Learning to identify plants poisonous to cattle

Timing and location Toxic plants are more 
dangerous in the spring and alongside waterways

Reading Time: 3 minutes

On the banks of the Beaver, where seldom if ever, any poisonous herbage doth grow.” That description from one of the lesser-known verses of “Home on the Range” is pretty much true in Alberta, but there are a few nasty plants out there, says Donna Lawrence, boreal forest specialist with the Rangeland Management Branch of Alberta Environment.

Lawrence told the annual Grazing School for Women that producers should know which plants, and which parts of them, are poisonous. In some cases, seeds, leaves or roots can be the problem.

It’s a good idea to avoid early-spring grazing areas in riparian areas, Lawrence said. “If you stick your cattle out there then, the riparian area is generally the only place that’s green. This is where they’re most likely to come into contact with poisonous plants.”

It’s also important to manage riparian areas during drought because livestock will be attracted to these areas, and will graze even closer to water bodies, where poisonous plants can be a bigger threat.

When forage health and diversity are maintained, poisonous plants will not take over an area, as they will have other plants to compete with. “When there are other plants out there, the actual chance of them running into that poisonous plant is pretty slim,” Lawrence said.

Elephant’s head is another plant that can be toxic if consumed in large quantities. Cattle that eat it might also become more susceptible to lice, fortunately its unpalatable and rare. “They’d have to eat a huge schwack of it to be affected,” Lawrence said. Some species of buttercup can be an irritant to the skin of livestock. The irritant declines when buttercups are dried, so they are not irritants when they are found in hay.

Horsetails are common in moist areas, and are a component in meadow hay. These plants can be a problem for young horses, as horsetails contain a toxin that can affect the way horses process thiamine. Horses affected by horsetail will develop flu-like systems, appear weak and lose weight. Horses need to eat a large amount of this over a long time before they get sick.

Saskatoon leaves have some cyanide in the young growth, but animals have to eat a lot of it in order to be poisoned. In order to reduce risk, producers can wait until late in the growing season to graze Saskatoons. “There are way more cows grazing Saskatoon than ever get poisoned by Saskatoon,” said Lawrence.

Tall larkspur can be a problem. It also greens up early in the spring. The leaves are poisonous early in the season, and then the poison transfers to the seed. If it is grazed later in the season, the poison can usually be avoided.

Locoweed is a plant found on grasslands. Cows have to eat a large amount over a long period and will appear stoned if they eat it.

Seaside arrowgrass is appealing to cattle because it accumulates salt. It is common in riparian areas and will green up before many other riparian plants. Making sure cattle are well watered and well salted will help keep them away from this plant. Seaside arrowgrass can also appear in native hay.

Water hemlock is a native plant that also shows up in wet areas. The plant is severely toxic to both livestock and humans. The toxins build up in the roots and tubers. Anyone who finds water hemlock and decides to remove it needs to wear gloves and dig the plant out of the ground in the fall. These plants do not form large mats, but appear as individual, isolated plants. Water hemlock looks similar to water parsnip, which is common and innocuous.

About the author


Alexis Kienlen

Alexis Kienlen lives in Edmonton and has been writing for Alberta Farmer since 2008. Originally from Saskatoon, Alexis is also the author of two collections of poetry, a biography, and a novel called "Mad Cow."



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