USE OF A MODIFIED RELATIVE DOSE RESPONSE TEST OR VITAMIN A FRACTIONATION TEST FOR DETERMINING VITAMIN A STATUS FROM SERUM IN THE HORSE AND RABBIT.
AuthorJARRETT, SALLY HAYDON.
KeywordsVitamin A in animal nutrition.
AdvisorSchurg, William A.
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PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractMethods for assessing vitamin A status in the horse and rabbit were developed and evaluated using a modified Relative Dose Response Test (%RDR = A₄-A₀/A₄ X 100, where A₄ and A₀ represent four hours post-feeding and fasting serum total vitamin A levels, respectively) for horses and a Vitamin A Fractionation (VAF) Test monitoring serum levels of vitamin A palmitate, vitamin A acetate and retinol for horses and rabbits. In Experiment 1 (RDR test), 5 horses per treatment group were fed 0 (deficient), 10,000 (control) or 80,000 (excess) I.U. vitamin A palmitate daily, for 30 days. RDR Test was positive (>20%) for all horses receiving diets deficient in vitamin A and negative «20%) for all horses receiving control or excess diets. In Experiment 2 (VAF test), rabbits were fed varying dietary levels of vitamin A palmitate (ranging from 0 to 58000 I.U./kg feed) for up to 87 days. Percentages of retinol and vitamin A palmitate were reflective of vitamin A status. An approaching vita'min A deficiency or toxicity is indicated when percentages of vitamin A palmitate and retinol are more than 1 SD from the means observed for control rabbits (6.2±1.8 and 92.9±3.5, respectively). If a deficiency is approaching then percentage of vitamin A palmitate will be between 21% and 73% and percentage retinol between 8% and 21%. If toxicity is approaching then percentage vitamin A palmitate and retinol will be greater than 21% and less than 73%. Rabbit is normal if percentages are maintained within the ± SD of the mean. Experiment 3 (VAF test) was conducted using the same horses and conditions as in Experiment 1. After 30 days on treatment, percentages of retinol and vitamin A palmitate were significantly lower and higher (P<.05) than controls, for deficient and excess horses, respectively. The percentages of vitamin A palmitate and retinol in deficient horses were intermediate between values observed in horses from the other two treatment groups. If percentage retinol is between 45% and 65% and percentage vitamin A palmitate is between 31% and 45% the horse is approaching deficiency. If the percentage retinol is less than 45% and and vitamin A palmitate is greater than 45%, then the horse is probably approaching toxicity. Results suggests that both RDR and VAF tests can be used to determine vitamin A status before appearance of overt signs of deficiency occur, however only the VAF test is suitable for detecting toxicity.
Degree ProgramNutritional Sciences