Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 13, 2005
Publication Date: August 15, 2005
Citation: Estell, R.E., Fredrickson, E.L. Anderson, D.M. Remmenga, M.D. 2005. Effects of gamma-terpinene, terpinene, alpha-copaene, and alpha-terpinene on consumption of alfalfa pellets by sheep. Journal of Animal Science. 83:1967-1971. Interpretive Summary: A major concern of producers and land managers is encroachment of shrubs into arid grasslands. These shrubs are often unpalatable to livestock and wildlife because of secondary chemicals. We are studying the role of these plant chemicals in shrub consumption by herbivores. Our early work showed that livestock preference for tarbush varied greatly from plant to plant and that chemicals on the leaf surface were partly responsible for the variability. We applied volatile chemicals in tarbush to alfalfa pellets and fed to lambs to determine if these terpenes regulate intake when applied individually. None of the four compounds tested (gamma-terpinene, terpinolene, alpha-copaene, or alpha-terpinene) reduced intake in this study. These four compounds do not appear to be involved in the avoidance of shrubs by livestock. Learning which compounds control intake will ultimately help us find ways to alter the amount of a particular plant species eaten by livestock.
Technical Abstract: Although plant secondary chemistry influences shrub consumption by free-ranging ruminants, the effects of many specific compounds on herbivory have not been examined. We conducted four experiments to examine effects of individual terpenes on alfalfa pellet intake by lambs. Forty-five lambs (9 lambs/treatment) were individually fed alfalfa pellets sprayed with either gamma-terpinene, terpinolene, alpha-copaene, or alpha-terpinene at one of five concentrations in an ethanol carrier. Treatments (0, 0.5, 1, 2, and 10X) were multiples of the concentration (X) of a specific terpene on the leaf surface of Flourensia cernua. Terpenes were applied to alfalfa pellets (0.64 kg.lamb-1.d-1, DM basis), and consumption was measured during a 20-min interval for 5 d. A day effect (P < 0.02) was detected for gamma-terpinene on intake (P < 0.0001 for both linear and quadratic contrasts). A treatment effect (P < 0.02) was observed for alpha-copaene with intake on the 2X treatment lower than other treatments. No effect of terpinolene or alpha-terpinene on intake was detected in this study. None of the chemicals tested were strongly related to intake of alfalfa pellets by lambs under the conditions of this study.