α-Tocopherol stereoisomers in beef as an indicator of vitamin E supplementation in cattle diets

These studies investigated the potential application of analysis of stereoisomers of α-tocopherol to discriminate between beef from animals raised at pasture or fed concentrates containing synthetic vitamin E. Muscle α-tocopherol levels were affected (P < 0.05) by diet with mean values of 2.63, 1.14, 2.43 and 1.77 μg g−1 muscle for beef from animals receiving pasture only (P), a barley-based concentrate with synthetic vitamin E (C), winter silage followed by summer pasture (SiP) and winter silage followed by summer pasture with concentrate (SiPC), respectively. Stereoisomeric analysis of α-tocopherol permitted discrimination between beef from the P/SiP, C and SiPC animals. In a comparison of Irish and non-Irish beef, Brazilian beef had higher (P < 0.05) α-tocopherol (8.13 μg g−1) than beef from Austria, England, France, Germany, the U.S. and Ireland (mean 2.51 μg g−1). Stereoisomeric analysis of α-tocopherol in non-Irish beef revealed supplementation with synthetic vitamin E in all samples, including the samples marketed as pasture-fed beef.