G2185

Utilizing Annual Forages with Limited Irrigation for Beef Cattle During and Following Drought

Recommendations for planting annual forages as alternatives to rangeland and pasture damaged by drought and excessive grazing.

Aaron L. Berger, Extension Educator
Tom L. Holman, Extension Educator
Jerry D. Volesky, Extension Range and Forage Specialist
Karla H. Jenkins, Cow-calf, Range Management Extension Specialist

Shelby oats, a cool season annual forage option with limited irrigation.
Shelby oats, a cool season annual forage option with limited irrigation.

Precipitation can be below average for much of western Nebraska for prolonged periods. Rangeland and pasture vegeta­tion in semi-arid environments, like central and western Nebraska, can be easily damaged by drought stress and/or excessive grazing. Consequently, even if soil moisture is not limited in the years following a drought, spring growth rate will be reduced and total annual forage production can be 20 to 50 percent below average. Therefore, stocking rates should be reduced 20 to 50 percent.

Growth of belowground plant parts in grasses is proportional to the amount of top growth each year. Drought-limited plant growth and/or excessive livestock grazing will reduce root growth, levels of stored energy, and formation of buds needed for future-year tillers. In addition, the remaining plant cover will be insufficient to keep rainwater from evaporating or running off the soil surface. The effects of drought will make it extremely difficult for most rangelands in the region to produce average levels of forage in the year following the drought even with above-average precipitation. Therefore, use of pastures in Nebraska should be delayed until June 1 for predominately cool season pastures or June 15 on rangeland predominated by warm season species. The greatest number of cow-days per acre will be obtained when pastures are not grazed until plants have completed most of their growth for the year. Using confinement feeding (see NebGuide G2099, Crop Residues or Low Quality Hay Combined with Byproducts as a Forage Substitute) and/or planted forages can provide alternatives so cattle can be kept off pastures and rangeland during the spring and well into the summer to allow unimpeded plant growth.

Continuation of drought, especially below average precipitation during April, May, and June, will eliminate opportunities for safe summer grazing on all pastures with limited plant cover.

Producers should consider limited irrigation and dryland forage crops as alternatives to pasture and rangeland requiring rest or deferred grazing.

Replacement Feed and Forage Alternatives Utilizing Limited Irrigation

Forage Production With Limited Irrigation Water (3-6 inches)

Plant spring small grains (oats, spring triticale, barley) March 15 to April 30.

Plant winter wheat, rye, or triticale Feb. 15 to March 15 (Also see NebGuide G2012, Forage Production with Limited Irrigation).

Plant warm season annuals (pearl millet, sorghum-sudan hybrids, sudangrass) from May 15 through July (see NebGuide G2172, Summer Annual Forages for Beef Cattle in Western Nebraska).

Plant cool season annuals (oats, spring triticale, barley, spring wheat, turnips, and other brassicas) from July 15 through August.

Average Irrigation Water Available (6-12 inches)

Plant spring cereal grains, spring triticale, oats, barley, and peas March 15 to April 30.

Plant winter wheat, rye, or triticale Feb. 15 to March 15.

Plant warm season annuals (pearl millet, foxtail millet, sorghum-sudan hybrids, sudangrass, corn) from June 1 to Aug. 1.

Plant cool season annuals (oats, spring triticale, barley, spring wheat, turnips, and other brassicas) from July 15 through Aug. 31.

Management Options to Capture Maximum Amount of Energy from Annual Forages

During drought conditions, producers will want to efficiently utilize available annual forage with cattle. The maximum amount of useable energy per acre from annual forages will be obtained when producers allow forage to reach the boot to soft dough stage of maturity before harvesting (Figure 1). The optimum point for harvesting varies with the annual forage used. Consider the following guidelines:

Obviously this window of opportunity for harvest is too narrow for the standing forage to effectively be utilized by direct grazing. Grazing crops at this stage of maturity would result in significant forage being wasted. However, swathing the crop at the optimum stage of maturity and then strip grazing using a temporary electric fence or an electric fence attached to a center pivot, which is moved periodically to limit access to windrows, can result in harvest efficiency of 85 percent or greater. For more information on management and use of this technique for forage harvesting, please see NebGuide G1616, Windrow Grazing.

 

Figure 1. Generalized relationship between forage and forage quality as affected by stage of maturity.
Figure 1. Generalized relationship between forage and forage quality as affected by stage of maturity.

 

Producers may find that direct, rotational grazing of annual forages at vegetative stages and then utilizing windrow grazing as forages mature will improve overall forage yield and utilization efficiency. Planting a sequence of forages that mature at different times (spring triticale, oats, sudangrass) is another way producers can have forage available for direct or windrow grazing throughout the spring and summer. Planning, along with efficient utilization can help maximize the amount of forage consumed from annual forage plantings.

When grazing lush immature small grain forages, be sure to provide cattle with high magnesium and calcium supplements starting a couple of months before turnout. This will help reduce changes of grass tetany. Cattle need to consume 3 to 4 ounces per day of a mineral containing 12 to 15 percent magnesium.

Nitrate and prussic acid poisoning are not generally a concern unless plants are stressed by drought or frost. Nitrates tend to be lower in forages harvested close to maturity, and raised with adequate moisture. Prussic acid poisoning can be avoided if stressed plants are not grazed for approximately seven days after a frost. For more information on managing nitrates in cattle feed see NebGuide G1779, Nitrates in Cattle Feeding.

This publication has been peer reviewed.

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Index: Range & Forage
Forages
Issued February 2013