Canada Thistle is Alfalfa’s Equal

Canada thistle (Cirsium arvense) is most often compared to alfalfa for its nutritional quality.  A breakdown of its crude protein was provided by Oregon State University of 21% in the Spring, 13% in Summer and 12% in the Fall.  Such high protein values make it quite palatable all season long. Animals should especially like it in the summer when grasses are beginning to dry and are losing their protein values. Kathy Voth has trained over 1000 cattle and a small herd of bison to eat this tasty weed, so we give it a big thumbs up as a forage. Grazing Canada thistle  According to Kathy, this is one of the easiest plants to teach cows to eat.  While people worry about the spines on the plant, she has not found these to cause problems for the animals or to prevent them from eating it.  She says, “No Canada thistle-eating cow has ever suffered an illness or injury as a result of grazing this plant, but that’s because I have taken the necessary precautions to make it safe." While the spines are not a problem for grazers, the potential for nitrate accumulation in the plant is.  The problem with nitrate accumulators is not the nitrate itself, but the chemical process that takes place in the rumen.  Nitrate is reduced in the rumen in a series of steps from nitrate to nitrite to ammonia and finally to microbial proteins.  It is the nitrite in this step that causes poisoning if it accumulates in large amounts.  When the animal has carbohydrates in its rumen, nitrate

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2 thoughts on “Canada Thistle is Alfalfa’s Equal

  1. 6/30/13 I just mowed 20 acres that beef and horses have been on. There were a few Canadian thistles other years, but today there were solid patches 4′ high, about 20% in bloom. It was seeded with brome and alfalfa 12 yrs. ago and in CRP for 10 yrs. before that. Now it is mostly what we call sod bound, except there were patches of creeping charlie. A brick yard adjoined this farm, which has the same clay. I’ve spread a lot of organic matter on this field, in that town people have been dumping compostables here for 21 years, the cattle are fed on the huge pile all winter and I push it with a large dozer, so only part of it heats. We’ve had an unusually cold wet May and June. Do you think there will be a problem feeding round bales, some of which will be almost totally thistle? I’m organic and would rather not dig it. Is there anything I could no til into it, that could compete with the thistle. I’ve spread the same organic mater on another field, that had no bare/creeping charlie patches and heavy sod and no thistles have appeared there. Thanks for any suggestions.

  2. One of the comments on our facebook page was from a fellow whose cattle weren’t eating their thistle in their night pasture. He and I will talk shortly so that I can help him solve this problem, and I wanted to share some information here for those I may not get to talk to individually.

    One of the issues with a plant that is as high in protein as Canada thistle (or alfalfa) is that an animal can only eat so much of it before it needs to eat something else. For example, I’ve watched cattle in pasture eat lots of thistle, and then head for yellow, dried out cheat grass to balance the high protein with some roughage.

    My rule of thumb is that if an animal isn’t eating something that I know is nutritious, it’s my job to figure out what I need to change in my management. Does the animal need some education? Is it the timing of when something is being grazed? Have I taught them to expect that I’ll move the herd soon so that they don’t have to clean their plates?

    I’ll be sharing more about this in coming articles. Stay tuned!

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