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10 million IU of vitamin D3 for cows was great unless had vitamin D2 – July 2011

Vitamin D(2) impairs utilization of vitamin D(3) in high-yielding dairy cows in a cross-over supplementation regimen.

J Dairy Sci. 2011 Jul;94(7):3462-6.
Hymøller L, Jensen SK.
Department of Animal Health and Bioscience, Aarhus University, Faculty of Agricultural Sciences, Blichers Allé 20, PO Box 50, DK-8830 Tjele, Denmark.

Vitamin D exists in 2 forms that are important regarding vitamin D status and supply in cattle: vitamin D(2) (D(2)) and vitamin D(3) (D(3)). To become physiologically active, both D(2) and D(3) must undergo 25-hydroxylation in the liver. The resulting 25-hydroxyvitamin D(2) [25(OH)D(2)] and 25-hydroxyvitamin D(3) [25(OH)D(3)] are measured as indicators of the physiological vitamin D status of cattle.

The study used 14 Danish Holstein cows housed without access to sunlight.
The cows were orally administered 250mg (1.0 × 10(7)IU) of D(2) and D(3) in a cross-over design with 2 treatment groups and 2 study periods, rendering 4 treatments when carryover effects were taken into account: D(2) given first, D(2) given last after D(3), D(3) given first, and D(3) given last after D(2).

Two weeks elapsed between the treatment in the first study period and the treatment in the second study period. Blood samples were collected 0, 3, 6, 14, 17, 20, 23, 26, 40, 48, 70, 94, 166, and 214h after providing the oral bolus of vitamin to the cows.

Comparisons between plasma levels of the metabolites D(2), D(3), 25(OH)D(2), and 25(OH)D(3) over time were made by comparing areas under the plasma concentration curves. Oral administration of D(3) increased plasma D(3) (182.6±17.1 ng/mL; mean ± SEM) and 25(OH)D(3) (103.5±10.0 ng/mL) more efficiently than oral administration of D(2) increased plasma D(2) (49.1±32.6 ng/mL) and 25(OH)D(2) (27.9±2.1 ng/mL).

The D(3) given after an oral dose of D(2) was less efficient for increasing plasma concentrations of 25(OH)D(3) (61.2±12.0 ng/mL) compared with D(3) given without previous D(2) administration (103.5±10.0 ng/mL), whereas the plasma concentrations of D(3) itself were the same when given first (182.6±17.1 ng/mL) as when given after D(2) (200.0±123.9 ng/mL). The same occurred for plasma concentrations of D(2) metabolites both if D(2) was given first (49.1±32.6 ng/mL) and after D(3) (54.7±7.7 ng/mL).

In conclusion, D(3) given after D(2) is less efficient at increasing the plasma status of 25(OH)D(3) than D(3) given without previous D(2) administration.

Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

PMID: 21700032
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10,000,000 IU vitamin D3 raised vitamin D level in blood of cows to 183 ng (not toxic)

BUT vitamin D level not nearly raise as much if vitamin D2 had been given previously

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Weight: Cow = 1300 lbs, human = 180 lbs, so 10 million IU for cow would be 1,300,000 IU for human

Which is less than 2 million IU single dose toxic amount

Graph of dose vs week

See also VitaminDWiki