Livestock

Cover crops add flexibility to grazing

While row-crop farmers expect cover crops to serve as a long-term payback from a short-term cost, livestock producers who graze cover crops see a more immediate return on investment. Planting cover crops produces high-quality forage and extends the grazing season into the winter, while also allowing pastures time to recover. The practice nour­ishes both cattle and the land with one crop.

Along with the benefits, however, there are some special consider­ations when using cover crops for grazing. As with any forage you feed, it’s important to know the quality to ensure you are meeting the herd’s nutritional requirements. This is particularly true when grazing cover crops. The quality will vary depending on the species, va­rieties and maturity. Forage quality parameters of most concern include crude protein, digestibility and fiber level as well as minerals.

Brassicas such as turnips and radishes often are incorporated into cover-crop mixes as a high-quality forage. They will have reported crude proteins of 14% to 27%, total digestible nutrients (TDN) of 70% to 80% and a lot of water—80% moisture is not uncommon. This combination can disrupt rumen function if you are not including higher-fiber forages such as grass hays, millet, sorghum or sudangrass. You may need to feed lower-quality hay, straw or other supplemental fiber to increase intake and maintain performance.

Some cover-crop species are potentially toxic to cattle. Be aware of these species, the conditions that increase the risk, and grazing man­agement practices that reduce the potential of cattle consuming toxic forage. The most common toxici­ties associated with cover crops are hydrocyanic acid (HCN), commonly known as prussic acid, and nitrates.

Sorghum, sudangrass and hybrids contain HCN in the leaves and stems. The concentration depends on the species, variety, maturity, plant injury or damage. The concen­trations of HCN decrease as the plant matures. Damage or injury to the plant from hail, insects, frost or harvest breaks cells and releases the toxins.

These grazing management strat­egies reduce the potential for HCN toxicity:

1. Delay grazing cattle until forage is 18 to 24 inches tall.

2. Avoid grazing regrowth under 12 inches.

3. Do not graze following hail or a light frost. Grazing 10 days after a killing frost is safe because the HCN dissipates quickly after the plant dies. When the plants are “lunch bag” brown, they are safe to graze.

Nitrates can accumulate in small-grain forages such as wheat, oats, rye, triticale and barley, or warm-season grasses such as sorghum, sudangrass and corn. Stressful growing conditions inhibit photosynthesis and increase the potential for nitrate accumulation. We typically associate nitrate accumulation with drought stress, but it also can occur during pro­longed periods of cool, cloudy weather. This is more likely in wetter, colder areas.

To reduce the risk of nitrate poisoning, provide cattle with a feed concentrate. This adds energy to the diet and dilutes the amount of nitrates eaten. Do not crowd ani­mals. High animal density increases the amount of plant stalks con­sumed. Nitrates accumulate in the lower plant stem. The picked-over forage in the bunk will have more stems, and thus more nitrates, than average.

A common complaint of grazing cover crops is forage waste. Forage waste can be reduced and harvest efficiency increased by dividing the field into cells based on stock­ing rate. Limiting the area cattle can access reduces feed waste and improves nutrient distribution. The most effective way to limit access is with temporary fencing. Fences can be set up prior to grazing or moving cattle into the next cell.

As you establish your grazing cells, be sure to consider access to water. This may limit the design of your grazing system, because many fields do not have developed water sources. An effective plan is to start grazing in the cell nearest the water source, and then move away from the water, allowing cattle to come back across the grazed areas to drink.

For more advice on growing, grazing and managing cover crops, talk with the livestock and agronomy experts at your MFA or AGChoice location.

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Prep pastures for stockpiling forages

Stockpiling got somewhat of bad name during the coronavirus pandemic as concerned consumers bought up toilet paper, sanitizing supplies and staple foods, leaving grocery store shelves bare for weeks.

But when it comes to forages for your livestock, stockpiling is a good thing. Stockpiled pastures can contribute significantly to late fall and winter feed needs for cows. And now’s the time to start preparing.

With stockpiling, perennial pastures are left to grow through the late summer and early fall rather than being harvested and stored. During this time days get shorter and temperatures get cooler, so high-quality, cool-season forages can accumulate, even after many days of growth. Missouri has an abundance of pastures planted in tall fescue, frequently argued to be the grass that stockpiles the best. Fescue maintains more active growth at lower temperatures than most other cool-season grasses, and the heavy waxy layer on the leaves makes the plant more resistant to frost damage.

Strip grazing stockpiled pasture results in better use of the forage. Use temporary electric wire to section off the field, allocating one to three days of feed allowance at a time for the herd. The Universi­ty of Missouri has found that this method increases grazing days by 40% over continuously grazing stockpiled forages.

To prepare pastures for stock­piling, graze the forage to a 3-inch residual and remove cattle. Make a nitrogen application, typically in August. The expected dry matter response to nitrogen is at least 10-fold. Ask your MFA agronomy specialist for specific recommenda­tions.

Stockpiled fescue holds its nu­tritive quality through the fall and winter. To cover the energy and protein requirements of gestating cows, stockpiled fescue should:

  • Provide greater than 3% of body weight as forage dry matter per head, per day.
  • Have average protein content greater than 12%.
  • Contain more than 55% total digestible nutrients.

At a minimum, cows in good flesh will need a mineral sup­plement. Feeding an ionophore improves the energy of the entire diet and is relatively painless to implement. It is always a good idea to send a forage sample to the lab to get an estimate of its nutritive value.

If the fescue in question is endo­phyte-infected, the alkaloids will decline the longer the fescue stands in the pasture. Higher nitrogen applications to infected-fescue pastures tend to increase the level of toxic alkaloids. Nontoxic fescues respond to additional fertility and don’t produce the detrimental alka­loids. I typically see 2,000 to 3,000 pounds of dry matter per acre with stockpiled fescue. To reach those higher yields, you need good condi­tions and good fertility.

If you’re far enough south, ber­mudagrass also stockpiles well, but you should use an improved culti­var for best results. Hybrid bermu­dagrass varieties tend to work better in stockpile because of their higher yield potential compared to com­mon bermudagrass. Ask your MFA agronomy specialist for site-specific recommendations.

A warm-season forage, bermu­dagrass dislikes cooler weather. It grows best between 85 and 95 degrees, and quality declines sharp­ly if temperatures drop below 60 degrees at night. If there is an early frost, it is done for the year. Howev­er, if fall temperatures are relatively warm, the dry matter yield can be impressive.

Bermuda is a heavy feeder, so hefty applications of fertility are required. As with fescue, graze the pasture to a 3-inch residual in early August. Remove cattle, and then make a fertility application at the start of stockpiling. Strip grazing also works best with bermudagrass.

No matter the forage you plan to stockpile, timing is a key strategy for success. Manage so that you give yourself as many growing days as possible for stockpile growth to occur before the first frosts.

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Protect health of bred cows this summer

Getting cows and heifers bred is only part of the challenge in beef and dairy production. Keeping them bred also requires careful management, especially during the summer. High heat index (com­bined temperature and humidity) is a common environmental factor in early pregnancy loss and can increase the risk well into the second and even third trimesters. Heat stress can also have a long-term effect on egg quality and, thus, embryo quality.

In July 2018, after a northern Missouri beef herd owner saw his bull breeding cows that were known to be pregnant from an earlier pregnancy check, University of Missouri Veterinarian Dr. Scott Poock took his ultrasound device to the field for rechecks of pregnan­cies. Overall, he found an average of 20% open in the herds he checked. The few exceptions were bred early in April prior to May heat. He also received reports of beef cows showing heats at 30 to 50 days after timed artificial insemination. These cows likely conceived but then lost their embryo.

That same summer, Poock found up to 25% loss of pregnancies after early diagnosis (30-32 days of gesta­tion) at MU’s Foremost Dairy. He also found dead embryos from AI breed­ing from mid-May through June.

Heat-related pregnancy losses are caused by several factors, includ­ing increased internal temperature of the cow. The early embryo is sensitive to body temperatures above normal. At six to eight days, the embryo becomes heat tolerant. Early heat stress potentially leads to embryo loss within the first week after breeding; these cows come back into heat on schedule.

High temperatures also disrupt ovarian and uterine functions. Egg quality declines with oocytes being compromised. Fertilization occurs, but the fertilized egg does not develop normally. The embryo dies later. Such cows return to heat at strange intervals.

And, in some cases, it may not be the cow’s fault. Heat stress affects bulls, too. It can decrease sperm quality, which leads to fewer preg­nancies.

Open cows or heifers are ex­pensive. While there is a cost to pregnancy diagnosis, it is a valuable tool for managing or marketing cat­tle. Obtaining the highest value for every female is critical. Selling open cows or heifers prior to the seasonal cull cow market price decline in August and September has huge economic benefit. If forage availabil­ity is below normal, selling known open cows or heifers extends forage resources and reduces feed costs.

Consider the different pregnancy diagnostic options:

  • Rectal palpation provides im­mediate results, allowing cows to be chute sorted at 35 days post-breeding. It requires signif­icant experience and can cause early embryonic loss of 1-3%.
  • Ultrasound is most expensive and requires a technician but can be performed at 28 days post-breeding. Depending on when it’s used, ultrasound is the most informative tool avail­able. Results are immediate and allow you to identify the calf’s age and sex.
  • Blood testing is the most inexpensive and least invasive method, with accurate results at 30 days post-breeding. Results are typically delayed two to four days, no calf information is available, and cows should be 90 days post-calving to avoid false positives.

The type of female being evaluat­ed is important in your decision on what method to use. Since heifers don’t have a calf by their side, blood test and quick marketing is an op­tion for those that aren’t pregnant. Conversely, for cow-calf pairs not being weaned early, palpation at a later date works.

For cows and heifers that are found to be pregnant, an early diagnosis allows you to make timely decisions to minimize heat stress and help protect the unborn calves through the summer. Heat abate­ment strategies such as ensuring ad­equate water and shade are critical. Watering stations need to be located conveniently to allow multiple cows access and keep up with hydration demands. Shade can be provided by trees, buildings, or shade struc­tures. Evaporative cooling systems also can be used in barns to help beat the heat. Beyond reproductive benefits, minimizing heat stress also improves overall cow health, production and well-being during the summer season.

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Heat can harm hay quality

Spontaneous heating in hay, generally caused by too much moisture in the plant at the time of baling, costs livestock producers in terms of dry matter losses and forage quality. Hay that has heated during storage will often appear brown or caramelized in color. Live­stock will often like the flavor, but nutrients have been lost due to the excessive heating during storage.

With small rectangular bales, those weighing less than 100 pounds, there is a positive linear relationship between moisture content at the time of baling and heating. The wetter the hay, the greater the chance of heating.

These days, many producers use larger round or square bales. The U.S. Dairy Forage Research Center conducted several studies to deter­mine if bale moisture and diameter (3-, 4-, or 5-foot bales) had an impact on spontaneous heating. Re­searchers also measured the amount of dry matter lost and the digestibil­ity of the damaged forages.

Just like small rectangular bales, the study found that heating in­creased with the moisture content for each bale diameter. But as size increases, the larger bales are more likely to exhibit spontaneous heating at relatively low moisture contents, less than 20%, and to ac­cumulate more heating degree days during storage. Similar to “growing degree days” used by agronomists, the heating degree day measure­ment aggregates the internal bale temperature over time. Larger bales also pose an increased risk of spon­taneous combustion.

The increase in heating degree days with larger bales is due to two factors: Larger and/or denser bales contain more dry matter, and larger bales have less surface area per unit of forage dry matter, which impedes dissipation of heat and water.

Heat damage in forages is often viewed in binary terms, meaning that the forage is either damaged or not. In reality, the effects of heating on forage quality are better de­scribed as a continuum. Damaged protein is not necessarily the most negative consequence of spon­taneous heating. Concentrations of neutral detergent fiber (NDF) increased by as much as 11 percent­age units as a result of spontaneous heating. NDF measures structural carbohydrates representing the fibrous bulk of the forage. As NDF content of a feed increases, dry matter intake will decrease.

It’s important to note that NDF is not really generated during the heating process. Increases in NDF concentrations occur because cell solubles, specifically sugars, are ox­idized first during microbial respi­ration. Therefore, the concentration of fiber components such as NDF and acid detergent fiber (ADF) in­crease because the concentration of cell solubles decreases. This is par­ticularly important because sugars and other cell solubles are essen­tially 100% digestible, while fiber components are not. As a result, spontaneous heating decreases the forage’s energy density, expressed as total digestible nutrients.

Traditionally, the threshold moisture level for acceptable storage for small rectangular bales has been about 20%. To limit heating, this must be reduced to 16-18% for large round or square bales. For legume hays, these issues create a difficult management situation because lower moisture levels lead to greater leaf shatter and a drop in forage quality. It may not be possi­ble to completely eliminate heating and optimize recovery of leaves in large legume hay bales without preservatives or plastic wrap to eliminate oxygen.

In storage, air movement around bales will help to dissipate both water and heat. Producers storing bales under roof should consider managing moisture at baling even more conservatively.

If heat damage is suspected, a feed nutrient analysis is recom­mended before diet formulation to determine the quality of the forage. Tests for heat-damaged protein in forages are expressed in many ways by commercial forage-testing laboratories, but the best definition is acid detergent fiber crude protein (ADF-CP). All forages contain some ADF-CP, which is largely indigest­ible by ruminants. Benchmarks suggest that if this fraction is less than 10% of the total forage crude protein, then minimal heat damage has occurred during storage.

We are often at the mercy of the weather when putting up hay under ideal moisture conditions. Monitor­ing hay moisture during baling and temperature at storage time is essen­tial to having high-quality forages available for feeding livestock and minimizing storage losses.

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Cocklebur can be a pasture peril

If you’ve ever had to disentangle spiny cockleburs from a dog’s fur, you know just how problematic these prickly little pests can be. But inconvenience isn’t the worst of the problems. The cocklebur plant itself is poisonous to livestock.

A coarse, herbaceous annual weed, cockleburs start growing in the spring, mainly along fence­rows, ditches and low-lying areas of pastures. The cocklebur is found throughout the world, but here in the United States, Xanthium stru­marium is the species involved in livestock toxicity. Cocklebur poison­ings are also common in Australia and South Africa.

Toxicity to animals can occur at different times of the year, but newly emerged plants are the big­gest concern. The toxic principle, carboxyatractyloside, is present in the seeds and young seedlings, especially during the two-leaf stage of growth. The toxin concentration drops rapidly when the first true leaves appear.

Early spring is a problem time in pastures, but animals can be poisoned later in the year when mature seeds drop and start to grow. Hogs are particularly sus­ceptible to cocklebur poisoning, but the seedlings will also poison chickens, sheep, cattle and horses. Usually animals don’t eat the seeds for obvious reasons, but problems can also occur when cattle are fed whole cottonseed or hay contaminated with cocklebur. Seedlings are toxic even when dead and dry.

Signs of toxicity in livestock include de­pression, reluctance to move, a hunched pos­ture, nausea, vomiting, weakness, prostration and labored breathing; they will also show an abnormal posture with the back extremely arched due to muscle spasms. You may see leg paddling and convul­sions when lying down. Coma and death are possible. Other indi­cations of cocklebur toxicity are hypoglyce­mia, increased vascular permeability and gastro­intestinal tract irritation.

The minimum lethal dose of cocklebur seeds is about 0.3% of body weight; for rough figuring, that is 10-20% of cattle feed intake. Thirty years ago, the Journal of Veterinary Diagnostic Investigation reported an incidence of cockle­bur toxicosis in cattle. The cattle were fed hay contaminated with mature cocklebur plants. Clinical signs ranged from death to hy­perexcitability, blindness, tense musculature, spastic gaits, lying down and convulsions. Research­ers reported 100-200 ppm of carboxyatractyloside in the rumen contents.

Good pasture management can greatly reduce the risk of cocklebur poisoning. Clipping pastures before seeds mature can help eliminate the spread of this weed. Many herbicides are labeled for cocklebur control, so a solid weed-control program is also effective. Rotation­al grazing will allow your pasture grass to thrive and discourage the growth of weeds and toxic plants. In addition, ensuring your animals have a quality feed and source of hay free of cocklebur contamina­tion will help you avoid potential problems.

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