Vitamin A Requirements in Calves

Abstract

Six groups of four calves each were fed various levels of vitamin A, ranging from 32 to 1024 U.S.P. units per kilogram of body weight per day. Data were obtained on rate of growth, blood levels of vitamin A and liver storage. The results indicate that 32 units per kilogram of body weight just about cover the minimum requirement. At this level the calves grew fairly well and in most instances showed no evidences of night blindness. However, the blood concentration of vitamin A was low and there was little or no liver storage. Maximum growth was obtained on an intake of 64 U.S.P. units per kilo of body weight. The concentration of vitamin A in the blood was proportional to the intake until 512 units were given at which level maximal blood concentrations were obtained. Liver storage of vitamin A was quite variable. The majority of the calves receiving 64 units per kilogram or below showed no liver storage. In general, liver stores were quite low for calves receiving 32, 64 and 128 units per kilogram, whereas moderate amounts of vitamin A were found in the livers of those fed 256 and 512 units and large amounts in the 1024 units group. From the standpoint of both growth and liver storage the daily intake of vitamin A for young calves should be about 250 U.S.P. units per kilogram of body weight or 11,000 units per 100 pounds of liver weight. The vitamin A requirements in calves are of the same order of magnitude as in young rats and in infants.