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Can Grazing Eliminate Weeds?

Lewistown, MT heifer eats Canada thistle in pasture.
To read more about how to teach livestock to eat weeds, click over to this Special Collection of On Pasture articles and links to videos showing the process in action.

Before I started On Pasture, I was best known for having invented a method for teaching cows to eat weeds. The process is based in behavior science and is very simple. In as little as 8 hours spread over 10 days, anyone can teach their livestock to add a new weed to their diet.

It turns out that weeds are very nutritious, often better than grass. Once cows understand that food can be more than grass, they eat the new weed and then add more weeds on their own. They also train their offspring and herd mates. So, by training one small group you can end up with a whole herd of weed-eating animals in a very short time.

Over the years, I’ve spent a lot of time helping farmers and ranchers learn about this technique. One of the most commonly asked questions is “Can grazing eliminate weeds?” Here’s the answer, starting with a question.

“Can we eliminate weeds?”

The history of our war on weeds is long. On this continent we have legislation going back to the 1700s regarding the elimination of weeds. The 1934 “Book of Knowledge” handed down to me by my Grandfather puts it this way:

“It has been said that the weeds of the earth are one of the most formidable agents ever established for man’s overthrow. It is only as he conquers them that he rises.  Man in the physical sense, is but a weakling, and when he lets nature in the fullness of her powers overtake him, he is well-nigh at her mercy.

“By some sinister provision they are marvelously fecund. Under drought and neglect they thrive. When man ignores them they rise to the height of their powers.”

(Vol. 9 pg. 3392)

So far, no one anywhere has eliminated a weed with pesticides, with insects or with grazing. The problem is that we have a seed bank in the soil that provides new seedlings, and every year, in spite of our best efforts, more seeds are added to the bank. This makes managing weeds something like managing the hair on your head: You can get one really great haircut, but don’t expect it to last the rest of your life. Chances are good that you’re going to need another haircut in a month or two. In the case of weeds, you’re always going to have to do something to manage them.

With our long history with weeds, thinking about calling a truce is hard. But maybe it would help if we think of weeds in a new way. Generally we label plants that are considered to be nuisances, or that are unwanted in gardens or agricultural areas as “weeds.” But once your cattle are eating them are they still a nuisance? What if weeds became Forage?

Weeds are very nutritious!

Weeds can have many beneficial qualities. Many are as nutritious as alfalfa. Here’s just a small sampling of very nutritious weeds:

This weedy protein can actually help when it comes to grazing low quality, dormant grasses. As ranchers in the west know, adding a protein supplement tub to a dry pasture gives rumen microbes just what they need to convert roughage into digestible protein for the cow. Weeds that are often still green and growing when grass has senesced, can perform the same service to microbes needing that extra boost.

Weeds are always there for you!

In addition to being nutritious, weeds are often available when other forages aren’t, either because of the time of year or due to drought conditions. During the drought of 1934-1939 Russian thistle provided a large part of the grazing for small ranches and farms. It makes senses when you realize that its protein levels include a high of about 25% in May, only dropping below 10% during the winter months. Many ranchers in the west also look forward to the early spring and late fall green up of cheat grass, one of our most aggressive annual invaders, because it comes at a time when other forage is scarce.

Finally, grazing weeds can increase how much forage you have. Economist John Morley found that, based on average pasture weed populations, if a producer’s cattle ate just 70% of the weeds available, that producer would have about 43% more forage. This is just an average and your percentage will be different based on your past weed management practices.

Grazing can make weed management easier.

There’s no doubt that grazing can change vegetation. The way we managed our grazing in the early 1900s helped to reduce populations of perennial grasses in some areas of the country, even when that wasn’t our intent. We simply grazed the same area too often to too short a stubble height until the plant could no longer compete.

Lewistown, MT heifer eats Canada thistle in pasture.

It’s that kind of grazing that will also help us control weeds. There are many studies indicating that yes, grazing can, at a minimum, reduce the vigor and spread of weeds. For example, scientists found that grazing diffuse knapweed in the bolting stage reduced the number of plants by 50% and reduced seed set by 50% as well. In fact, most grazing prescriptions for weeds focus on preventing seed set by grazing multiple times in a season. If this works with your animal and vegetation management goals, then it’s a potential avenue for eliminating your weed problem.  Just be sure that the forage you’d like to protect isn’t being damaged in the process.

If a little less intensive management plan suits your goals or the time you have available, don’t despair.  It will just take a little bit longer for your weed population to change.

In the end, weed management is about your goals and how much time and money you have to spend on getting there. Grazing can be a useful tool for reducing the amount of money you have to spend and may even give you a chance to reevaluate whether you’re really interested in carrying on a war that we haven’t won for generations.

Want More?

How to Teach Cows to Eat Weeds in Just 8 Hours Over 7 Days

And here are more resources:

Turn Your Livestock Into Weed Eaters


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