title: Dietary vitamin A modulates the concentrations of RRR-alpha-tocopherol in plasma lipoproteins from calves fed milk replacer.
abstract: The practice of supplementing milk replacers fed to neonatal calves with high concentrations of vitamin A has raised concerns regarding the effect of excess vitamin A on the bioavailability of vitamin E. A 4 x 2 factorial experiment evaluated the effects of four dietary amounts of vitamin A [0, 1.78 [National Research Council (NRC)(6) requirement, control], 35.6 and 71.2 micromol daily as retinyl acetate] and two forms of vitamin E (RRR-alpha-tocopherol and RRR-alpha-tocopheryl acetate, 155 micromol daily) on plasma RRR-alpha-tocopherol and RRR-gamma-tocopherol and RRR-alpha-tocopherol associated with plasma lipoproteins (Lp) from milk replacer-fed Holstein calves from birth to 28 d of age. The VLDL, LDL, HDL and very high-density lipoprotein (VHDL) fractions were separated by ultracentrifugal flotation, and the amount of vitamin E associated with each fraction was determined by normal-phase HPLC. The amount and distribution of RRR-alpha-tocopherol in Lp fractions were unaffected by the form of dietary vitamin E. Plasma and Lp RRR-alpha-tocopherol concentrations increased with age (P < 0.0001) and were maximal at 28 d of age. Concentrations of RRR-alpha-tocopherol associated with Lp were 25% (P < 0.01) to 39% (P < 0.0001) lower in calves fed 35.6 and 71.2 micromol of vitamin A daily than in control calves at 28 d of age. The RRR-gamma-tocopherol concentrations were unaffected by dietary vitamin A (P >/= 0.05). In conclusion, dietary vitamin A modulated the amount and distribution of RRR-alpha-tocopherol in the circulation of milk replacer-fed neonatal calves. Because of the essential antioxidant role of vitamin E, the health-related consequences associated with the depression of the LP RRR-alpha-tocopherol concentrations in calves fed vitamin A at 35.6 and 71.2 micromol need to be investigated.
authors.affiliation: Department of Animal Science, Iowa State University, Ames, IA 50011, USA.
authors.forename: B N
authors.initials: BN
authors.lastname: Ametaj
authors.forename: B J
authors.initials: BJ
authors.lastname: Nonnecke
authors.forename: S T
authors.initials: ST
authors.lastname: Franklin
authors.forename: R L
authors.initials: RL
authors.lastname: Horst
authors.forename: W R
authors.initials: WR
authors.lastname: Bidlack
authors.forename: R L
authors.initials: RL
authors.lastname: Stuart
authors.forename: D C
authors.initials: DC
authors.lastname: Beitz
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004032:Diet; D019587:Dietary Supplements; D005526:Food, Formulated; D008074:Lipoproteins / Q000032:analysis / Q000097:blood*; D013237:Stereoisomerism; D014018:Tissue Distribution; D014801:Vitamin A / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology*; D014810:Vitamin E / Q000032:analysis / Q000097:blood / Q000493:pharmacokinetics*
chemical_list: D008074:Lipoproteins; D014801:Vitamin A; D014810:Vitamin E