Biopotency of vitamin E in lucerne meal for chickens.

In order to estimate the biopotency of vitamin E in lucerne/alfalfa meal in comparison to that of dl-alpha-tocopheryl acetate (dl-alpha-Ta; all-rac-alpha-Ta) a study was conducted with newly hatched White Leghorn male chicks. An increase in the vitamin E level in the liver and plasma, and the prevention of nutritional encephalomalacia (NE) were used as criteria for biopotency. After a vitamin E depletion period of one week posthatching, the chicks continued on a semipurified, vitamin E free basal diet without vitamin E supplementation, or were repleted with graded levels of that vitamin for six weeks, provided as extracted lucerne oil or as dl-alpha-Ta. High performance liquid chromatography (HPLC) with fluorescence detection was used for the analysis of the vitamin E homologues. The diagnosis of NE was based on clinical and histopathological observations. A significant increase (P < 0.05) in vitamin E content in the liver and plasma was observed in response to dietary supplementation with both vitamin E sources. The linear increase both in the liver and plasma storage assays was associated with a reduced incidence of NE. The disease was totally prevented by a dietary supplement of 7.50 and 5.40 mg vitamin E/Kg feed provided as dl-alpha-Ta or lucerne oil, respectively. The natural biopotency of the vitamin E in lucerne meal compared with that of dl-alpha-Ta in the liver and plasma storage assays and in the prevention of NE was 123, 105 and 99%, respectively, as calculated by the slope ratio technique.