Bioavailability of Vitamin A (Retinol) Sources for Cattle

An experiment was conducted to evaluate bioavailability of five sources of vitamin A (retinol). Fifty-three yearling Angus  Brahman cattle, consisting of 39 steers and 14 heifers, were stratified by BW and gender and randomly assigned to six 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) for 84 d. Every 28 d body weight 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 experiment 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.