Effect of Two Levels of Intake of a Vitamin a Depletion Ration on Some Blood Constituents and Deficiency Criteria in the Dairy Calf

Abstract

Summary Ten pairs of 36-day-old calves were fed a vitamin A depletion ration at two levels of intake, low and high, until the blood plasma vitamin A values decreased to less than 4.0 γ % for two consecutive 7-day periods. This resulted in a 7-day increase in body weight of 7.1±1.5 and 11.0±0.4lb. for the low and high levels of intake, respectively. Over-all, plasma carotenoids and vitamin A were found to decrease while whole blood and plasma ascorbic acid exhibited no change. None of these constituents were affected by the level of intake of the depletion ration. Hemoglobin was observed to decrease in the calves on the low level of intake of the depletion ration but no change was found for the calves on the high level. Heart rates of animals on the high level of intake averaged 20 beats per minute higher than those on the low level of intake, whereas rectal temperatures and terminal spinal fluid pressures were unaffected. Among the histological changes, only the frequency of occurrence of squamous metaplasia in the interlobular ducts of the parotid gland was significantly greater in the high level group.