Common Name
Alsike clover
Botanic Name
Trifolium hybridum (ITIS) Trifolium elegans Savi, Trifolium hybridum ssp. elegans (Savi) Asch. & Graebn., Trifolium hybridum var. elegans (Savi) Boiss.,Trifolium hybridum var. pratense Rabenh.)
Plant Family
Fields, pastures, roadsides and waste places. Alsike clover likes moist areas, and prefers high rain fall areas.
Widely distributed in the northern States
Animals Affected
Horses and occasionally cattle
Alsike clover - Trifolium hybridum
Toxic Principle
The toxin responsible for the liver disease and photosensitization (trifoliosis) has not been determined. A fungus growing in the clover may play a part in causing the disease. The photosensitization in conjunction with liver disease can be attributed to the accumulation of phylloerythrin in the horse's circulation.
Perennial herbs with taproots, giving rise to erect stems, 1-2 feet in height. Leaves are alternate, trifoliate, hairless; leaflets broadly eliptic with toothed margins. Flowers are white to pink, the banner longer than the wings and keel. The seeds are produced in a smooth, olive-green pod.
Remove all clover from the horses diet, keep the the horse indoors out of the sun, and gently clean affected skin with mild antiseptic solution until lesions heal.
Nervous System
In the acute form of alsike clover poisoning horses show signs of hepatic encephalopathy - aimless wandering, head pressing, yawning, progressing to recumbency and death
Integumentary System
Photosensitization. The white areas of the animal's skin become raised, reddened, painful and eventually dry and slough-off. The white areas on the legs and face are often the worst affected.
Hepatic System
In the second more common form of alsike clover poisoning, signs of liver disease predominate. Jaundice, weight loss, neurological disturbances such as head-pressing, circling and secondary photosensitization. Histologically, biliary hyperplasia perilobular fibrosis in chronic cases may be seen.
Diagnostic Tests
Liver biopsy may show biliary hyperplasia and fibrosis of the portal triads
The presence of photosensitization, liver disease and alsike clover in the horses diet are highly suggestive. Elevated serum liver enzymes and a liver biopsy are helpful in confirming Alsike clover poisoning.
Special Notes
Alsike clover should not be included in grass seed mixes intended for horse pastures. There are fungal diseases affecting clover that will also cause liver disease in horses grazing the infected plants. One such clover diseases is 'Sooty clover disease' caused by the fungus Cymodothia trifolii.The fungus causes black spotting on the underside of the leaves and is most prevalent in high rainfall areas or irrigated pastures. References: 1. Nation PN. Hepatic disease in Alberta horses: A retrospective study of 'alsike clover poisoning'.1973-1988. Can Vet J. 1991, 32: 602 - 607. 2. Nation PN. Alsike clover poisoning: A review Can Vet J. 1989, 30:410-414. 3. Traub JL, Potter KA, Bayley WM, et al: Alsike clover poisoning. Mod Vet Prac 63: 307-309 1982.
Secondary photosensitive from clover pasture