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United States Department of Agriculture

Agricultural Research Service

Research Project: MANAGEMENT OF TEMPERATE PASTURES AND SILVOPASTURES FOR SMALL FARM LIVESTOCK PRODUCTION Title: The facts about sunn hemp toxicity

Authors
item Mosjidis, Jorge -
item Burke, Joan
item Hess, Joseph -

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 2011
Publication Date: June 11, 2012
Citation: Mosjidis, J.A., Burke, J.M., Hess, J.B. 2012. The facts about sunn hemp toxicity. Crop Science. 52:1469-1474.

Interpretive Summary: Recent interest in sunn hemp in the continental USA stems from the need to find summer cover crops that can be used as green manure. This species is ideal because of its fast growth, nitrogen fixation capacity and ability to reduce weed growth. It also has value as a livestock forage as it is high in protein; however, some publications indicate toxicity of sunn hemp seed and forage to livestock. Researchers at Auburn University and USDA, ARS in Booneville, Arkansas determined that statements on sunn hemp toxicity to livestock were unwarranted and may have been due to toxicity problems in other crotalaria species. In fact, sheep and goats thrived on grazing sunn hemp, which was a valuable summer forage. This information is important to crop and livestock producers, extension agents, and scientists.

Technical Abstract: Sunn hemp (Crotalaria juncea L.) is an annual plant widely grown in the tropics. The genus Crotalaria includes some species known to be toxic to animals. Development of seed producing cultivars for the continental USA at Auburn University, AL, has raised the question if its seed and forage are toxic. This review will present the evidence reported in the literature on the presence of toxic compounds in sunn hemp seed and foliage and other Crotalaria species found in the USA and their effect on animals. Results from research on sunn hemp demonstrate it is a valuable source of forage with not toxic effects. The seed does not cause acute toxicity to domestic animals because it has only a small amount of the toxic pyrrolizidine alkaloids characteristic of the genus Crotalaria. Thus, its presence as a feed contaminant does not pose a problem. However, sunn hemp seed should not be incorporated in animal diets because depending on the amount in the diet and the length of time that the diet is fed, it may cause weight loss and potential death. Conflicting reports regarding seed toxicity of C. juncea found in the literature appear to be caused by the amount of seed included in the diet, length of time the diet was fed and animal species that ate it. Statements indicating that sunn hemp forage is toxic seem to be due to misinterpretation of the literature and unwarranted extension of the toxicity problems found in other crotalarias to sunn hemp.

Last Modified: 10/25/2014
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