Herbivores ingest large quantities of plant secondary metabolites (PSMs) due to their abundance in plants. While the PSMs woody plants produce can act as defenses against mammalian herbivory, herbivores have behavioural and physiological means for coping with PSMs. Understanding the relationship between physiology and behavior in mitigating toxicity from PSMs is a critical step toward enhancing productivity of savannas. We hypothesized that the monoterpene camphor influences food intake in sheep, and that rate of elimination of camphor from the body influences food intake. We used monoterpenes as an example of herbivore response to PSM. We infused one group of lambs intravenously with 40 mg/kg BW camphor dissolved in methanol and intralipid. We dosed another group of lambs intraruminally with a single-bolus dose of 125 mg/kg BW camphor dissolved in vegetable oil. We monitored feeding behavior. During intravenous infusions, dosed lambs stopped feeding sooner than control lambs (P < 0.05). Lambs began feeding again soon after the infusions stopped, which was consistent with the rapid rates at which camphor was eliminated from the body. Ruminally dosed lambs stopped feeding sooner than control lambs (P < 0.05). We conclude that systemic concentrations and rates of elimination influenced feeding behaviour. Thus, lambs expressed physiological and behavioural responses that enabled them to cope better with the potentially toxic effects of camphor. We draw inferences from this example based on known characteristics of chemically defended plants and generalize to chemically defended plants in wooded rangelands.
Responses of Lambs to Camphor HighlightOpportunities for Management of SavannasOptions Méditerranéennes Series A
Citation InformationDziba LE, Provenza FD, and Hall JO. Responses of Lambs to Camphor Highlight Opportunities for Management of Savannas. Options Méditerranéennes Series A. 85: 191-196, 2010.