Ruffed Grouse Tolerance and Biotransformation of the Plant Secondary Metabolite Coniferyl Benzoate

Ruffed Grouse (Bonasa umbellus) consumption of quaking aspen (Populus tremuloides) flower buds is determined, in part, by the concentration of coniferyl benzoate (CB) in the bud. Understanding the physiological effects of this compound may clarify whether the association between annual fluctuations in CB and Ruffed Grouse population levels has a cause/effect relationship. We determined the maximum level of dietary CB that Ruffed Grouse can tolerate by feeding captive grouse a formulated diet treated with eight concentrations of CB. Loss of body mass was used to indicate toxicity. Biotransformation products from CB were identified in order to determine the detoxication mechanisms em- ployed and the presence of potentially toxic CB metabolites. Ruffed Grouse will consume up to 2 g kgg' day-' of CB before rapid mass loss ensues. High dietary levels of CB were associated with decreased food intake and increased water excretion. Serum uric acid, as- partate aminotransferase, and alanine aminotransferase levels did not change significantly with increased levels of dietary CB. Mass loss that was associated with a CB intake of 2.3 g kg-' day-' could be explained by decreased food intake but could not be attributed to any specific toxic effect. It is uncertain whether the decreased food consumption that occurred at high CB intake levels was prompted by toxicity avoidance or decreased food palatability. Ruffed Grouse appear to use glucuronic acid, sulfate, and omithine conjugation, along with hydrolysis, reduction, and oxygenation reactions, when detoxifying CB. Nine biotransfor- mation products were identified, including ferulic acid and 4-vinylguaiacol. The latter com- pounds are known to interfere with reproduction in other animals.