Effect of Saponins on Palatability of Alfalfa to Meadow Voles1

Authors:
  • WKW. A. Kendall
    W. A. Kendall
  • KLK. T. Leath
    K. T. Leath
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Abstract
Forage constituents that effect the plant palatability are one of many factors that control animal intake. Saponins are biologically active compounds that occur in alfalfa (Medicago sativa L.) in various concentrations and may affect palatability. The purpose of this research was to evaluate the role of saponins in palatability. The meadow vole (Microtus pennsylvanicus) was used to test palatability because its small size and ready acceptance of forage permitted the assay of small amounts of forge and extracted saponins.Meals from alfalfas selected for high‐ or low‐saponin content with the Trichoderma viride Pers. ex Fr. or hemolysis bioassays were compared for palatability using meadow voles. The voles were fed a commercial mouse food ad libitum and offered a choice of the commercial food or test diet for 30 min at 0800 and 1600 daily. Saponin activity of the meals was evaluated with the T. viride bioassay. Purified saponin mixtures from ‘DuPuits’ and ‘Lahontan’ alfalfa and quinine sulphate were evaluated at various concentrations for palatability to voles.Meals of low‐saponin lines of alfalfa were generally more palatable than their corresponding high‐saponin lines except for selections of Lahontan which were both very palatable. The growth of T. viride was greatest on substrates with extracts of alfalfa meals that were most palatable to meadow voles. Purified saponins from Lahontan and DuPuits alfalfa reduced intake at a concentration of 4% of the diet. The palatability of 3% saponin from DuPuits in the diet was not increased by mixing with sucrose. Intake of quinine sulphate was inversely related to concentration, indicating that voles perceived the bitter substance.