• aversions;
  • bitter receptors;
  • meal size;
  • plant secondary compounds;
  • regulation


  • 1
    Many mammalian herbivores continually face the possibility of being poisoned by the natural toxins in the plants they consume. A recent key discovery in this area is that mammalian herbivores are capable of regulating the dose of plant secondary compounds (PSCs) ingested.
  • 2
    The ‘regulation model’ describes the factors driving ingestion of PSCs by mammals and can be dissected into two separate hypotheses related to meal size and inter-meal interval (IMI). Testing these hypotheses independently yields a more thorough understanding of the underlying and potentially interconnected mechanisms.
  • 3
    Three mechanisms could influence the size of meals that contain PSCs. These are the plasma concentration of PSCs, conditioned learning, and activation of bitter receptors in the intestine.
  • 4
    Two mechanisms are proposed to govern the IMI. The first predicts that IMI is dependent on the concentration of PSC metabolites in the plasma; feeding will not resume until metabolite concentrations are acceptable for further ingestion of PSCs. The second hypothesis proposes that the intestinal bitter receptors modulate IMI through release of satiety compounds.