Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2000
Publication Date: 6/1/2000
Citation: ESTELL, R.E., FREDRICKSON, E.L., ANDERSON, D.M., HAVSTAD, K.M., REMMENGA, M.D. EFFECT OF INDIVIDUAL TERPENES ON CONSUMPTION OF ALFALFA PELLETS BY SHEEP. JOURNAL OF ANIMAL SCIENCE. 2000. V. 78. P. 1636-1640. Interpretive Summary: Grasslands in arid regions throughout the world are becoming shrub infested. Most shrub species growing in the Chihuahuan Desert contain noxious chemicals and are not eaten by livestock. We are studying the role of one group of plant chemicals (terpenes) in controlling shrub consumption by cattle and sheep. In a previous study, we found that in one shrub species (tarbush), the amount of leaves eaten by livestock varied greatly among plants. Some of the variation appeared to be related to the amount of specific terpenes on the leaf surface. The present study was part of a series of studies to determine which specific compounds regulate intake. Chemicals were individually sprayed on alfalfa pellets to determine if they affected consumption of feed by sheep. We measured the effect of five compounds (p-cymene, alpha-humulene, 1,8-cineole, 3-carene, or sabinene) on intake. None of the compounds examined in these five experiments altered feed consumption. The systematic identification of specific plant chemical that are responsible for the avoidance of shrubs by livestock will help us understand the physiological control mechanisms of diet selection and may help us to find ways to alter the amount of a particular plant species eaten by livestock.
Technical Abstract: We examined effects of five individual terpenes on alfalfa pellet intake of lambs. In each experiment, 45 lambs were individually fed alfalfa pellets sprayed with either p-cymene, alpha-humulene, 1,8-cineole, 3-carene, or sabinene at one of five concentrations. Treatment levels (0, .5, 1, 2, and 10X) were multiples of the concentrations (X) of specific terpenes in tarbush that were related to differential herbivory by livestock in previous studies. Treatments were applied to alfalfa pellets (.64 kg/lamb/d, DM basis), and consumption during a 20-min interval was measured for 5 d. Lambs were adapted to handling and pen feeding for 10 d, and were maintained and fed alfalfa pellets in one group (except during 20-min tests) at a mean total daily intake of 4.7% of BW (DM basis). None of the five compounds examined decreased pellet consumption during the 20-min interval. These five mono- and sesquiterpenes do not appear to be responsible for differential herbivory of individual tarbush plants by livestock.