Effects of gamma-terpinene, terpinolene, alpha-copaene, and alpha-terpinene on consumption of alfalfa pellets by sheep.

Although plant secondary chemistry influences shrub consumption by free-ranging ruminants, the effects of many specific compounds on herbivores have not been examined. We conducted four experiments to examine effects of individual terpenes on alfalfa pellet intake by lambs. Forty-five lambs were individually fed alfalfa pellets sprayed with 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 (a low-preference shrub for domestic ruminants). 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 was detected for gamma-terpinene on intake (P < 0.001 for both linear and quadratic contrasts). No effect of terpinolene, alpha-copaene, or alpha-terpinene on intake was detected in this study. None of the terpenes tested was strongly related to intake of alfalfa pellets by lambs under the conditions of this study.