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Grazing Cover Crops


By Pete Fandel and Dean Oswald

Successful, sustainable and profitable livestock operations maximize the use of forage crops by extending the grazing season as long as the weather permits. Operations with the highest grazing days usually have a lower purchased feed cost and more profit at the end of the year.  Most livestock are grazing animals, and will do a great job of harvesting forage even in the snow. Greater grazing days also reduce energy and equipment use on the farm as animals spread their own manure when on pasture.

To achieve that goal you will likely need to combine Management Intensive Grazing (MIG), strip grazing, and cover crops into your farming operation to extend the grazing season. MIG is a size neutral technology that works well in small or large operations. MIG is grazing system that utilizes several smaller paddocks (pastures) instead of a fewer larger paddocks. The reason for having more, smaller paddocks is that your paddocks can be harvested more efficiently by livestock if you treat them like an alfalfa field instead of a typical continuously grazed pasture.

In an alfalfa field you allow the alfalfa get to beginning bloom stage, cut the hay, and basically bale it 3 days later. The entire production of the field is harvested in 3 days, and the field gets to “rest”/regrow for to next 28-32 days before it is harvested again.

Similarly, if paddocks were managed with a 3-6 day grazing cycle they would be able to produce more tons of forage per acre. The paddocks would have higher stocking rates than when the livestock are out every day eating the new top growth off the plant, and never allowing the plant a “resting”/regrowth period.

To achieve this scenario, ideally you would need at least 6-12 paddocks. The animals are moved into a paddock when the forage is 8 – 12 inches high and if it was sized correctly, they should have enough forage for a 3 to 6 day grazing cycle. Paddocks do not need to have the same acreage but should be designed to have similar forage production for similar grazing intervals. Animals are removed when 3-4 inches of forage residue remains in the paddock. This is critical for quick forage regrowth and pasture health. The goal for the pasture would be to provide a thirty day rest period for paddocks containing legumes or at least 21 days for grass pastures. Adequate rest period and short grazing intervals make managed grazing work. This will increase pasture productivity and improve harvest efficiency.  It is helpful to have an extra sacrifice paddock that the livestock can be moved to when the weather is wet/muddy so that they are not trampling or ruining one of the good paddocks.

Producers should consider many different species to maximize the grazing season. Cool season perennial grasses work well in the spring and fall when the weather is cool. Grass and legume mixes help to reduce the need for supplemental nitrogen application. Warm season perennial plants will do better in the hottest part of the summer when cool season forages tend to go dormant.  Other forages can work well into the winter when most of our common species go dormant for the winter. This is where we can start thinking about cover crops as a forage source during the late fall through spring time frame.

There are many species of plants that can be used or added to a grazing operation to enhance the productivity of the forages, extend the grazing season, or provide emergency forage when your operation is short on feed.

Pasture Improvement

The easiest thing you can do to improve your pastures is diversifying your plant species. If your pasture is predominantly grass, you can add legumes to increase the protein value of the forage and help add nitrogen to the soil for the grasses. Many of the clovers can easily be added to an existing pasture by frost seeding them into the pasture during the early spring (late February-mid March) depending on the weather that spring. Your goal is to get the clover spread just before the daytime temperatures are getting above freezing, but the night temperatures drop below freezing. This will allow the natural frost cycle to work the seed into the soil and allow for good seed to soil contact. Then as the temperatures continue to climb, the clovers will germinate and get established before the grasses start their spring regrowth. The seeding rate will depend on which clover species you select and how diversified your plant species are in your pasture. Keep in mind legumes need a pH between 6.3-7.0 to maximize longevity in the pasture stand, so if you plan to add legumes, take soil samples at least a year in advance so that you will have the opportunity (if needed) to add lime and correct a possible low pH at least 6 months before you seed the legumes.

The next easiest thing you can do is to try and extend your grazing season into the late fall or winter. Many producers will pasture their corn stalks after harvest, but you can increase the protein content and grazing efficiency in those fields by adding other species and strip grazing the field rather than turning the livestock out into the entire field at once. Several species of plants can be successfully aerial seeded into the standing corn field in late August or early September. They will germinate and start growing as the corn plants are maturing. When the corn is harvested, these plants will respond to the increasing sunlight and residual fertilizer and grow well into the late fall or early winter. This mix of corn residue and high quality young plants provides excellent forage for your livestock.  There are many species of plants that you could use, but some of the most widely used for this purpose are annual rye, cereal rye, and turnips. However, if you want to get the most grazing efficiency from fields like this, you will need to strip-graze the field. To accomplish this, use an internal, easily moved fence to make sure the animals consume a larger percentage of the available forage before they are allowed to access more of the field. If animals are allowed to graze the entire field, they will tend to only eat the most desirable forage and waste the rest.

Annual Forages

There are many other species of plants that can be utilized in a grazing system. Annual forages are often thought of as supplemental or emergency crops. Annuals can play and important niche role in a total forage system. Supplemental forages are needed when winter injury impairs forage crop stands, drought decreases yields, or extended grazing seasons are needed. Reasons for considering annual forages might include:

1) When transitioning from one forage to another to improve a pasture.

2) As an intervening crop between an old alfalfa stand and a new alfalfa seeding to eliminate concerns of autotoxicity.

3) As a follow up forage crop to wheat or a winter killed or poor hay stand after the first cutting is removed.

4) In a lot that is not utilized during the summer.

5) In areas damaged by winter hay feeding or high concentrations of livestock.

6) Silage fields or row crops as a winter cover crop for erosion control and nutrient recycling, and extending the grazing season into the fall & winter.

Annual forages may require special considerations for the livestock producer. Growers should consider seeding rates and seed costs of annuals as a replacement for stored feed. Strip grazing annuals, cover crops and corn crop residues will reduce forage waste, maintain higher quality forage and increase harvest efficiency. A higher level of animal management may be required.

Animal Health Issues

Some species of cover crops have the potential for livestock feeding cautions or health concerns which can be avoided with good management. This section is provided not to reduce the use and acceptance of cover crops for livestock. Quite the opposite! We heartily encourage the use of cover crops for extended grazing, improved forage quality in the fall and winter, and increased sustainability and profitability in the livestock industry. Be aware that the potential health concerns exist, but problems can be avoided through proper management.

Bloat can be an issue with most legume species. Having animals full when changing pastures; changing paddocks in the afternoon when forage is dry; grass-legume pastures; and managed grazing helps to reduce bloat. Feeding poloxalene blocks prior to turn out affectively eliminates bloat by adding a de-foaming agent to the rumen.

Prussic-acid poisoning occurs in sudangrass and hybrids.  Toxic levels of prussic acid occur most commonly in vegetative growth or after a killing frost or drought. Horses grazing sorghums can contract cystitis a urinary tract problem. 

Nitrate poisoning usually occurs when high rates of manure or nitrogen fertilizer are used in one application and then a drought or sudden weather changes occur. Higher nitrate levels are found in the lower stems. Nitrates harvested in hay do not dissipate as it cures, so problems can occur when the hay is fed.

Grass tetany occurs when livestock are grazing lush pasture in the spring or grazing cereal crops spring or fall. Magnesium oxide should be supplemented in a free-choice salt/mineral mix to avoid this problem.

Brassica crops can cause animal health disorders if not grazed properly.  This includes the turnip, radish, rape, kale, etc. The main disorders are bloat, atypical pneumonia, nitrate poisoning, hemolytic anemia (mainly kale), hypothyroidism, and polioencephalomalacia. These disorders can be prevented by good grazing management practices:

Introduce grazing animals to brassica pastures slowly (over 3-4 days).  Avoid abrupt dietary changes from dry summer pastures to lush brassica pastures.  Don’t turn hungry animals that are not adapted to brassicas into a brassica pasture.  The forage quality is so high that it should be considered similar to concentrate feeds and precautions taken accordingly.

Brassica crops should not constitute more than 65-75% of the animal diet. Supplement with dry hay or stockpiled grasses while grazing brassicas.  No-tilling into grass sod or planting with cereal grasses can help to reduce potential grazing problems by increasing fiber in the diet. Animals prefer fresh forage material and may not consume dry hay readily. That is why it is best to plant grasses with brassicas.

Cover crop feed value

Cover crops can improve existing crop residues to easily meet the nutritional needs of livestock. They provide emergency or supplemental forage supplies for grazing animals. Fresh forages can add protein, energy and other essential nutrients to the animal diet. Like other forages, cover crop maturity affects forage quality more than any other factor. Producers must then optimize both quality and yield. As plants mature they will be lower in feed nutrient quality, protein reduction, increased fiber with reduced digestibility and relative feed value. 

Annual ryegrass can range from 10-20% CP, and 90-190 relative feed value with proper fertility and harvest management. Relative feed value of 100 equals the feed value of full bloom alfalfa hay. The crude protein and energy level make annual ryegrass a valuable forage. TDN 55-60% and DE 2.4-2.65 Mcal/kg

Cereal grains used as forage can be comparable to other cool season grasses. Cereals do not vary much in quality fresh forage 20-25% CP, hay 15-16% CP with 42-67% digestibility depending upon stage of growth. Relative feed values ranged from 140 to 160. Toward maturity relative feed values will be reduced to 85-90.

Brassica crops which include turnips, radishes, rape, kale and other hybrids have shown that the leaves and stems have 17 to 25% crude protein and 65 to 80% digestibility.  The roots have 10 to 14% crude protein and 80 to 85% digestibility. Remember to plant with a grass fiber source. Relative feed values of brassicas vary from 150-250.

The sudan and sorghum family: sudangrass, hybrid sorghum-sudan 12-14% CP and relative feed values of 90-110. Brown mid-rib varieties have increased digestibility because of lower lignin levels. Care should be taken after a frost to prevent prussic acid poisoning.

The millets: Japanese, foxtail, and pearl exhibit CP levels of 12-14%. Relative feed values for the millet family run around 100 or slightly above.

Legumes: Crimson clover has a CP of 17% and TDN of 59%. Red clover CP is 15% and has a digestibility of 61%. Sweet clover is similar with CP of 15% and digestibility of 56%. Crimson clover has 16% CP and 59% TDN.  Hairy vetch is also in the area of 16% CP and 55-60% TDN. Finally, the field pea is slightly higher in CP with 20% and 70% TDN. Legumes can add quality by increasing CP and providing nitrogen to companion grasses.

Crop producers as well as livestock producers need to consider and adopt cover crops into their farm management system. Depending on what species you plant, cover crops can have many positive benefits to your farming operation. Some of these include: building up your soils organic matter, tying up residual fertilizer/nutrients, improving soil structure, improving water infiltration rates, increasing microbial populations, promoting greater rooting depth, and reducing erosion. All of these factors will help increase the yield potential of your traditional crops. In fact, most cover crop research is showing a 3-5 bushel per acre yield increase on soybeans and a 15-30 bushel per acre increase in corn yields.  In addition to the increased yields, cover crops can achieve higher water quality standards and reduce soil nutrient losses. Through this improved soil and water stewardship, we can progress to greater sustainability and profitability, and hopefully reduce the chances of increasing regulation in our farming enterprise.

View the cover crops and livestock info chart.