Toxic pasture weeds can harm horses

By Tina Booton
Weld County Public Works

Horses are a part of the Colorado landscape--as critical to many as water, air and food. That is why it is so important to keep them safe.

Safety includes knowing what horses are eating. The green plants in pens and pasture may not be as safe as one would think. The following plants are some of the more toxic plants in Colorado's pastures.

Leafy spurge, field bindweed, yellow sweet clover and alsike clover can increase skin sensitivity to light or cause colic. Horses will generally eat other vegetation than these plants if available. However, these plants are very aggressive and tend to overtake a pasture.

Gumweed, penstemon, prince's plume, saltbush, woody aster and some milkvetch species are selenium accumulators. When a horse consumes these plants the selenium replaces the sulfur that is needed in keratin formation. Keratin is the primary protein in the hoof and hair. Extended ingestion can cause permanent damage and may cripple a horse for life.

Senecio and houndstongue produce similar symptoms. These include diarrhea, red urine, sensitivity to light, circling and weight loss. There is no treatment for the liver disease.

Russian knapweed and yellow starthistle produce symptoms including frozen facial muscles, excessive salivation, severe weight loss, inability to chew or drink, or drooping look to the face and lips. There is no treatment for these poisonings, and euthanasia is recommended.

There are three species of locoweed: purple, white and wooly. The poisoning symptoms from these species include abortions, weight loss, depression, excessive sleeping, or violent reactions to routine items. There is no treatment for locoweed poisoning.

Sand and fringed sage have very similar poisoning indicators to the locoweeds, with the addition of a sage smell to the breath and feces. Remove horses from the sage plants and feed a nutritious diet. The horses should be able to recover if given proper support as needed.

It is imperative to manage pastures for good grass growth and competition against these dangerous plants. This may mean that the horses will need to be removed from the pasture for it to rest and recover. It may also be necessary to reseed the pasture for good grass growth. A noxious weed management plan may be needed to evaluate the best options for addressing pasture weeds.

The first step is to identify all plants in the pasture. Once this step is completed, it is possible to make the choices that are needed to enhance the vegetation as well as protect horses.

For more information and help in identifying vegetation go to www.weldweeds.org. Weld County residents should call 304-6496, extension 3770, to schedule an appointment. Larimer County residents should call Jennifer Gorek, senior weed specialist, at 498-5768 or visit the web site www.larimer.org/weeds.