Pasture Hazards
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Pasture Hazards Grazing Horses and Toxins: Issues Relatively small stomach, few bacteria Common names of plants vary and may confuse people If poisoning is suspected, call the vet first, then Animal Poison Control. Take horse to quiet place, blanket if needed Grab a sample of suspected toxic plant or photograph it Keep other livestock feeds away from horses Red Maple - Acer rubrum Unknown toxic principle in wilted leaves. Methemoglobinemia and intravascular hemolysis, weakness, polypnea, tachycardia, depression, icterus, cyanosis, brownish discolouration of blood and urine Black Locust Flattened, brown pods containing 4-8 seeds persist throughout winter Diarrhea, anorexia, weakness, posterior paralysis, depression, mydriasis, cold extremities, frequently laminitis and weak pulse Death infrequent, but recovery period is extensive Black Walnut Juglone, phenolic derivative of naphthoquinone Shavings with <20% black walnut toxic within 24 hours of exposure Depression, increased temperature, pulse, respiration rate, abdominal sounds, limb edema, lameness, severe laminitis Locoweed Two different genera of legumes most commonly found in the midwestern United States Twenty-four species of Oxytropis contain the neurotoxin swainsonine Erratic behaviour, aggression, lethargy, depression, loss of balance, nervousness, and abortion Symptoms reduce with time after exposure to locoweed, some nerve damage is permanent In horses, brain damage can make them dangerous to ride Red Clover "Slobbers" from fungal toxin slaframine is due to cholinergic effect of this alkaloid on salivary glands and tear glands
of this alkaloid on salivary glands and tear glands Causes bloat, frequent urination, watery diarrhea Alsike Clover Photosensitization, depression, stupor, liver damage Lining of eyelids become red and swollen Inflammation and lesions of the muzzle, mouth, tongue, eyes, eyelids, and ears, with discharge from the lesions Brownish urine, clay-coloured feces Sweet Clover For hay in prairies, on roadsides in Ontario Coumarin converted by hold to dicoumarol, which inhibits vitamin K in blood clotting OK if not mouldy, slight vanilla smell Crownvetch Roadsides, erosion control Slow growth, paralysis, death from nitroglycosides Sorghum and Sudan Grass Growthy annual grass, providing large yield for cattle Cyanogenic glycosides release cyanide, especially after wilting, trampling, frost, or drought Don't feed fresh or as hay to horses Oxalate Poisoning Several tropical grasses: buffelgrass, pangola, kikuyugrass, rhubarb Excess mobilization of Ca from bones due to low dietary Ca Demin bones become misshapen: lameness and "big head" in horses Rhubarb and other vegetable leaves are high in oxalates. May be accompanied by anthraquinone glycoside Other Plants to Avoid Brassicas: kale, rape, turnips Buckwheat: photosensitization Ryegrasses if infected with bacteria or fungi Alfalfa if infected with blister beetle Some haulage or silage if infected with Clostridium Nitrate and Nitrate Poisoning High soil nitrate is concentrated in plants (annual grasses) Nitrate converted to nitrite in horse cecum Drought and first both accelerate nitrate Within 0.5-4 hours of ingestion: pain (tucked abdomen), frequent urination, diarrhea, dyspnea, tachycardia, and brown discolouration of mucous membranes
of mucous membranes Tremors, ataxia, and belligerence which can progress to collapse, coma, and occasionally convulsions Nitrite oxidizes iron in hemoglobin to Fe3+ (ferric) which has less affinity for oxygen, making methemoglobin "blue baby" syndrome in humans Awful Aquatic Plants Blue-green algae: very common in stagnant and hot water Nervous form: tremors, not moving, difficult breathing, collapse, convulsion, death Hepatic form: weakness, pale mucous membranes, mental derangement, bloody diarrhea, death Blue-green algae survivors lose weight and have photosensitivity Prevention: don't use water from stagnant ponds in hot weather Beastly Bushes and Vicious Vines: Yew Contains taxing alkaloids which attach cardiac myocytes: heart failure and death Boxwood (landscaping plant): alkaloids, respiratory failure Burning Bush (flaming red in late autumn): colic, diarrhea Do not let horses eat any ornamental plants, flowers, bushes, or trees
of this alkaloid on salivary glands and tear glands Causes bloat, frequent urination, watery diarrhea Alsike Clover Photosensitization, depression, stupor, liver damage Lining of eyelids become red and swollen Inflammation and lesions of the muzzle, mouth, tongue, eyes, eyelids, and ears, with discharge from the lesions Brownish urine, clay-coloured feces Sweet Clover For hay in prairies, on roadsides in Ontario Coumarin converted by hold to dicoumarol, which inhibits vitamin K in blood clotting OK if not mouldy, slight vanilla smell Crownvetch Roadsides, erosion control Slow growth, paralysis, death from nitroglycosides Sorghum and Sudan Grass Growthy annual grass, providing large yield for cattle Cyanogenic glycosides release cyanide, especially after wilting, trampling, frost, or drought Don't feed fresh or as hay to horses Oxalate Poisoning Several tropical grasses: buffelgrass, pangola, kikuyugrass, rhubarb Excess mobilization of Ca from bones due to low dietary Ca Demin bones become misshapen: lameness and "big head" in horses Rhubarb and other vegetable leaves are high in oxalates. May be accompanied by anthraquinone glycoside Other Plants to Avoid Brassicas: kale, rape, turnips Buckwheat: photosensitization Ryegrasses if infected with bacteria or fungi Alfalfa if infected with blister beetle Some haulage or silage if infected with Clostridium Nitrate and Nitrate Poisoning High soil nitrate is concentrated in plants (annual grasses) Nitrate converted to nitrite in horse cecum Drought and first both accelerate nitrate Within 0.5-4 hours of ingestion: pain (tucked abdomen), frequent urination, diarrhea, dyspnea, tachycardia, and brown discolouration of mucous membranes
of mucous membranes Tremors, ataxia, and belligerence which can progress to collapse, coma, and occasionally convulsions Nitrite oxidizes iron in hemoglobin to Fe3+ (ferric) which has less affinity for oxygen, making methemoglobin "blue baby" syndrome in humans Awful Aquatic Plants Blue-green algae: very common in stagnant and hot water Nervous form: tremors, not moving, difficult breathing, collapse, convulsion, death Hepatic form: weakness, pale mucous membranes, mental derangement, bloody diarrhea, death Blue-green algae survivors lose weight and have photosensitivity Prevention: don't use water from stagnant ponds in hot weather Beastly Bushes and Vicious Vines: Yew Contains taxing alkaloids which attach cardiac myocytes: heart failure and death Boxwood (landscaping plant): alkaloids, respiratory failure Burning Bush (flaming red in late autumn): colic, diarrhea Do not let horses eat any ornamental plants, flowers, bushes, or trees
