Sensitivity of Blood Plasma and Liver Vitamin A Concentrations and Vitamin A Depletion Time to Carotene and/or Vitamin A Intake

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Abstract
Blood plasma vitamin A concentrations and liver vitamin A concentrations obtained at slaughter upon the completion of a carotene and/or vitamin A supplement feeding period and vitamin A depletion time, from 5 experiments were used in this study. Average coefficients of variation across all experiments were 19.4% for plasma vitamin A, 9.2% for log (liver vitamin A), and 18.6%for vitamin A depletion time. Thus log (liver vitamin A) exhibited a smaller experimental error as a percentage of its mean than either plasma vitamin A or vitamin A depletion time. Average sensitivities of these criteria to carotene or vitamin A intake which was defined as the ratio of the linear slope of the re-sponse criterion on intake to the standard deviation of the criterion, Mandel and Stiehler, (1954), was 4.6 for plasma vitamin A on log (intake), 7.8 for log (liver vitamin A) on log (intake) and 0.1 for vitamin A depletion time on actual intake. Calculation of the sensitivity of vitamin A depletion time in terms of log (intake) gave a range of sensitivities between 0.3 and 23.9 which increased with the intake level. Depletion time was calculated to become more sensitive than plasma vitamin A at carotene intakes of greater than 110 [mu]g and vitamin A intakes of greater than 18 [mu]g and more sensitive than log (liver vitamin A) at carotene intakes of greater than 126 [mu]g and at vitamin A intakes of greater than 22 [mu]g.