Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract only
Publication Acceptance Date: 4/18/1998
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: The relative dose response (RDR) assay has been used to determine the vitamin A status in humans when a liver sample is unattainable. The objective of this study was to determine the ability of the RDR assay to detect vitamin A deficiency in calves. Holstein bull calves were fed colostrum at 5% of their body weight at birth. Calves were assigned to 1 of 4 levels of retinyl acetate supplementation at 0, 1700, 34,000 or 68,000 IU daily. Calves remained on trial through 28 days prior to the RDR assay. Liver biopsies were performed after 28 days and blood samples were obtained via jugular venipuncture before receiving a dose of 1700 IU of retinyl acetate in milk. Blood samples from calves subsequently were obtained at 4, 6, 8 and 20 hr post-dosing. Plasma was harvested and stored at -20 C until analysis of retinol concentrations by HPLC. Vitamin A supplementation influenced (P=0.0036) the RDR at 8 hr post-dosing. The RDR indicated that all calves supplemented with 34,000 or 68,000 IU daily of retinyl acetate had adequate vitamin A status even though mean plasma vitamin A concentrations were 12.5 and 11.7 micrograms/dl, respectively, The RDR assay indicated that 44% of the calves supplemented with 0 or 1700 IU of retinyl acetate daily for 28 days were deficient in vitamin A. The RDR assay may prove a more useful tool for determining vitamin A status of cattle than single plasma samples.