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Exotic plants can be invasive and take over rangeland and pasture land. In Wyoming, yellow sweetclover (Melilotus officinalis) is an exotic legume introduced from Europe and Asia to the U.S. as a forage crop.  Yellow sweetclover has been documented to invade and dominate plant communities by outcompeting other herbaceous plants for resources.  Currently, yellow sweetclover is listed as “invasive” in 26 states, including Wyoming, by the Alien Plant Working Group. The use of strategic grazing with sheep has been suggested as a strategy to reduce invasion and dominance of invasive plants. However, no data exists documenting the preferential selectivity of sheep on sweetclover and the changes of sweetclover dominance and structure relative to other plant functional groups. 

In 2015 and 2016, we used two groups of sheep – Rambouillet and Hampshire/Suffolk commercial ewes – to strategically graze yellow sweetclover-invaded pastures at the University of Wyoming Agricultural Experiment Station Sheep Unit in Laramie. In 2015, there were 24 ewes plus lambs in each breed group, and in 2016 there were 21 ewes plus lambs in each breed group.  Pastures were eights acres in size, and sheep were rotated from June through August for approximately three-week intervals. 

As sheep moved into a new pasture, they were repeatedly observed to immediately select the yellow sweetclover plants, first by eating the flower blooms and then by eating the youngest leaves. We also conducted vegetation sampling before sheep entered a pasture and after sheep left a pasture by measuring abundance of grasses, yellow sweetclover, forbs or flowering plants and cactus and measuring the structure of the yellow sweetclover.  We were able to compare these measurements to pastures that had no sheep or cattle grazing but did have pronghorn present regularly.

We found no differences between breeds of sheep in how they changed the plant community composition. 

Before sheep grazing, relative abundance of yellow sweetclover was 33 percent. After sheep grazing, yellow sweetclover was reduced to seven percent, and in the control pastures with no sheep grazing, yellow sweetclover was 29 percent. 

In contrast, before sheep grazing, relative abundance of grasses was 61 percent. After sheep grazing, grasses were increased to 91 percent, and in the control pastures with no sheep grazing, grasses were 65 percent. 

Our sheep grazing treatments reduced elevated leaves on yellow sweetclover from 100 percent to less than 20 percent, reduced the height of yellow sweetclover plants by 50 percent and reduced the number of flowering stems per plant from 14 per plant to less than one per plant. 

The reduction in flowers is important because these are the reproductive plant parts that produce seeds.

So, as we deal with invasion of exotic plant species, sometimes we can employ sheep to use their flexible dietary preferences.  We will continue to investigate this project to see if the results in the growing season lead to long-term reductions. 

For more information contact me at This email address is being protected from spambots. You need JavaScript enabled to view it. and check out my blog ‘Rangelands4u’ at

“Grazing cover crops that contain moderate to moderately high nitrate concentration is not without risk, but these cover crops can be grazed successfully,” said University of Nebraska-Lincoln Beef Systems Specialist Mary Drewnoski during a presentation of managing nitrate risk in double crop forages.

Many species that producers select as cover crops may be nitrate accumulators, meaning that special care must be taken while grazing cattle.

Warm season species such as corn, millet, sorghums, Sudan grass, sorghum/Sudan crosses and sunflowers, as well as cool season species such as brassicas and small cereal grasses including oats, cereal rye and wheat, are nitrate accumulators

Reducing risk

“There is a risk of high nitrates in many cover crop systems. It is always a good idea to test cover crops,” said Drewnoski.

Forages with zero to 1,100 parts per million (ppm) of nitrate-nitrogen are considered safe. Forages with a ppm of 1,100 to 2,100 are considered moderate risk, 2,100-3,400 ppm are considered high risk, and a ppm greater than 3,400 are considered severe risk.

Drewnoski cautioned producers that laboratories do vary in how they report nitrate levels. The two most common forms that tests will report in are nitrate-nitrogen and nitrate ion.

The ability to utilize nitrate-containing feeds depends on the concentration level, she said.

“There are some management practices that we can use to reduce risk when grazing moderate to moderately high nitrate cover crops,” continued Drewnoski. “For any samples that are severe risk, or greater than 3,400 ppm nitrate-nitrogen, the safest alternative is not to use them.”


Regardless of whether a producer is grazing high nitrate forages or not, Drewnoski strongly suggested making sure that cattle are full before putting them out on pastures.

“This is a good management practice regardless of the nitrate level because this slows down the intake of those cover crops initially to allow the rumen to get adjusted,” she said.

The key factor of filling cattle prior to transitioning them is controlling the rate of nitrate intake.

The conversion of nitrate to nitrite occurs much more rapidly than the conversion of nitrite to ammonia, explained Drewnoski.

“Nitrite is the toxic compound that can enter the blood, bind to hemoglobin and make it incapable of transporting oxygen, thus causing the animal to suffocate,” she said. “If we can have a slow intake of nitrate, we can then keep the flow of nitrite to ammonia at the same level as the flow of nitrate to nitrite.”

It is also advisable to feed higher nitrate feeds to lower-risk cattle. Open cows are the lowest risk, followed by growing calves.

“Pregnant cows are at greatest risk because the fetus is particularly susceptible to low oxygen, and abortion can result,” continued Drewnoski.


“Animals can safely adapt to higher nitrate levels, and this is because the bacteria that can utilize nitrite and convert it to ammonia can increase in number as nitrite availability increases in the rumen,” commented Drewnoski.

To adapt cattle, it is critical for producers to maintain a slow but steady increase in nitrite so bacterial numbers can increase at the same rate and not leave excess nitrite to enter the bloodstream, she explained.

“We suggest adapting cattle by starting grazing the lowest nitrate fields and then work up to the highest,” said Drewnoski.

Producers are also advised to graze animals lightly on higher nitrate forages to allow animals to selectively graze plant parts.

“Leaves are lower in nitrate concentration and cattle naturally select leaves,” she said. “Forcing the cattle to eat the stem, especially the lower stem, will increase nitrate intake.”


The final management strategy that Drewnoski suggested was supplementing cattle with grain while transitioning them to high nitrate forages.

She explained that grain supplementation is particularly useful when feeding high-nitrate lower-quality feeds.

“It is useful because we can supply extra energy to the rumen microbes to convert that nitrate to bacterial protein and minimize nitrate concentration,” she said.

Alternatively, producers may not see a benefit from supplementing grain while feeding higher quality forages.

“This may not be a useful strategy with high quality forages such as brassicas because the rumen available energy is already quite elevated,” she concluded.

Emilee Gibb is editor of Wyoming Livestock Roundup and can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..

Economists often complain that all animal scientists or range scientists want to talk about is economics. Well, I am turning the tables in this article. I am an economist, but I am talking about range management today. However, my co-author is a range scientist.

Range management can be a challenge in Wyoming, as Mother Nature can often be quite tricky to deal with. This summer, northern Wyoming is short on moisture and grass, while here in southwest Wyoming, we are having an amazing grass year.

Grazing plans are an important component of ranch management. An understanding of grazing fundamentals gives us a foundation on which to plan. Successful ranch managers strive for sustainable use of their forage resources. It is critical that the frequency, intensity and season of use that grazing occurs be thought out and managed for the health of the plants and livestock performance.

Frequency, the number of times a plant is grazed, can influence a plants ability to regrow. Plants grazed often may not be able to replace photosynthetic tissues during the growing season. Intensity, the amount of plant tissue removed, impacts plant health as well. However, if the grazing is done during dormant phases of plant growth, even high intensity grazing may have little impact. This timing, or season of use of the grazing, is the third component of the basics of grazing from a plant health perspective. Grazing plans should take care to ensure that some pastures are not subjected to too high of frequencies and/or intensities during critical plant growth stages.

Grazing plans should consider previous years’ use on pastures when planning for future years. Current years’ growing season precipitation is another critical planning tool for grazing plans. Ranch managers should monitor precipitation and available irrigation. Grazing plans should also include what do to in the case of drought. Drought plans may include partial destocking, purchase of additional feeds and pasture and increased attention to both plant health and livestock performance.

Most pastures on a ranch have had some previous livestock use. With records of what class, age and weight of animals grazed and for how long they were in the pasture, producers can estimate how much forage the livestock harvested and use that figure to estimate what the overall production of that pasture was.

Although the formulas for making these calculations have been around for quite some time, they have not been in a user-friendly online tool. With this in mind, we developed the latest tool on the Wyoming Ranch Tools Website at The tool is the “Stocking Rate” tool on the website and is really three to four calculators in one.

The first calculator on the page allows you to estimate total production per acre from past use records. The user enters in the number of head, average weight per head, days in pasture, acres in pasture and an estimate of the percent utilization. The calculator then provides the total animal unit months (AUMs) harvested, AUMs per acre, pounds consumed per acre and total production per acre.

Once you generate the total production per acre you can use the second calculator, which helps you estimate a stocking rate. The user enters the total production per acre, pasture utilization percentage, average weight per head, number of months the pasture is to be grazed and the acres in the pasture. The calculator then generates the forage availability for grazing, a one-month capacity given the weight of the animals and the number of animals that can be grazed for the intended grazing period.

The final calculator on the page helps to estimate a grazing season. Again, the user enters total production per acre, pasture utilization percentage, average weight per head, number of head and acres in the pasture. The calculator then provides the forage available for grazing and the months of grazing available for the specified animals.

A second tool is available under the clip-and-weigh tab. If you do not have past use information on a pasture, an alternate method for estimating production is the clip-and-weigh method. This tool walks you through the process of clipping and weighing random hoops to estimate production.

Animal performance should also be considered during planning for grazing. Nutrient levels vary over the growing season. During dormant stages some species nutrient levels may not meet the animal’s requirements. Ranch managers should become familiar with the nutrients in their forage species, how they vary over time, and what their livestock nutrient requirements are.

No matter what tool you use to estimate forage production and stocking rate, or if you use an online tool or the old pencil and paper method, it is important to include these estimates in a grazing plan. Even more important is to just take the time to think through and develop a written grazing plan. When we go through the process of writing a plan down, we often find things that we have previously overlooked or misjudged.

As livestock producers are planning their grazing systems for the year, University of Wyoming State Beef Extension Specialist Steve Paisley explains that many factors need to be considered for each season to optimize both plant and animal health.

The intensity that pastures are grazed and the length of time that animals are left in the pasture is partially dependent on the time of year, says Paisley.

He explains that typical springtime grazing programs rapidly move animals through small allotments.

“Usually, if we’re going to graze in the spring, we graze pretty moderate to heavy, so we try and graze smaller or more concentrated areas more heavily in the spring because that’s when the rapid growth hits,” Paisley says.

Alternatively, summer and fall grazing is normally done at a slower pace.

“Forage growth slows down, and we move cattle a little slower in the summer months,” continues Paisley.

Paisley explains that while every intensive grazing program is different, there are general recommendations for how long to allow animals to graze.

“If we’re in some kind of rapid movement or intensive grazing type of program, we’ll graze anywhere from three to seven days and then allow a minimum of 21 days recovery after that. That’s kind of a rule of thumb but every pasture size and number of cattle varies,” he says.

Plant health

From the perspective of plant health, intensive grazing in the spring is the most harmful, says Paisley.

“From the plant’s standpoint, probably the most detrimental time to graze grass is when they’re using up their root reserves to have a rapid growth phase,” he continues.

Repeatedly grazing the same pastures in the spring without a deferment period negatively impacts plant health. Alternatively, Paisley explains that rotational grazing programs aim to vary the time of year that pastures are utilized.

“If we graze the same location heavily during the same spring period every year, we’re going to negatively impact those grasses. The idea is we have the ability from a rotation standpoint to never graze the same pastures at the same time every year,” says Paisley.

As plants enter dormancy in the fall, intensively grazing the pasture will not have significant impacts on overall plant health.

“If we really want to protect or encourage grasses in a particular pasture, don’t graze it until after it goes dormant because then we’re going to allow it to respond and recover. Then we can graze it when it’s little or no impact on the plants,” he explains.

Stocking rate

“If we’re unfamiliar with the pasture, there are resources we can use to estimate and determine how long we should leave animals on a pasture,” says Paisley.

He explains that producers need to estimate total forage production in the pasture, then stock appropriately. Forage production will vary greatly depending on predominant grass types.

“In short-grass prairie, that is primarily buffalo grass and other short grasses, we’re going to stock those with fewer than we would a real rapid growing pasture, like a brome-type pasture. It depends on the location,” says Paisley.

The Natural Resource Conservation Service can be an excellent resource for recommendations on forage production and soil types for general areas around the state, says Paisley.

When determining stocking rates, Paisley explains that producers should estimate that livestock will remove 50 percent of the standing forage before moving to a new area.

“Try to work off of some guidelines to begin with. Know what an animal will eat each day and then try to back-calculate to what that is,” says Paisley.

Other considerations

As producers transition to different pastures for seasonal grazing, multiple other factors influence how heavily animals can be stocked.

Water availability is an important factor to be considered in grazing plans, says Paisley.

“We need to think about if there is enough water, especially if we’re concentrating a lot of animals in a small area,” he explains.

The presence of noxious weeds in pastures, particularly in the spring, should also be noted when deciding when to transition animals to new pastures.

“Other things that we typically think about in the spring time is that’s when we a lot of times will have our potentially noxious weeds, whether it’s lupines, larkspurs, death camas or any of those types of plants,” says Paisley.

He notes that intensive grazing programs can make noxious weeds become an even greater problem.

“Anytime we work with an intensive grazing type of a program, we can force animals to eat plants that they typically don’t eat,” continues Paisley.

Paisley stresses that not every pasture will be suitable for an intensive grazing program.

“We’ll have to look at that when we’re grazing to minimize the impacts of some of the plants that are in that pasture. We may have to wait until late summer or fall to graze it,” concludes Paisley.

Emilee Gibb is editor of Wyoming Livestock Roundup and can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..

Cheatgrass and lack of grazing are two factors that contribute to major wildfires in the West. If cheatgrass can be grazed in the fall, this reduces fire danger for the next year. Protein supplements can be used strategically to encourage cattle to use areas they might not otherwise graze. This enables cattle to use more of the pasture, as well as reduce fuel loads for wildfires.

Bill Wilber is a rancher in southeastern Oregon who lost 39 cattle on his range allotment during the Buzzard Complex Fire in July 2014, one of many fires in Oregon that year.

“This is a perfect example of the problem we’re trying to prevent. We participated in a research project with University of Nevada and Dr. Barry Perryman. His research study on reducing cheatgrass and medusahead with grazing has been quite successful,” says Wilber.

Studying the range

This study began in 2012, looking at the effects fall grazing could have on reducing fuel loads. Wilber moved 330 cows into a 14,000-acre pasture in early October 2012, and they grazed until Jan. 4, 2013 – more than 90 days of grazing on this cheatgrass-dominated range.

The study not only assessed the effects of fall grazing on cheatgrass, but also on the cattle.

“Prior to moving the cattle into this pasture, 20 percent of the cows were evaluated as to body condition score. They were re-evaluated when brought out of the pasture in January. There was improvement in body scores and weight gain,” says Wilber.

“In 2014, we again body scored 20 percent of the cows prior to going into the pasture and again when they were removed. The body condition scores were substantially higher after the cattle came out of the cheatgrass pasture,” he says.

This shows that they did very well on the dry cheatgrass, supplemented with protein.

Grazing successes

“This late season grazing has been very successful in three ways. The cows ate the buildup of fuel. It also saved us a substantial cost in hay since the cows were able to use cheatgrass during that period rather than being fed hay,” Wilber comments. “For this to work, however, they need a protein supplement to provide adequate protein to utilize the dry cheatgrass, and this makes it an excellent feed.”

“The third benefit is that the cattle actually maintained themselves very well and most of them gained weight,” he says.

Bureau of Land Management (BLM) cooperated in this project by allowing cattle to be out there in the late fall, which was later than their traditional use.

“They recognize that the buildup of fuel is a serious issue. The only way to remove it is by grazing,” he explains.

Fire impacts

“For this project, we put our cows into a very large pasture that had burned in 2007 because it had too much fuel load, and then after the fire it grew back even thicker to more cheatgrass and medusahead – a weed that is also a significant problem,” says Wilber.

“If it all burns up and the cheatgrass and medusahead come in thickly, that’s all we will have in that area, unless we can graze it off and give the perennial grasses a chance to come back,” he says.

“We had a tour afterward on this allotment and discovered perennial bunchgrass starting to re-emerge. The cattle had removed the competition. We can tip the balance back to perennials if we reduce the cheatgrass and medusahead. It’s a slow process, and we have to be patient,” says Wilber.

It will work, however, if cattle are allowed to graze these areas during fall and winter, he notes.

“We are hoping that this plan for grazing will continue on our allotment, but of course it will be up to the BLM to make that decision,” he adds. “It is successful enough, however, that there is precedence now being established.”

This is a good example to show what could be done on other ranges.

Working on rangelands

“The evidence is clear that BLM must do something about fuel buildups because of the horrendous fires we’ve been having,” says Wilber, adding that it costs BLM and taxpayers a lot of money to fight fires, destroying wildlife and their habitat – not including the grazing days and cattle lost in some of these fires.

“Rick Roy of BLM told me it cost $11 million in suppression costs on the Buzzard Complex Fire in which our cattle burned up. That’s a lot of money, especially when those fuels could be put to beneficial use as cattle feed instead of burning up,” he mentions.

“Ranchers are creating food and fiber and better wildlife habitat. Grazing benefits everyone, whereas fire does not,” he says.

There are several other areas in Oregon that are starting to use fall and winter grazing to control cheatgrass.

“The Roaring Springs Ranch at French Glen is also trying this, on private land. They are using smaller pastures, with a higher concentration of cattle. This is an exciting area of progress,” says Wilber. “Now all we have to do is change the minds of people who think we should have less cattle on rangelands.”

Other benefits

“Increased grazing is extremely beneficial for sage grouse. The environmental community believes that cattle are their worst enemy when in reality fire is their worst enemy,” Wilber comments. “Science shows that we need grazing and that cattle are a very positive part in our efforts to ensure sage grouse survival.”

He continues that ranchers need grazing to keep the plants in balance, with a healthy stand of perennials in a healthy ecosystem so catastrophic fires don’t destroy wildlife and their habitat.

“These ranges haven’t been overgrazed in our lifetime. Overgrazing took place 100 years ago. The move to reduce cattle is ongoing, however, and now the anti-grazing interests have overdone it,” says Wilber.

The land management agencies have taken too many cattle off, for too much of the year, according to Wilber, who says that the result is an overload of fuels that leads to catastrophic fires on a dry year.

“Reduction of fuels through cattle grazing is an appropriate management method. The research station at Burns, Ore. has verified the positive aspects of grazing,” he says. “This is a serious issue for the entire West.”

Wilber adds, “We are all suffering from horrendous fires that are the direct result of insufficient grazing. The stupidity of this is that in the end, everybody suffers.”

Heather Smith Thomas is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to This email address is being protected from spambots. You need JavaScript enabled to view it..