THE INCORPORATION OF75Se-SELENITE INTO DYSTROPHOGENIC PASTURE GRASS: THE CHEMICAL NATURE OF THE SELENO COMPOUNDS FORMED AND THEIR AVAILABILITY TO YOUNG OVINE

Abstract

An investigation was conducted on the nature of selenium compounds formed in brome grass obtained from a muscular dystrophy prevalent area and on the utilization of isolated fractions of the leaf seleno compounds in preruminating lambs. One week following application of75SeO32−to the leaf surfaces, 42% and 17% of the75Se activity was found to be present as selenocystine and selenomethionine, respectively, the majority of which was protein-bound. Approximately 11% of the applied selenium remained as75SeO32−. Five percent of75Se activity was attributable to three ninhydrin-negative materials of unknown composition isolated by 80% ethanol and water extractions. A trace of selenium was present bound to the leaf phospholipids. Data obtained from feeding various leaf preparations to lambs indicated that the water-soluble selenium compounds (chiefly selenite) and the seleno-amino acids contained in the ethanol and proteolytic enzyme extracts were effectively absorbed and retained. The similarity in75Se retention values for the latter extracts suggested that the uncharacterized materials in the ethanol fraction and the seleno-amino acids (enzyme digest) had comparable availabilities. The lipid-bound75Se was relatively poorly absorbed and retained. Regardless of the form of selenium ingested, the data indicated a similar distribution of the element between the tissues studied and a high proportion of activity associated with the tissue proteins.