The risk of grazing animals being poisoned by hemlock may be greater than normal this year, but graze intelligently and losses can be avoided, advises Bruce Anderson, University of Nebraska-Lincoln (UNL) Extension forage specialist.

Hemlock are tall weeds with umbrella-like white flowers usually seen in moist areas of pastures, particularly along streams, roadsides and grasslands. Poison hemlock and its cousin, water hemlock, are two of the most poisonous of all flowering plants.

Fortunately, hemlock usually isn’t palatable to livestock, Anderson says, and animals won’t eat much of it unless very hungry or the plant has been altered in some way. That means it’s critical that overgrazing pastures that contain hemlock be avoided.

“When adequate forage is available to graze, animals select healthy, palatable plants to eat and avoid the hemlock. But if grass gets short, even unpalatable poisonous plants might be eaten,” Anderson says.

This includes turning hungry animals into fresh pasture containing hemlock, since some hungry animals will eat the first green plant they come to when very hungry, palatable or not. Also make sure plenty of water, salt, and mineral always are available. Animals deprived of water or mineral may eat abnormally, increasing the risk of consuming some hemlock, he says.

Anderson strongly warns against trying to control hemlock during the grazing season by clipping or spraying. This practice alters the plant and actually can increase its palatability, making it more likely that animals will eat enough of it to cause poisoning.

Editor’s note: Steve Boyles, Ohio State University (OSU) Extension beef specialist, offers these producer guidelines to minimize livestock illness from poisonous plants:

• Learn to identify poisonous plants.
  
• Supplement feed with salt, minerals and other nutrients.
  
• Avoid grazing animals in areas of abundant poisonous plants.
  
• Provide adequate water to prevent non-selective grazing.

• "Why Animals Die From Eating Poisonous Plants" – www.behave.net/fact_sheets/PoisonousPlants.pdf.
  
• Poisonous Plants Section from OSU's Horse Nutrition Bulletin 762-00 – ohioline.osu.edu/b762/b762_24.html.
  
• University of Pennsylvania – cal.vet.upenn.edu/projects/poison/index.html.
  
• Cornell University – www.ansci.cornell.edu/plants/index.html.
  
• www.beefcowcalf.com – type "poisonous plants" into the "Search For" box on the opening page.