|Ametaj, Burim - IOWA STATE UNIV, AMES|
|Franklin, S - SD STATE UNIV, BROOKINGS|
Submitted to: American Dairy Science Association Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: July 27, 1998
Publication Date: N/A
Technical Abstract: The practice of supplementing milk replacers fed to calves with high levels of vit A has raised concerns regarding the effect of excess vit A on the bioavailability of vit E. Using a 4x2 factorial experiment, we evaluated the effects of 4 dietary levels of vit A (0, 1700, 34000, and 68000 IU/d as retinyl acetate) and 2 forms of vit E (d-alpha-tocopherol and d-alpha-tocopherol acetate at 100 IU/d) on lipoprotein (Lp) associated alpha-tocopherol (aT) in plasma from milk replacer-fed calves from birth to 5 wk of age. Plasma Lp fractions (VLDL, LDL, HDL and VHDL) were isolated and associated aT conc were determined. Amounts of aT associated with total Lp (tLp) and HDL, VHDL, LDL and VLDL fractions were unaffected by the form of vit E fed to the calves. Alpha-T conc associated with tLp and HLDL, VHDL, LDL and VLDL fractions increased with age and were maximal at wk 5. At birth, 50% of tLp-associated aT was in the VHDL fraction, with only 9% remaining in this fraction by 5 wk postpartum. The main carrier of aT from wk 1-5 was the HDL, with LDL and VLDL transporting 15 and 3% of the aT, respectively. The amount of vit A profoundly affected the conc of Lp-associated aT. The tLp-associated aT conc were lower in calves fed 34000 and 68000 IU/d of vit A than in control calves fed 0 IU/d of vit A at 3 wk postpartum. By 5 wk postpartum, calves fed vit A at 1700 IU/d also had lower tLp-associated aT conc than control calves. During this period, the amount of aT associated with HDL, VHDL, and LDL was similarly affected by dietary vit A, with lowest aT conc occurring in calves fed 68000 IU of vit A/d. At wk 1 postpartum, calves not fed vit A had the lowest aT conc in these fractions. In conclusion, the form of dietary vit E had no effect on conc of aT present in tLp or its fractions.