Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2014
Publication Date: 7/30/2014
Publication URL: http://handle.nal.usda.gov/10113/59648
Citation: Welch, K.D., Green, B.T., Panter, K.E., Gardner, D.R., Pfister, J.A., Cook, D. 2014. If one plant toxin is harmful to livestock, what about two? Journal of Agricultural and Food Chemistry. 62(30):7363-7369.
Interpretive Summary: Animals are exposed to numerous potentially toxic compounds every day. This may occur as the result of exposure to multiple toxins simultaneously via the same route, or as a cumulative exposure to multiple toxins encountered over time from multiple exposure routes. In most cases where livestock are poisoned by plants in a range setting, there is more than one potential poisonous plant in that area. Additionally, many poisonous plants contain more than one toxin. Often times, much is known regarding the toxicity of the individual plants and their toxins, however, little is known regarding the effect of co-exposure to multiple toxic plants or even multiple toxins from an individual plant. In this review, we present results from experiments in which we investigated the role of two different types of alkaloids from larkspur plants on the overall toxicity of the larkspur plant. We also present results from experiments characterizing the effect of co-exposure to two different plants, each containing different classes of toxins. These experiments provide examples of the mixture effects that result from exposure to multiple toxins, either from an individual plant or from two different plants. The tall larkspur experiments demonstrate that MDL-type alkaloids exacerbate the overall toxicity of the MSAL-type alkaloids and should be accounted for when predicting potential toxicity of larkspur populations. The results from the death camas and low larkspur experiments demonstrate that there is an additive effect of dosing mice with a combination of MLA and zygacine. However, there is no enhanced toxicity in sheep dosed with larkspur and death camas due to their resistance to larkspur. This information will be useful in further developing livestock management recommendations for ranchers and in designing additional experiments to study the toxicity of multiple plant toxins livestock species.
Technical Abstract: When livestock are poisoned by plants in a range setting, there is normally more than one poisonous plant in that area. Additionally, many plants contain more than one compound that is toxic to livestock. Often times, much is known regarding the toxicity of the individual plants and their individual toxins, however, little is known regarding the effect of co-exposure to multiple toxic plants or even the effect of multiple toxins from an individual plant. In this review, we discuss some basic principles of mixture toxicology with a focus on our recent research wherein we examined the effect of co-administering multiple plant toxins from the same plant and the effect of co-administration of two different poisonous plants, each with different types of toxins. As combined intoxications are likely common, this information will be useful in further developing management recommendations for ranchers, and in designing additional experiments to study the toxicity of multiple poisonous plants to livestock.