Persistence of aversions to larkspur in naive and native cattle.

Abstract

The objective of this study was to create and maintain a long lasting aversion to tall larkspur (Delphinium barbeyi Huth) under field grazing conditions. Two grazing trials were conducted: the first used cattle naive to larkspur, and the second used cattle that were familiar with larkspur. In the first trial, 12 mature cows that were not familiar with larkspur were randomly allocated to Averted and Control groups (n = 6). They were fed larkspur (a novel food) and the Averted group was dosed with lithium chloride (200 mg/kg body weight) to create the aversion. Both groups were then taken to larkspur-infested mountain rangeland where they grazed in 2 separate pastures during the late summer of 1993, 1993, 1994, and 1995. The aversion was not reinforced in 1994 or 1995. Diets were quantified by bite count. The Averted group abstained from eating larkspur for 3 years. The Control group grazed larkspur for an average of 14% of bites. Three Control cows died from larkspur poisoning in 1993, and another cow was poisoned, but survived in 1994. During the last 2 weeks of the 1995 trial, the Averted and Control groups were placed together, and the social influence of the Control cows eating larkspur caused the Averted cows to sample larkspur and gradually extinguished the aversion. In the second trial (1994 and 1995), 5 native cows that had grazed on the allotment and were familiar with larkspur were averted to larkspur by the procedure described above. They abstained from eating larkspur while grazing separately, but extinguished the aversion when placed with non-averted Control cows at the end of the study in 1995. Aversions are retained in long term memory and may last indefinitely if averted cattle graze separately.