β-Carotene Requirement for Adequate Plasma Vitamin a Level in Crossbred Calves

Ten crossbred calves (181.7±16.9d old) divided into two groups (I and II) on the basis of their body weight were fed on p-carotene deficient diet for 9 weeks so that their plasma vitamin A level decreased to less than 20 µg/100 ml. Thereafter, groups I and II were supplemented with 1 and 2 kg fresh berseem fodder respectively so as to provide approximately 40 and 80 mg β-carotene daily for a period of 11 weeks. Blood samples, collected weekly during depletion period and fortnightly during supplementation were analysed for β-carotene and vitamin A. A balance trial was conducted to assesss β-carotene, utilization at two levels of its intake. Plasma β-carotene and vitamin A decreased to 41.75±4.61, 37.93±8.82 and 17.27±3.30, 16.15±1.73 µg/100 ml in groups I and II, respectively, after 9 weeks of berseem withdraw! and increased to 259.40±41.64, 295.50±52.14 and 36.85±3.98, 32.87±2.64 µg/100 ml after 11 weeks of berseem supplementation. There was no linear correlation between plasma β-carotene and vitamin A and excess ?β-carotene was excreted in the faeces resulting in decreased β-carotene utilisation in group II, Supplementation of one kg fresh berseem in the ration amounted to total intake of 45.08 mg β-carotene/d and it was adequate to maintain the normal plasma level of vitamin A. The β-carotene requirement was calculated to be 0.35 mg/kg body weight in growing crossbred calves.