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Special care, planning should be taken when grazing annual forages

by Wyoming Livestock Roundup

University of Nebraska-Lincoln Extension Range and Forage Specialist Jerry Volesky explained annual forages can be an excellent grazing option for cattle producers, and certain considerations and approaches should be taken to optimize their usage.

“The annual forages are typically classified into the two main groups of cool season and warm season,” explained Volesky.

Cool season annuals include plants such as oats, spring triticale, spring barley, field peas and several other legumes.

“The cool season side also includes rye grasses, turnips, radishes and brassicas, as well as winter wheat, rye and triticale,” he continued.

Warm season annuals include both grazing and hay types of millet, sorghum/sudangrass hybrids, straight sorghum and sudangrass, as well as crabgrass, teff, forage corn and other legumes.

“Sometimes we’ll see the forage cocktails or cover crop mixtures have both cool and warm seasons within the same seed mix,” noted Volesky.


“Grazing is not as efficient as haying, and by this I mean that grazing interrupts the plant growth and that may reduce some of the potential growth of that plant,” said Volesky.

He also noted that there is a potential for trampling losses when grazing, as well.

When grazing, producers should take special care to begin grazing animals when the forage is at the appropriate stage of growth or height to promote plant health.

Volesky continued, “In the grazing system, simple rotations are beneficial. This certainly allows for an increase in the harvest efficiency.”

When using warm season annuals, he encouraged producers to use staggered plantings.

“By staggered plantings, I mean spacing out the planting dates across two or three different fields,” said Volesky. “It can be beneficial to avoid having the majority of that warm season annuals growing very fast and maturing too quickly before we get to graze it.”

It is also advisable to have some stocking flexibility and to have access to a nearby pasture in the event that cattle get ahead of what forage is growing.

With any annual, Volesky reminded producers to be mindful of nitrates and that some have the potential cause problems with prussic acid.

He also noted, “In the spring, on the lush cool seasons, grass tetany should be thought about.”

Grazing numbers

Cool season annuals and small grains should typically reach about six to eight inches in height before they’re grazed.

“For late summer-planted cool season annuals, we could allow more growth,” Volesky commented.

Warm season annuals should be approximately 15 to 20 inches high for sudangrass or pearl millet and 18 to 24 inches tall for sorghum/sudangrass hybrids.

When talking about carrying capacity, Volesky explained that an animal unit (AU) is equal to a 1,000-pound ruminant, which would consume 26 pounds of forage per day, and a cow/calf pair would be equal to 1.5 AUs.

“In terms of assuming grazing efficiency, we’ll typically assume about 50 percent grazing efficiency,” he continued.

When looking at early spring planted cool season annual forages and assuming a 2.5-ton-per-acre hay yield, Volesky said that the AUs grazed would be lower because of the decreased efficiency.

“If we were to graze that for one month, it would be 2.14 cow/calf pairs per acre, or if we grazed it for about 1.5 months, we would be able to stock it at about 1.42 cow/calf pairs per acre,” he noted.

When looking at warm season annuals averaging four tons per acre hay yield, if a producer decided to graze pairs for three months, the stocking rate would be 0.91 pairs per acre.


Volesky noted that there are other grazing options for annuals that producers can consider.

“With warm season annuals, we can stockpile them or leave them standing after they’ve completely frozen down and graze those later in the fall or early winter,” he said.

Windrowing is another option producers can consider after the first frost.

“Those forages could be windrowed and the windrows left in place for direct grazing,” continued Volesky.

Cool season annuals can be grazed down easily until the plants are completely frozen.

“It takes some pretty cold temperatures, in the 10 to 15 degree neighborhood, before cool season annuals completely stop growing for the year,” he commented.

For both types of annuals, strip grazing is another option. The portable fencing used could also be utilized in grazing windrows.

Emilee Gibb is editor of Wyoming Livestock Roundup and can be reached at

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