carrots over a prolonged period of time is still questioned. Carotinemia has been observed in the dog, 5 and in man. 6 Investigations of Moore, 2 Capper, 7 and Drummond 8 have shown that conversion of carotene to vitamin A takes place in the livers of vitamin A-free rats or fowls. Olcott and McCann 9 later confirmed these observations and further concluded that this change may take place in vitro if incubated with fresh liver tissue. Rea and Drummond 10 failed to obtain a carotinase in liver preparations from vitamin A-free rats and further obtained no increase in vitamin A content of cat livers after carotene administration.

Table I presents the results obtained by feeding dogs fresh carrots over a prolonged period of time (2 to 8 months). Five of the animals received a diet of meat, boiled rice and fresh carrots; 3 received a similar diet with the addition of 10 cc. of cod liver oil daily, and 2 were deprived of both carrots and cod liver oil. The 2 dogs receiving only meat and boiled rice succumbed at 15 and 49 days. Previous to this their appetite became sporadic, there was marked discharge from the nose and eyes and in all the symptoms were those of distemper. The remaining dogs continued to maintain or gain in weight and appear healthy and vigorous. They were killed and autopsied at varying times. No signs of carotinemia were observed in any of the dogs. The liver and kidneys were removed at necropsy and prepared for vitamin A estimation by the method of Moore. 2

The colorimetric estimation was carried out by the method of Norris and Danielson. 11 The dilutions of the extracted tissue oils were made so that the readings were below 2 blue Lovibond units.