Details

Common Name
Yellow sweet clover
Botanic Name
Melilotus officinalis, M. Alba (White sweet clover)
Plant Family
Fabaceae
Habitat
A drought tolerant virtual weed of roadsides, fields, waste areas
Animals Affected
Catttle, horses. Sheep are quite resistant.
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Toxic Principle
A variety of different fungi including Penicillium and Aspergillus spp. growing on sweet clover are capable of converting coumarin to dicoumarol, the principle toxin. Dicoumarol interferes with prothrombin and other vitamin K dependent coagulation factors VII,IX,X. Signs of poisoning may not appear for up to 3 weeks after feeding moldy sweet clover hay, and depends on the quantity of dicoumarol consumed. Poisoning occurs when dicoumarol levels exceed 10 mg/kg of hay. Hay containing dicoumarol levels of 10-20 mg/kg of feed can be fed for 100 days before poisoning develops. Feeds containing 60-70 mg/kg of feed can cause poisoning in as little as 21 days.
Description
As biennials, both species grow to 5 ft (1.5 m) high and have compound leaves with 3 leaflets that have serrated edges, with the terminal leaflet on a stalk. The leguminous flowers are produced in axillary racemes up to 5 inches in length. The flowers are yellow or white, depending on the species. Smooth yellow seeds are produced in pods 2-3 mm long.
Gastrointestinal
Black tarry feces (melena)
Musculoskeletal
Weakness and lameness due to hemorrhaging into joints and muscles. Large swellings develop(hematomas) especially over protruberent body areas.
Treatment
Whole blood transfusions as necessary. 1 mg/lb body wt of vitamin K1 should be injected to restore prothrombin time to normal within 24 hours. However the cost may be prohibitive and vitamin K3(menadione sodium bisulfite) although less effective, may be administered. If vitamin K3 is given parenterally, the dosage should be 1 mg/kg body wt. and should not exceed 2 mg/kg body weight. Higher doses of vitamin K3 administered parenterally greatly increases the risk of vitamin K renal toxicosis especially in horses.
Cardiovascular system
Severe hemorrhaging will cause anemia (pale mucous membranes, rapid heart rate)and death.
Respiratory System
Hemorrhaging from the nose (epistaxis)
Renal System
Hematuria
Reproductive System
Excessive hemorrhaging during calving.
Ocular System
Hemorrhaging into the anterior chamber of the eye.
Diagnosis
Hemorrhaging due to failure of clotting mechanism. Prothrombin times above 40 seconds are suggestive of decreased clotting ability. Blood prothrombin, activated partial thromboplastin times, and clotting times are markedly increased from their normals of 9 to 12 sec, 30 to 45 sec, and 3 to 15 min, respectively.
Special Notes
Signs of poisoning may not appear for up to 3 weeks after feeding moldy sweet clover hay, and depends on the quantity of dicoumarol consumed. Poisoning is likely to occur when dicoumarol levels exceed 10 mg/kg of hay. Hay containing dicoumarol levels of 10-20 mg/kg of feed can be fed for 100 days before poisoning develops. Feeds containing 60-70 mg/kg of feed can cause poisoning in as little as 21 days. Prothrombin times above 40 seconds are suggestive of decreased clotting ability. Blood prothrombin, activated partial thromboplastin times, and clotting times are markedly increased from their normals of 9 to 12 sec, 30 to 45 sec, and 3 to 15 min, respectively. There are varieties of sweet clover that contain very low levels of coumarin and, therefore, hay from these varieties is safe, even if moldy. To prevent the risk of moldy sweet clover poisoning, sweet clover hay or haylage should not be fed for at least 3 weeks before parturition or elective surgery.
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