CONDITIONED FLAVOR AVERSIONS IN SHEEP - THE RELATIONSHIP BETWEEN THE DOSE-RATE OF A SECONDARY PLANT-COMPOUND AND THE ACQUISITION AND PERSISTENCE OF AVERSIONS

Within the overall objective of whether ruminants are able to form con ditioned aversions (CFA) toward a food flavour associated with the adm inistration of an aversive stimulus which occurs naturally in food pla nts (oxalic acid, OA), two specific objectives were tested: (1) whethe r the rate and degree of formation of CFA are dependent on the dose ra te of OA administered and (2) whether the persistence of formed CFA de pends on the previous dose rate of OA. Sheep were conditioned to assoc iate the specific flavour of one of two novel foods with either the or al administration of OA or equivalent placebos. Four dose rates of OA were tested (0.06, 0.12, 0.18 and 0.24 g/kg sheep live weight per d), with twelve sheep per dose. Each conditioning period lasted for 8 d an d was repeated four times. At the end of each conditioning period the preference for the two flavours was measured in short-term, 20 min pre ference tests. The persistence of the CFA was measured at 0, 7, 21 and 49 d after the completion of the conditioning phase with long-term, 3 h preference tests. The results of the experiment indicated that: (1) the rate and degree of formation of CFA were dependent on the rate of administration of OA; (2) sheep required repeated exposures to the lo wer dose rates of OA in order to develop CFA and these CFA did not per sist in the absence of continual reinforcement; (3) CFA to the higher dose rates of OA were developed after as little as one exposure and pe rsisted over a period of at least 7 weeks. These findings are consiste nt with the expectation that ruminants should be able to select a diet which minimizes the risk of consumption of potentially harmful foods, whilst at the same time maintaining a degree of flexibility in their feeding behaviour.