Submitted to: Small Ruminant Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2004
Publication Date: 4/1/2005
Citation: Estell, R.E., Fredrickson, E.L., Anderson, D.M., Havstad, K.M., Remmenga, M.D. 2005. Effect of previous exposure to sheep to monoterpene odors on intake of alfalfa pellets treated with camphor or alpha-pinene. Small Ruminant Research. 58:33-38. Interpretive Summary: Loss of grasslands to invasive shrub species is a global concern to livestock producers. Shrubs often contain chemicals that cause them to be unpalatable to livestock. Our research examines the role of plant chemicals in regulating intake of shrubs by ruminants. Our work has shown that preference of livestock for tarbush differed from plant to plant, partly because of differences in the chemicals present on the leaf surface. In previous studies, both camphor and alpha-pinene decreased intake when applied to alfalfa pellets. In this study, we attempted to expose lambs to the aroma of these two volatile compounds during feeding in an attempt to desensitize them to the repellent effects. However, feeding lambs for eight weeks while being exposed to the smell of these monoterpenes had no effect on intake of feed treated with the compounds during weeks 9 and 10. The purpose of these studies is to understand how plant chemicals control intake and to find methods to alter which plants are eaten.
Technical Abstract: Lambs were subjected to odors of two monoterpenes (camphor and alpha-pinene) that decreased intake in a previous study to determine if exposure during feeding modified their effects on subsequent intake. Two experiments were conducted using a split-plot design and with 36 ewe lambs (mean BW = 23.1 and 42.2 kg in Exp. 1 and 2, respectively) group-fed alfalfa pellets (3.8% of BW, DM basis) in enclosed portable buildings for 2 h each morning for 56 d. Nine lambs were randomly assigned to each of four buildings, and 25 g of camphor (Exp. 1) or 50 ml of alpha-pinene (Exp. 2) were placed in a mesh-covered container in the center of the feeder in two buildings immediately before feeding. After the 8-wk exposure period (phase 1), lambs were individually fed alfalfa pellets (640 g, DM basis) for 20 min each morning for 10 d (5-d adaptation, 5-d collection) in a metabolism building (phase 2). Treatments were sprayed on alfalfa pellets at levels representing the concentration of that chemical in Flourensia cernua or at 10-fold that concentration. Controls received the ethanol carrier only. During phase 2, lambs were fed in three groups (n = 12), stratified such that one lamb from each building received each treatment in each group. Lambs were housed as one group and fed alfalfa pellets at 4.7% of BW (DM basis) except during the 20-min tests. No interactions with day were detected for intake during adaptation or collection periods for either chemical (P > 0.05); therefore, data were pooled across day. Exposure to the volatile aroma for 8 wk had no effect on intake during the subsequent 10-d interval for either monoterpene (P > 0.05). Moreover, intake during the collection period was not affected by treatment concentration (P > 0.05). Neither concentration of the terpene applied to alfalfa pellets nor previous exposure to the volatile aroma from camphor or alpha-pinene altered feed intake under the conditions of this study.