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cattle on pasture

A small amount of water hemlock can kill a cow, especially if the root is eaten.

Toxic Plants

Different regions have different problem plants.

Different regions have different problem plants; plains and prairies have some poisonous plants that don’t grow in the mountains and vice versa.

Some problem plants can be safely eaten in small amounts or certain stages of growth, while others are toxic at all times. Cattle poisoning often depends on palatability (some plants are rarely eaten), stage of development, portion eaten (some have more toxin in roots, seeds or leaves) and growing conditions.

hay for export

Death camas is native in the northwest.

Rachel Turnquist, forage extension specialist in Saskatchewan, says the main issues are identification and management.

“You need to know which plants are a problem in your pastures, and a general idea where different ones might be located. Some might be in wet areas (water hemlock, wild parsnip and poison hemlock, for instance),” she says.

“If you are using native pastures, you might be surprised at how many toxic plants are out there. The main reason we don’t see more poisonings is that generally cattle won’t eat them. Making sure you have healthy, vigorous pastures (not overgrazing) decreases risk for poisoning. Most poisonous plants are avoided by cattle unless there isn’t much else for them to eat,” says Turnquist.

It’s a different story cutting a field for silage or putting up hay. In hay or silage, cattle are less likely to sort out the poisonous plants, she explains. Before cutting a field, especially where there may be wet areas, get out and walk through those and familiarize yourself with the plants before you cut it for hay or silage.

In drought conditions certain plants accumulate nitrate. Some plants accumulate selenium, which can be toxic in overdose, she adds.

“Poison hemlock is toxic, especially in the spring. It only takes a couple hours between eating it and death. Water hemlock is even more toxic. It only takes a small amount to kill a cow, especially if they eat the root,” she explains.

Wild parsnip is also a problem in some areas.

“If a person touches it, they often develop severe rash. If cattle eat it, contact with the mouth tissues can give them oral dermatitis and a painful mouth,” says Turnquist.

hay for export

Larkspur is readily eaten by cattle and is responsible for many cattle deaths each year.

Patches of tall larkspur in mountain meadows and wet areas kill many cattle every year because cattle readily eat these plants. Some years, larkspur is more deadly, due to different growing conditions, and on a dry year these plants may be the greenest thing in the pasture.

To avoid problems, the key is to manage for vigorous pastures so cattle are never short on feed.

“Also take time to walk around your hayfields to know what is growing out there. You might be able to get rid of patches of toxic plants, depending on what they are, or avoid cutting those areas for hay, or fence them off from grazing,” says Turnquist.

If cattle eat some of the more toxic plants, you rarely have a chance to find them in time to try to treat them; you just find them dead.

“Some plants won’t instantly kill a cow, but you still might not find poisoned animals in time. Some plants’ toxic effects are cumulative. Common tansy is an invasive noxious plant that if eaten by cattle over time will cause liver damage or abortion. You might not see any problems until it is too late,” she says.

If you find a dead animal, you can’t just assume it died of plant poisoning, however. Consult with your veterinarian for diagnosis. If you need help to figure out which poisonous plants you have, talk to your local Extension agent or an Extension range management specialist, she says.

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Editor’s Note: Heather Smith Thomas is a cattlewoman and freelance writer from Salmon, Idaho.



 

 

 

 

 

 





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