Relative Value of Carotene and Vitamin A Fed at Medium Levels in a Milk Replacer

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Abstract
Twenty-four, 1-day old male Holstein calves were fed initially 8 lb. of whole milk/day and gradually changed to a liquid milk replacer ration (virtually free of vitamin (vit.) A activity) during the first 7 days of age. Cn the 8th day, each calf was then fed the liquid milk replacer at 10% of its live weight and this allotment was increased on successive 7-day periods by a factor of 1.07,1.14 and 1.21, respectively. Beginning the 8th day, [beta] -carotene, (synthetic [beta] -carotene, gelatin beadlets) at one of 3 levels, 40 gamma, 80gamma, or 160 gamma, or vit. A(synthetic vit. Apalmitate, gelatin beadlets) 9 gamma, 12 gamma, 15 gamma, or vit. A (feeding oil), 9 gamma or 15 gamma, was fed daily/lb. of live weight for 3 successive 7-dav periods.: The rates of linear change of plasma vit. A on log intake were 4.98[plus or minus] 3.02 for carotene and 10.74[plus or minus]5.78 for both forms of vit. A. Based on linear regressions of response on log intake, carotene fed at the 40 gamma intake was calculated to be approximately l/8th as effective as vit. A in headlets; at the 80 gamma intake, l/llth and at the 160 gamma intake, l/l6th. Similar values for vit. A in oil were l/3rd and l/7th. The 2 forms of vit. A gave parallel responses, but the average magnitude of the response for beadlets was higher than for oil. The latter resulted in average plasma vit. A values of only 42% of those for beadlets.