Toxicity testing of leaves from oak (Quercus robur) harvested in Aust-Agder county, Norway.

Abstract

Lethal toxic nephrosis was diagnosed in nine free-living moose (Alces alces) in AustAgder county, southern Norway, during the summers of 1995 and 1996 (VikOren et al., 1999). Most cases occurred during the second half of June, and it was concluded that the disease probably resulted from ingestion of nephrotoxic plants. According to results from summer browsing studies on moose in Aust-Agder, three diierent plants known to be nephrotoxic to domestic ruminants were being ingested (Danielson and Olsen, 1994; Damli and Roer, 1995; Bjerga, 1996). These are oak (Quercus spp., bog asphodel (Narthecium ossifragum) and ¢eld sorrel (Rumex acetosella) (Malone et al., 1992; Maxie, 1993; Flai Oyen et al., 1995a,b,c, 1997). However, R. acetosella toxicosis is associated with oxalate precipitation in the renal tubules (Maxie, 1993), a ¢nding that did not occur in the Agder material. VikOren and colleagues (1999) therefore suggested ingestion of oak or N. ossifragum as being the cause of the disease. Toxicity testing of N. ossifragum has been performed in several cervid species (Flai Oyen et al., 1999). Moose and red deer (Cervus elaphus) were found to be highly susceptible, reindeer (Rangifer tarandus) moderately susceptible, and fallow deer (Dama dama) refractory to the N. ossifragum nephrotoxin. To clarify whether oak was implicated in the aetiology of toxic nephrosis in moose in Aust-Agder, toxicity testing of oak harvested there at the time of main occurrence of the disease was desirable. A dosing experiment was attempted in two wild moose calves, captured when about 3 months old. During captivity, the calves seemed little stressed when left alone, and had a good appetite, browsing up to 50 g plant material Veterinary Research Communications, 23 (1999) 317^321 # 1999 Kluwer Academic Publishers. Printed in the Netherlands