Are Oregon Grape Plants Poisonous to Cows?

Cows could possibly become ill as a result of eating large quantities of Oregon grape, but there are no documented cases of cattle dying after ingesting this plant. While there have been a few anecdotal accounts of cattle dying after eating Oregon grape, neither the United States Department of Agriculture nor the ASPCA has found evidence enough to warrant listing the plant as toxic to livestock.

  1. Toxicity

    • Oregon grape is rated "non-toxic" by the ASPCA, the California Poison Control System and the University of Utah's Poison Control Center.

    Consumption by Humans

    • Oregon grape is commonly used as a food supplement by humans. According to the website Herbal Extracts Plus, high concentrations (many times the recommended levels) can cause nose bleeds, skin and eye irritation, sluggishness, diarrhea, vomiting and kidney inflammation.

    High Doses

    • Given that very high doses of Oregon grape can be harmful to humans, it is possible that high dosages could lead to similar effects in cattle, but huge quantities would have to be consumed before similar concentrations could build up in the cow's system.

    Likelihood of Cattle Consuming Large Quantities

    • It is highly unlikely that such extensive overgrazing could occur: alkaloids in the leaves act as a defense against grazing, rendering the leaves distasteful to animals. To date, no USDA environmental study has found a preference by cattle for Oregon grape.

    Hypothetical Explanation

    • Many explanations are possible for the stories of cattle dying after eating Oregon grape. If we are to believe that the cattle died solely as a result of eating this plant, then we must assume these deaths occurred in situations of extreme overgrazing, possibly in the absence of other edible foliage. Oregon grape does grow in dry climates, and the most often noted of these cattle deaths did occur in Arizona. In a drought or near-drought situation, Oregon grape may have become the primary food source for these stricken cattle. Unfortunately, we simply do not know the full details of these deaths, and there have been no recent cases by which to verify this hypothesis.

    Other Names

    • The scientific name for Oregon grape is Mahonia aquifolium. Other common names include Oregon grape holly, mountain grape, Rocky Mountain grape, holly-leaved berry, California barberry, mahonia, holly mahonia and trailing mahonia.