Submitted to: Book Chapter
Publication Type: Book / chapter
Publication Acceptance Date: 12/15/2005
Publication Date: 10/20/2007
Citation: Dunson, W.T., Scott, C.B., Campbell, E.S., Taylor, C.A., Carr, M.A., Callaway, T.R. 2007. Rumen function and the ability of goats to consume redberry juniper (Juniperus pinchottii). In: Panter, K.E., Wierenga, T.L., Pfister, J.A., editors. Poisonous Plants - Global Research and Solutions. Logan, Utah: Wiley Press. p. 377-385. Interpretive Summary: Redberry juniper is an invasive conifer that is expanding its current range and is costly to eradicate. Animals do not consume large amounts of juniper because it contains toxic compounds that cause an aversion in animals. However, goats can be conditioned to consume large amounts of juniper. This has led to the use of goats as a biocontrol strategy to clear land of juniper. However the underlying ability of goats to consume large amounts of this toxic plant is unclear. The rumen microbial (bacterial) population of the goat digestive system allows some plant toxins to be detoxified. Therefore, this study was undertaken to determine if the ability of goats to consume redberry juniper was due to changes in the ruminal microbial population. Results suggest that rumen microbial adaptation is not responsible for the ability to increase intake of juniper.
Technical Abstract: Some goats are able to increase intake of redberry juniper (Juniperus pinchotii) through exposure early in life even though the plant contains terpenoids that limit intake. Toxin adaptation typically results from changes in rumen microbial populations leading to toxin degradation or through toxin metabolism/degradation in the liver. The purpose of this study was to determine if changes in rumen microbial populations enabled goats to increase intake of redberry juniper. In Experiment 1, 26 Boer-Spanish cross goats were placed in individual pens and fed alfalfa at 2% BW for 14 days. Thirteen of the 26 goats were randomly chosen and also fed fresh redberry juniper for 2 hrs each day. Three of the 13 goats in each group were ruminally-cannulated to facilitate collection of rumen fluid. Initially, goats were fed 50 g/day. If goats consumed all of the juniper, additional juniper was fed the following day. Intake and serum metabolite levels were monitored to assess toxicosis. Rumen fluid was collected from 3 rumen cannulated goats fed juniper and 3 rumen cannulated goats fed alfalfa to assess in vitro terpene degradation, volatile fatty acid (VFA) profiles, and ammonia levels. In Experiment 2, 10 goats unfamiliar with juniper were inoculated with rumen fluid either from goats fed juniper or goats fed alfalfa alone. Juniper intake was monitored for 10 days thereafter. In both experiments, juniper intake increased daily throughout the trial. During Experiment 1, serum metabolite levels were elevated in goats consuming juniper, but none were outside the normal range for healthy goats. In vitro terpene degradation was similar for both goats fed juniper or alfalfa alone. Ammonia levels were similar for goats fed juniper or alfalfa alone. Some VFA levels differed among treatments. Variations in VFA levels between treatments were probably the result of microbial death when terpenes were added to rumen fluid. In Experiment 2, juniper intake was similar irrespective of the source of rumen fluid. Results of these experiments suggest rumen microbial adaptation does not appear to be responsible for a goat's ability to increase intake of juniper.