Not all plants are wholesome for foraging animals.
Certain species of milkweed, for example, that are highly valued as host plants for the dwindling monarch butterfly population, are extremely poisonous to pets and to range animals like sheep, cattle and goats. Even free-ranging chickens aren't immune. Among potentially toxic poultry pickings are castor beans and certain mushrooms, although chickens don't eat them as readily as do animals.
Plant toxicity is directly related to dosage. How many were eaten, how healthy was the animal, how long do the toxins persist and what can be done?
Some plants, like water hemlock, "can kill a cow in 15 minutes, while others, like buttercups, just leave a burning sensation in their mouths or tongues," said Donna Foulk, an Extension educator with Penn State University.
Ornamental plants either in or outside the home are frequently toxic, she said.
Animal poisoning can be tough to diagnose, but symptoms range from difficulty breathing to refusing food, blistering and skin lesions to dizziness and diarrhea. Call a vet immediately if such conditions arise.
Many weed varieties aren't toxic unless environmental conditions make them so. "If plants pick up a lot of nitrogens from rain and rapid growth, and animals eat a lot of them, they can die," said Mark Renz, a University of Wisconsin Cooperative Extension weed scientist.
The problem becomes even more acute during dry weather when pasture grasses go dormant and troublesome but persistent weeds become more enticing as fodder.
Most of those weeds are unpalatable to animal taste buds but often are eaten when dried and mixed with other materials, like in a hay bale.
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