Original Research

Annual ryegrass toxicity in Thoroughbred horses in Ceres in the Western Cape Province, South Africa

J.D. Grewar, J.G. Allen, A.J. Guthrie
Journal of the South African Veterinary Association | Vol 80, No 4 | a211 | DOI: https://doi.org/10.4102/jsava.v80i4.211 | © 2009 J.D. Grewar, J.G. Allen, A.J. Guthrie | This work is licensed under CC Attribution 4.0
Submitted: 25 May 2009 | Published: 28 May 2009

About the author(s)

J.D. Grewar,
J.G. Allen,
A.J. Guthrie,

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An outbreak of annual ryegrass toxicity occurred on a Thoroughbred stud in Ceres in the Western Cape Province of South Africa. This is the 1st report of annual ryegrass toxicity in horses in South Africa, although the condition has been reported in cattle and sheep populations in the past. Annual ryegrass toxicity is characterised by a variety of neurological signs including tremors, convulsions, recumbency and in many cases death. The description of the outbreak includes the history, clinical presentation and treatment protocol administered during the outbreak. Various epidemiological variables and their influence in the outbreak are also considered.


Annual Ryegrass Toxicity; Horse; Corynetoxins; Neurological; Magnesium Sulphate


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