Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: 4/20/1999
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Recent trends in the nutritional management of calves have promoted supplementing milk replacers with vitamin A at substantially greater levels than recommended by NRC. Calves were fed pooled colostrum after birth and thereafter for 4 wk a milk replacer providing 0, 1700 (NRC requirement), 34000, or 68000 IU of vitamin A/d to evaluate effects of dietary vitamin A on retinoid metabolism. Plasma retinol, retinoic acids (RA) and RRR-alpha-tocopherol (aT) were determined by HPLC, and retinol binding protein (RBP) by ELISA. Blood samples were collected at birth and weekly for 4 wk. Plasma 9,13-di-cis-, 9-cis-, and 13-cis-RAs, and RBP were substantially higher in calves fed 34000 and 68000 IU of vitamin A/d. Overall, retinol concentrations were correlated positively with all isomers of retinoic acid from 1 to 4 wk of age and with RBP from birth to 4 wk of age. Retinol concentrations were correlated negatively with aT and unrelated to RRR-gamma-tocopherol concentrations, at 4 wk of age. These results indicate that excess dietary vitamin increases plasma concentrations of biologically active isomers of retinoic acid and reduces the bioavailability of vitamin E (aT), an essential antioxidant.