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ARTICLE |
1 Department of Animal Sciences, University of Florida-IFAS, Gainesville 32611
2 Department of Statistics, University of Florida-IFAS, Gainesville 32611
3 ADISSEO, Acworth, GA
* To whom correspondence should be addressed. E-mail: mcdowell{at}animal.ufl.edu.
| Abstract |
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An experiment was conducted to evaluate bioavailability of 5 sources of vitamin A. It was hypothesized that some vitamin A products have protective coatings that are more resistant than others to rumen destruction and that such protection would result in higher vitamin A tissue concentrations. Fifty-three yearling Angus x Brahman cattle, consisting of 39 steers and 14 heifers, were stratified by BW and gender and randomly assigned to 6 high concentrate diet groups receiving either no vitamin A supplementation (control), or vitamin A supplemented from the following sources: Microvit A (ADISSEO, Acworth, GA), Rovamix A (DSM, Parsippany, NJ), Sunvit A, Lutavit A, and Microvit A DLC (ADISSEO). Vitamin A treatment groups were fed daily 80,000 IU retinol/animal in a low retinol concentrate diet (78.5% oats, 10% cottonseed hulls, 8% molasses, and 2% cottonseed meal) and a free-choice poor quality (low carotene) hay for 84 d. Every 28 d BW was determined and liver biopsies and plasma were collected and analyzed for retinol concentrations. All retinol treatments showed significant increases in liver retinol concentrations compared to control animals (P < 0.0001), which steadily decreased over time. At all collection times, Microvit A led to numerically greater concentrations of retinol in liver than did all other treatments. However, at experimental termination, there was no significant difference in liver retinol concentration among Microvit A, Rovamix A, Lutavit A, and Microvit A DLC diets. When liver retinol concentrations at all collection times were considered, Microvit A and Rovamix A appeared to provide the most bioavailable vitamin A.
Key Words: Bioavailability, Cattle, Retinol, Rumen Destruction, Vitamin A
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