Induction of conditioned taste aversion in goats

Abstract

The possibility of inducing conditioned taste aversion (CTA) by injection of apomorphine in 24 young Maltese goats and the effect of social models on the feeding behaviour of conditioned animals were evaluated. The experimental feeds were oats seed (OS) and rabbit alfalfa pellets (RP). Animals were divided into six social groups (S), including conditioned and unconditioned subjects, and two non-social groups (NS), with conditioned animals only. Within the S groups each conditioned animal stood between two unconditioned subjects while eating. When feeds were paired with apomorphine (APO feeds), no significant differences were found in consumptions between conditioned animals of the S and NS groups ( P > 0.05). Unconditioned animals of the S groups did not modify their feed intakes and were not able to stimulate the intake of the APO feeds in the conditioned subjects. Consumption of the APO feeds was significantly lower than that of the control feeds ( P < 0.001). RP was always consumed more than OS, even when it was associated with apomorphine, probably because of its physical similarity to the pellet of the base diet. In the two-choice test 16 out of 24 goats chose the control feed first and eight the feed associated with illness. When they chose the latter, it was RP seven out of eight times and OS only once ( P < 0.01). The amounts of the consumed control feeds were significantly higher than those of the APO feeds ( P < 0.01). The significant reduction in consumption of the APO feeds in comparison with the control feeds showed that goats can learn to avoid a feed that immediately produces illness. The conditioned animals did not modify their feed intakes following the influence of the unconditioned subjects.