CONIFERYL BENZOATE IN QUAKING ASPEN (POPULUS-TREMULOIDES) - ITS EFFECT ON ENERGY AND NITROGEN DIGESTION AND RETENTION IN RUFFED GROUSE (BONASA-UMBELLUS)

Many plant secondary metabolites have been identified as feeding deter rents; however, the physiological effects of these compounds remain la rgely unknown. Coniferyl benzoate (CB) is the principal secondary meta bolite in quaking aspen (Populus tremuloides) flower buds, a primary w inter food for ruffed grouse (Bonasa umbellus), and is a feeding deter rent for grouse and other birds. We conducted mass-balance trials with captive ruffed grouse to determine the effect of this compound on die tary mass and energy assimilation. A method is described for correctin g assimilation coefficients for the intake of dietary plant secondary metabolites whereby changes in a bird's ability to utilize dietary mas s and energy can be distinguished from artifacts due to energy and mas s dilution by plant secondary metabolites. Nitrogenous excretory produ cts were measured to determine nitrogen balance and sources of nitroge n loss. In addition, energy losses resulting from the excretion of CB detoxification products were quantified. Birds that fed on a high CB d iet were in negative nitrogen balance and excreted higher amounts of o rnithine and ammonium than birds on control diets. Excretion rates for ornithine and ammonium may be even higher for birds feeding on aspen buds because other phenolic compounds must be detoxified along with CB . Coniferyl benzoate did not decrease the ability of ruffed grouse to utilize dietary energy but did decrease utilization efficiencies simpl y by a dilution effect. overall, assimilation efficiencies increased o ver the 3-mo study. Acidosis, from acidic detoxication products, and n itrogen loss may be two reasons why wild ruffed grouse avoid feeding o n aspen buds containing high CB levels; however, the principal mechani sm by which CB acts as a feeding deterrent is still uncertain.