As grass pastures green up during spring, we often are on the lookout for weeds to control. Before actually trying to control these weeds, though, maybe we first need to decide what a weed is.

A common definition of a weed is a plant out of place or where it is not wanted. My dictionary defines it as a plant of no value or use. And when we look at our pastures, we often consider any plant that was not part of our original seed mix as a weed.

When I define what a pasture weed is, I use two criteria: not eaten by the animal or contains anti-quality components. This definition changes the perspective about what we define as weeds, as well as our entire attitude about controlling them.

Many annual grasses, like crabgrass, barnyardgrass and foxtails, are readily consumed by grazing livestock when the plants are young and vegetative. Even some perennial grasses commonly thought of as weeds, like quackgrass and johnsongrass, have high nutritional value, although johnsongrass can contain toxic amounts of anti-quality components – prussic acid and nitrates.

Some annual broadleaf plants also are grazed when young by livestock, including pigweed, kochia, morningglory and sunflowers. And I have seen cattle actually select perennial broadleaf plants like field bindweed and curly dock. However, anti-quality components like nitrates can be a problem in these plants, too, if there is a large patch of them that allows animals to eat a large amount in one meal.

Since many “weeds” are grazed readily by livestock, especially when these plants are young and vegetative, they actually may be a valuable feed resource. Research from California to New England, Louisiana to Minnesota and the Canadian prairies all show that many plants we call weeds are as digestible and contain as much crude protein as conventional forages such as alfalfa, bermudagrass and smooth bromegrass. However, their nutritional value as well as their palatability often decline more rapidly as they mature than do conventional forages.

So how do you take advantage of the feed value in your pasture weeds? First, identify the weeds you have in order to determine if they can be grazed safely, or even if it is likely that your livestock will graze these plants. If the weeds can be grazed safely, select sites within your pasture where weed grazing would be most beneficial and when these weeds are relatively young and more palatable.

Grazing livestock tend to be less selective when stock density is high and they are given a small area to graze for just a short period of time. Thus, best results will occur when you restrict animals to an area that provides no more than a couple days of grazing at a time. Not only will more weeds be grazed, but your desirable pasture plants will also recover faster after grazing due to the short grazing period in which they are exposed.

Another way to use this diversity in plant species is to add diversity to the livestock grazing your pastures. Cattle primarily prefer grass, but goats and sheep actually prefer to graze some of the plants that cattle ignore. Adding another species of livestock to your grazing herd can increase output from your pasture with little or no reduction in production from your primary animals because they eat different plants.

Note again that in order to turn pasture weeds into feed, the weeds usually need to be young and palatable. They need to be safe to graze or be present in small enough amounts that livestock will not be able to consume enough of them to experience health problems. And animals should be encouraged to graze the weeds by placing many animals in a small area for a short time period.

Of course, grazing isn’t the complete answer to all weed problems. There are poisonous plants that are very hazardous to graze, and there are plants that would require an excessive amount of training or management to get livestock to graze. When pastures have an abundance of these types of weeds, control methods besides grazing may be needed if reducing the amount of these plants is desired.

But don’t automatically reach for herbicides when weeds appear in your pastures. First see if you can turn them into feeds, saving money and maybe even increasing production.  FG

Bruce Anderson is an extension forage specialist with the University of Nebraska – Lincoln.