Russian knapweed (Centaurea repens) is a perennial weed that has proven to be expensive and difficult to control. In fact, it’s very resilience led researchers at Oregon State University to see how it might be used as a forage. Their results shows that it’s high in nutritional value, generally similar to alfalfa, and that cows and in fact there was no difference between alfalfa or Russian knapweed when they were used to supplement other low-quality feed. The the 2006 paper by Bohnert et al concludes with: “Thus, haying Russian knapweed in the spring and feeding in the winter may provide an alternative to controlling of large scale infestations.” Or – if you can’t beat it, eat it!
Russian knapweed is toxic to horses if they consume 60 to 70% of their body weight of the plant. The sesquiterpene lactone “repin” seems to be responsible for the problem in horses. Symptoms of the resulting “chewing disease” include a stiffening of the muscles used to pick up and chew food, giving the horse a “wooden” expression. Animals may hold food in their mouths attempting to chew and the saliva may cause froth around the mouth, giving them the appearance of rabies. There is no treatment for this poisoning and animals will die as a result. Be sure that pastures where horses graze have plenty of variety so that they are not forced to eat Russian knapweed.
The University of Idaho’s Targeted Grazing website notes that it takes repeated, intensive grazing over a period of years to significantly reduce this plant. They recommend removing 80% of the plant, three times per season, allowing 8 to 10 inches of regrowth between grazing treatments and repeating this for three or more years successively.
This prescription seems almost impossible for a producer to achieve and would likely put a high level of stress on any other forages growing in the vicinity. So I recommend looking at the plant in a different way. A plant that is as nutritious as alfalfa and can regrow 8 to 10 inches between grazings may be something that does not need to be eradicated. At the same time, a solid stand of this plant is not desirable either. We know that the plant is not shade tolerant and that when other forages have less stress on them, they will compete well with the Russian knapweed, and can even shade it out. Given that information, I would graze it at times that would stress it, and provide other forages with opportunities to grow. I would not go to the trouble of trying to eradicate this plant.
Want Your Livestock to Add Russian Knapweed to Their Diet? Our article “How to Teach Livestock to Eat Weeds” will give you the basics. Or you can visit my Livestock for Landscapes website to order books and DVDs that will teach you how to teach your animals.
When it was decided that cows had to be “babied”, to increase production, we diminished their innate knowledge to live off the land and eat whatever grew there. A cows knowledge can be turned back to what is natural and that makes her so much more efficient. She doesn’t know any different if she is eating nutritious weeds instead of alfalfa hay. This is what she was designed to do! We have to take a step back and study nature, and then work with the cow to build on that knowledge without making her dependent on us for her well being.
Good article Kathy. It is very pertinent to a situation that i’m advising on right now. My nephew owns 200 acres north of Alamosa that is infested with Russian knapweed but has a fair component of perennial native grasses and some fourwing saltbush. He and his father have tried mowing and some spraying to control it but with no or very limited success. He bought are a few head of heifers this past spring to pasture on his place and we used your techniques to train the heifers to eat the knapweed. It worked pretty well this summer. I’d say the heifers eat about 30-40% of their diet was the knapweed so we thought that was fair success. He’ll need to repeat the training on the new cattle he brings on the place next spring. But anyway, thank you for developing the training protocol for us…! We’ve definately turned these feifers in weed eaters thanks to you!
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