U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version

October 2004


Published by Elsevier B.V.


Multiple experiments were conducted with a mammalian herbivore to determine how experience

with plant secondary metabolites (terpenes and tannins) influenced acquisition of new aversions to

diets containing these same plant metabolites. Goats (Capra aegagrus hircus) were employed as

behavioral models for this study. Twenty-four subjects were assigned to three treatment groups that

received 20 days of experience with test diets: (A) terpene diet only; (B) tannin diet only; and (C)

terpene and tannin diets offered singly on alternate days. In experiment 1, all subjects were offered

both diets in a two-choice test to determine if experience affected diet preference. Both treatments A

and B demonstrated significant preferences for the terpene diet, while treatment C subjects did not

exhibit a diet preference.

Both diets were offered to all subjects and immediately followed with a 150 mg/kg dose of lithium

chloride (LiCl) in experiment 2. A two-choice preference test was conducted to determine if lithiuminduced

toxicosis would be associated with the least familiar diet. As in experiment 1, treatments A

and B preferred terpene diet while treatment C did not demonstrate a preference. Lithium chloride

exposure was specifically paired with one of the test diets in experiment 3. A two-choice preference

test demonstrated that treatments A, B, and C acquired aversions to tannin diet when it was paired

with LiCl administration. However, terpene-paired LiCl administration did not produce an aversion

to the terpene diet in treatments A and B. Treatment C preferred tannin diet when the terpene diet was

paired with LiCl.

A novel flavor was added to the choice of diets in experiment 4. All subjects were offered citric

acid (CA), terpene, and tannin-containing diets and immediately dosed with LiCl. Subjects that

acquired aversions to the tannin diet in experiment 3 continued to avoid tannin diet in experiment 4

and preferred terpene diet while eating significant quantities of the novel CA diet. Only treatment C

subjects with previous terpene-paired LiCl exposures demonstrated aversions to the CA diet. These

results have implications for the conduct of flavor aversion studies and the application of flavor

aversion learning (FAL).