Submitted to: Journal of Range Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 27, 2000
Publication Date: July 1, 2001
Citation: PFISTER, J.A., PANTER, K.E., GARDNER, D.R., STEGELMEIER, B.L., RALPHS, M.H., MOLYNEUX, R.J., LEE, S.T. ALKALOIDS AS ANTI-QUALITY FACTORS IN PLANTS ON WESTERN U.S. RANGELANDS. JOURNAL OF RANGE MANAGEMENT. 2001. Interpretive Summary: Alkaloids are a structurally-diverse group of chemical compounds with widely varying biological activities in animals and humans. Range plants that contain alkaloids poison more livestock worldwide than any other class of toxic compounds. Alkaloids usually have pronounced physiological reactions when ingested by livestock, and effects on animal health are often dose-dependent. Our objective in this review is to provide an overview of the effects of alkaloid-containing plants on livestock production on western rangelands and review management solutions. Losses to these plants can be reduced or eliminated by recognizing the toxic plant responsible on specific ranges, understanding when livestock graze the plant and how the toxin affects animals, altering management schemes or animal species to reduce the risk of losses, or using herbicidal control. Management of each toxic plant species is based on knowledge of the temporal and spatial dynamics of alkaloid concentration and consumption by livestock. Losses may be reduced by ensuring that livestock are not exposed or have reduced exposure either during periods of greatest risk (e.g., highest toxin concentrations), or when they are most likely to eat the plant in amounts sufficient to cause toxicity.
Technical Abstract: Alkaloids constitute the largest class of plant secondary compounds, occurring in 20 to 30% of perennial herbaceous species in North America. We review 7 major categories of toxic alkaloids, including pyrrolizidine (e.g., Senecio), quinolizidine (e.g., Lupinus), indolizidine (e.g., Astragalus), diterpenoid (e.g., Delphinium), piperidine (e.g., Conium), pyridine (e.g., Nicotiana), and steroidal (Veratrum-type) alkaloids. Clinically, effects on animal production vary from minimal feed refusal to abortion, birth defects, wasting diseases, agalactia, and death. There are marked species differences in reactions to alkaloids. This has been attributed to rumen metabolism, alkaloid absorption, metabolism, excretion or directly related to their affinity to target tissues such as binding at receptor sites. In spite of alkaloids reputed bitter taste to livestock, some alkaloid-containing plant genera (e.g., Delphinium, Veratrum, Astragalus, Oxytropis, and Lupinus) are often readily ingested by livestock. Management schemes to prevent losses are usually based on recognizing the particular toxic plant, knowing the mechanism of toxicity, and understanding the temporal dynamics of plant alkaloid concentration and consumption by livestock. Once these aforementioned aspects are understood, losses may be reduced by maintaining optimal forage conditions, adjusting grazing pressure and timing of grazing, aversive conditioning, strategic supplementation, changing livestock species, and herbicidal control.