Alsike clover (Trifolium hybridum
) is a short-lived, non-creeping perennial that is often used for hay, pasture, and soil improvement. T. hybridum
grows well in northern latitudes and at high elevations. It is most frequently found in the northeastern United States and Canada. T. hybridum
has smooth green leaves with a tapering point. It has a semi-erect, sparsely branched, grooved stem and is hairy in its upper regions. The flowers are white or pale pink which turn brown at maturity.
If consumed, T. hybridum
can cause acute and/or chronic poisoning in horses. Chronic poisoning (known as 'Big liver syndrome') is an irreversible liver disease often accompanied by neurological symptoms. Acute poisoning occurs in the form of photosensitivity
. There is also a potential for nitrate poisoning
The majority of T. hybridum
poisoning cases occur between April and November. Horses consuming as little as 20% of fresh pasture or hay containing T. hybridum
can begin to show signs of liver failure. T. hybridum
poisoning does not appear to occur every time it is consumed. It is thought that the toxicity may be caused by a mycotoxin which is either created by a fungus growing on the plant, or created/accumulated by the plant under stressful growing conditions.