Some time ago, I got this email from Jamie in Nebraska:
I am interested in your way of controlling leafy spurge with cattle, however, I was informed that leafy spurge was toxic to cattle. I guess my question is how much can they eat before they become sick? I have a 600 acre sub-irrigated meadow out here in the Nebraska Sandhills in which I have several populations of leafy spurge ranging from dense 23 acre sites to scattered stands covering 20-30 acres. I would really like to use my cattle for this simply because it would be cheaper for my operation and spraying is really not an option due to the fact that I have three endangered species and I am located around a lot of water, not to mention I am sitting on the Ogallala Aquifer. What are your suggestions, if any?
Here’s my answer:
It’s not really true that leafy spurge is toxic to cattle.
When I first started teaching cows to eat weeds in 2004, I had heard a lot of the same information that you may have heard about leafy spurge. Sheep and goats can eat it but cows can’t. The sap can cause irritation or burning in the mouth and digestive system, skin irritation and diarrhea. This basic sentence is included in most texts on leafy spurge.
On the other hand, I knew that cows on the Rex Ranch in Nebraska were eating spurge. So, in spite of the warnings, but with a healthy dose of caution, I went ahead with trying to get cows to eat leafy spurge.
Cows successfully ate leafy spurge from tubs during training in 2004. We weighed them once a week to ensure they were healthy and as part of that process we checked their mouths for signs of irritation or lesions. There were none. They also never suffered from diarrhea. But, I wasn’t able to try them on the weed in pasture until the summer of 2005. I was working at a National Historic site and it took a year to get permission to graze cattle in the riparian area where most of their leafy spurge.
In 2005, cows grazed in leafy spurge pastures in June and in August. They demonstrated that they could and would eat leafy spurge in pasture and I was still seeing no negative effects. They stripped leaves and flowers from the stalks, and once I let them out into the newly-mown hayfield adjacent to the trial pasture, they returned to finish off the patch of leafy spurge they had been working on. Though I have only anecdotal evidence, I observed that when the cows had more variety they ate more spurge, and when I put them in trial pastures with less variety, they ate less leafy spurge.
What a learned from teaching other cattle to eat leafy spurge reinforced the idea that variety is important. In 2009 I worked with a rancher in Montana to train cows to eat spurge. The pasture his cattle were in was primarily leafy spurge with a little grass scattered here and there. It was so bad that he had considered spraying it with round up, then scraping it off, and starting from scratch. Though the trained cattle ate some of the spurge, they didn’t do nearly as well as cattle grazing in a pasture with forages other than that weed.
This requirement for variety makes sense based on research done by Dr. Fred Provenza and his colleagues at Utah State University showing that nutrients and toxins can in one plant can offset the effects of toxins in another. They also learned that when animals could mix a variety of forages, they were unlikely to eat too much of a plant containing a toxin that is harmful at a higher dose.
Other Graziers Have Had Success With Leafy Spurge Too!
In 2007, Lester Pryce, Saskatchewan’s Prairie Farm Restoration Administration Community Pasture Land Manager, decided to try my training process on leafy spurge. He was surprised at the willingness of the cattle to eat spurge in training and at calf behavior.
“If green crested wheat and leafy spurge were put in a tub, often the calves would eat the spurge and leave the grass.” When the cattle were left to graze a 30-acre pasture to 50% utilization he found that every leafy spurge plant had been grazed to some degree.
Pryce said of his experiment, “We learned that it is definitely possible to train cattle to eat new foods using Kathy’s cattle training process, and that there may be a possibility for producers to develop a very low cost method for training cattle to consume problematic weeds on our rangelands.”
Here’s an email I received from Silena and Warren Koster of Clinton BC,Canada:
Subj: B.C. Cattle Co. LTD Heifers loving Leafy Spurge
We just wanted to fill you in on our progress with teaching/introducing weeds to our cattle.
My husband Warren set about in June with the replacement heifers and a small group of 1st time calved heifers and their calves, to introduce the leafy spurge. It was so lovely to see the cattle bucking and twisting, racing to him and the feed tubs. It took no longer than 7 days. The heifers are now in an enclosure of leafy spurge/grasses/shrubs with their bulls before turning out on range. We are so enthused by the simplicity of the whole idea, and how cooperative the heifers were about it. Thank you for all your dedicated research in this study and passion on your knowledge to others. My daughter, Camilla, and I attended your seminar in Williams Lake, last year.
Finally, you can read about Sue Kennedy’s leafy spurge training project here:
In Sue’s case, the cattle weren’t overly fond of the spurge during the second rotation through the pasture. This tells us that there’s something more we need to learn about helping animals graze this plant successfully.
So why do some scientists continue to say that leafy spurge is toxic?
One reason may be the same thing that makes science so reliable: learning from the work and information of others. In this case, all the citations I found eventually pointed back to one source, the 1939 “Poisonous Plants of the United States” by Walter C. Muenscher who related a story of leg hair loss on horses working in spurge infested grain fields. He provided no citation for this story, nor an indication of which type of spurge was involved. Now this story has been repeated numerous times, so I wonder if we started with inadequate knowledge.
Another reason that science is wrong about leafy spurge is that we haven’t always understood the important role variety plays in allowing animals to process nutrients and toxins. Thus, in some experiments, cows were “overdosed” with spurge. When they got diarrhea or went off feed, it was attributed to the weed, not the quantity or lack of variety.
Finally, sometimes we have too easily taken the cow at her word. If she doesn’t immediately eat something, we have assumed it is unpalatable without taking into account the role of learning and neophobia in animal diet choices. It would be like me saying, based on my observations, that only macaroni and cheese and hotdogs are palatable to 4-year-olds.
One last point: in my search to find out why leafy spurge was so harmful I found a paper by scientists who actually looked for the harmful effects supposed to be caused by leafy spurge sap. They found no lesions in “nasal passages, oral cavity, tongue, esophagus or viscera” of animals who had eaten leafy spurge.
Want to turn weeds into forage?
Here you go: