Annual Forages Offer Grazing Option

Grazing Warm-Season Annual Forages Gives Cattle Producers a Fast-Growing Option

Russ Quinn
By  Russ Quinn , DTN Staff Reporter
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Attendees of the 2023 University of Nebraska Extension Pasture Walk examine warm-season annual forage grazing. (DTN photo by Russ Quinn)

MEAD, Neb. (DTN) -- Warm-season annual forage grazing offers cattle producers a quick-growing option for those who are short on traditional perennial grass pastures. While these forages can supplement grazing plans, producers should be aware of the management differences when grazing cool-season pasture versus running livestock on warm-season forages.


University of Nebraska Extension hosted a pasture walk during the morning of Aug. 23 at a field at the Eastern Nebraska Research, Extension and Education Center south of Mead, Nebraska. University of Nebraska Extension Beef Systems Specialist Mary Drewnoski led the field tour and informed field day attendees of their successes and failures grazing warm-season annual forage this growing season.

Grazing on warm-season annual forages requires a different mindset for livestock producers, according to Drewnoski. Grazing cool-season forages requires some care and caution, while warm-season forages must be grazed immediately when it's time.

"They are two totally different mindsets, which is hard for some to do," Drewnoski said.

One of the major challenges with warm-season annuals is to keep the forage immature and not allow the forage to mature before grazing can occur -- otherwise, the crop gets too advanced or decreases the forage quality considerably.

Half a field at the research center was planted this spring to a sudangrass/sunn hemp mixture, and the other half of the field with sudangrass monoculture. Both stocker cattle and cow-calf pairs would then graze the forage, which was divided up into smaller paddocks, for three to four days at a time.

Data shows that pre-graze, there was an average of 1,850 pounds of forage per acre for the sudangrass/sunn hemp mixture. There was 1,874 lbs./acre for the sudangrass monoculture.


Drewnoski said cattle must be turned out onto the warm-season annuals at 18 inches to 2 feet of growth, which is generally about 45 days after planting. Waiting to graze when the crop is too mature will lower quality but will also lead to much less regrowth because of waiting too long to graze.

"You almost have to graze faster than you think," she said.

Drewnoski said one of the interesting things they learned this summer with their research is how fast the forages' regrowth is affected by when grazing is begun and the stocking rate.

Daren Redfearn, University of Nebraska Extension forage crop residue specialist, said the earliest-grazed paddocks featured plants with more tillering. These tillers emerge from the plant after being grazed and are key to quick regrowth and continued grazing, he noted.

These plants are meant to be grazed to roughly 8 inches of growth and then sit for some regrowth, Redfearn said.

"As little as three days after the cattle are removed, regrowth can be seen," Redfearn said.

Initial stocking rates were 2.3 stockers per acre and 1.2 pairs per acre (with bull). The stocking rates were lowered as the growing season progressed to 1.5 stockers per acre and 1.1 pairs per acre (with bull).

The advantage of fast growth can also be a disadvantage, as cattle need to graze when the forage reaches a certain height. Having enough cattle to be able to graze down the forage is required.


Another challenge with grazing warm-season annual forages like sudangrass is how to handle the end-of-the-season grazing with frost. The forage releases prussic acid at a killing frost, which can kill livestock.

Drewnoski said that ideally, producers should pull the cattle off the forage before the first frost. They should keep the cattle off the forage for at least seven days after the first killing frost, which occurs when the temperature is at 28 degrees Fahrenheit or lower.

The cattle can return to grazing after that time to the end of the grazing season, Drewnoski said.

"Some of our producers will plant pearl millet, as that crop does not have any issue with prussic acid," Drewnoski said. "Some will even plant both crops."

Redfearn said the seeding rate for warm-season annual forages is 20 to 30 lbs./acre. In the field shown during the walk, it was seeded on May 29 after cereal rye was terminated. Sudangrass was seeded at 26 lbs./acre, while the sudangrass mixed with sunn hemp was seeded at 29 lbs./acre.

No nitrogen was added to the field, but 40 lbs./acre residual nitrogen was present. Drewnoski said student research assistants and she debated whether the field would have benefited from additional nitrogen.

Other sources for information on grazing or establishing warm-season annual forage pasture:





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Russ Quinn