Cattle generally stay away from the yellow oleander plant when it grows in an open, green pasture. But when hay's harvested, the plant can mix into the diet. That lays a heavy burden on farmers and cattle owners to keep it out of the food supply, because all parts of yellow oleander -- leaves, blooms, stems and seeds -- are toxic to cattle, fresh or dried. Cattle who ingest yellow oleander may become sick and die.
Yellow oleander generally enters a cow's digestive system through her mouth, thanks to the feed production process. Oleander contains chemicals called glycosides. Once in the system, these chemicals become toxic, causing heart failure or respiratory paralysis. When hay or silage is gathered, yellow oleander can wind up in the bales or bins, inadvertently mixed in. When feeding, the cow ingests the toxic plant, which in turn causes yellow oleander poisoning. The degree of poisoning depends on how much of the plant the cow ingests.
Signs and Symptoms
Signs and symptoms of toxic poisoning may vary. After ingesting yellow oleander, the cow may show signs of abdominal issues, like diarrhea. Also, the cow may experience drooling, paralysis and the loss of muscle control. Clinical signs, such as an increased or decreased heart rate or abnormal electrolytes, may help a veterinarian diagnose yellow oleander poisoning as well.
Ingesting as little as 0.005 percent of body weight, or between 10 and 20 leaves, can kill a 1,500-pound cow. However, for slight poisoning, the signs of poisoning often dissipate after removing the cattle from the infected forage. However, in severe cases diagnosed early whereby the cow’s life is in danger, the antidote -- digoxin-specific "Fab" fragments, a sterile lyophilized powder made from antibodies and immunoglobulin fragments -- offers hope when administered by a vet. However, it is an expensive option, according to the Pet Poison Helpline website.
Since cattle cannot differentiate the dried leaves or blooms of oleander from their food, it is important that the individuals baling the hay or making the silage pay attention to the material going into them. Walk the field before cutting the hay and pull or dig up any oleander by the roots you find. Cutting the oleander off will not kill the roots and it will regrow. Check the hay again for leaves or stems of oleander before baling it. Also, checks crops before cutting silage and make sure no yellow oleander is growing.
When purchasing hay from an individual, ask if any oleander has ever been found in the pasture. Examine the hay and silage personally before feeding it. If any pieces, dry or wet, of yellow oleander are found, dispose of the product, since it is also toxic to other livestock such as horses and sheep.