6 Cautions When Grazing Cover Crops

Grazing cover crops can be a cost-effective way to achieve multiple productions goals.  Cover crops can provide ground cover to prevent erosion, improve soil health over time, and provide nutrition to beef cattle.  However, cover crops are not a fool proof feed.  Turning cattle out onto cover crops to graze without proper feed tests can lead to a wreak due to improper management.  Recently, I had a producer lose 12 head of growing cattle to polioencephalomalacia, a neurological disease in cattle consuming too much sulfur.  After the incident, that producer wanted to test his cover crops to ensure he did not experience another tragic loss.  My advice, is to test cover crops before grazing for protein, energy value, minerals, nitrates, and under some circumstances, prussic acid to ensure proper management and prevent undue losses. These are the 6 cautions to consider when grazing cover crops:

  1. Nitrates

Cover crop mixes include several plant species known to accumulate nitrates for example: brassicas, such as turnips and radishes, or small grain plants, such as oats, millet, or grain sorghums. When cattle consume high nitrate feeds, the microbes in the rumen convert that nitrate to nitrite.  The nitrite is then in the gas, which the cattle belch and then inhale.  The nitrite then binds to the blood hemoglobin preventing oxygen from binding.  At levels between 1,400 – 2100 ppm NO3-N this can cause spontaneous abortions with no warning signs or symptoms.  At levels between 2,100 – 4,000 ppm NO3-N sudden death may occur and therefore, animals grazing cover crops should be slowly acclimated to consumption of nitrates and offered a low nitrate roughage to fill up on first.  Never allow hungry cattle onto a high nitrate field.  Nitrate levels above 4,000 ppm NO3-N should not be grazed as sudden death will likely occur.

  1. High sulfur

The toxic level of sulfur in a cattle diet is 0.40 ppm on a dry basis.  Brassicas are sulfur accumulators, that occasionally test above the maximum tolerable level, and are often included in cover crop grazing mixes.  When sulfur intake is above the tolerable level, thiamin metabolism is impaired in a condition known as polioencephalomalacia (PEM). Head pressing, blindness, and muscle tremors are all clinical symptoms of PEM which, untreated, results in death.

  1. Low magnesium

Grass tetany is a condition commonly associated with lush spring pastures.  These pastures are known for having low magnesium due to rapid growth conditions. Cover crops also tend to have low magnesium.   The magnesium requirement for a beef cow is 0.2% of the diet at peak lactation and 0.1% of the diet for growing cattle.  When cover crops contain less magnesium than is required, a magnesium deficiency can develop resulting in grass tetany.  The signs of grass tetany are cattle stop grazing, become overly alert, and appear uncomfortable, they will then begin to stagger until they finally lie down with their head pulled back into a “star gazing position”.  Untreated, this condition will result in death.  To prevent the development of a magnesium deficiency, many producers grazing cover crops feed a mineral between 8-12% magnesium to be consumed at a rate of 2.5-4oz per head per day.

  1. Prussic acid

In cover crop mixes there are species of plants which accumulate hydrogen cyanide, a poisonous gas commonly known as prussic acid, in their leaves under stressful growing conditions.  These plants include sorghum grasses, sudan grasses, and flax.  Stressful growing conditions includes drought or frost.  Plants grown in drought conditions should be tested for prussic acid prior to grazing because consumption of high levels of the gas is sudden death.  Contrarily, frost typically breaks cell walls allowing the release of the gas and therefore should be safe to graze after 4 days.  Regrowth after a frost however, should be tested prior to grazing because the plant is stressed from the previous frost, but the cell walls have not been broken to allow the gas to escape.

  1. Bloat

A frothy bloat is often attributed to legumes or high protein grasses.  Cover crop mixes high in legumes such as clover, beans, or cowpeas may result in some animals over indulging in the legumes resulting in frothy bloat issues.  These legume plants are high in soluble protein and sugars which allows the microbes to ferment and grow at a rapid rate resulting in a high rate of gaseous by-product accumulation.

  1. Choke

Brassicas such as radishes and turnips may be pulled from the ground to be consumed by cattle grazing cover crops.  If they are swallowed without proper mastication the animal may choke on the large root.  This is typically more of a problem for young cattle who are inexperienced in grazing brassicas.

Overall, grazing cover crops can be a great way to provide nutrients to cattle, prevent soil erosion and improve soil health.  However, the producer should be aware of the risks they are assuming feeding these diverse forages.  Testing for nitrates, minerals, and potentially prussic acid is highly recommended to avoid unnecessary losses due to grazing cover crops.

 

7 Concepts on Hay Analysis for Horses with Metabolic Conditions

Over the past year, when I receive phone calls from equine enthusiasts, they all seem to have the same question. What do I need to analyze my hay for a horse that has been diagnosed with Equine Metabolic Syndrome, Cushing’s Disease, Equine Diabetes or is prone to Laminitis?

While the pathology and causes of each of these disorders may be very different, they all can be managed through diet. Each of these conditions requires the horse to consume a low, simple carbohydrate diet. This means feeding no cereal grains, which are high in starches, but instead feeding a high fiber, forage based diet. I typically recommend that these clients run an NIR plus TSI plus Starch. When choosing a hay or analyzing pasture grass for suitability to feed horses with metabolic conditions, there are 7 key concepts to examine.

1. Protein

When determining a forage to feed, it is important to realize that without grain supplementation, it will be important to meet the horses protein requirements. Most horses at maintenance require 10% crude protein on a dry basis. Growing, breeding, and working or performing horses have increased protein requirements depending on their physiological state and physical activity level.

2. Acid Detergent Fiber (ADF)

The ADF is an indicator of the digestible energy available in a feed. Most horses at maintenance require between 37-40% ADF on a dry basis. Higher fiber percentages in a forage indicates that there is more structural carbohydrates in the feed and therefore less water soluble carbohydrates such as sugars and starches, which should be avoided when managing a metabolic condition.

3. Neutral Detergent Fiber (NDF)

Similar to ADF, increased NDF also indicates that more carbohydrates have been converted from water soluble carbohydrates to structural carbohydrates, therefore forages with higher NDF tend to be better for managing a horse with a metabolic syndrome. Most horses at maintenance require between 50-65% NDF on a dry basis. The NDF is an indicator of dry matter intake and palatability, as NDF increases the horse will consume less of that feed, so avoid a hay with an NDF much higher than 65%.

4. Relative Feed Value (RFV)

The RFV is a calculated index based on the ADF and NDF. A good hay to maintain a horses condition would have a RFV between 83-112. Typically, grass hays and grass forages are going to meet the RFV recommendations for horses with metabolic conditions as opposed to commonly fed legumes such as alfalfa hay.

5. Non- Structural Carbohydrates (NSC)

The NSC are carbohydrates that do not make up the structural, fibrous portions of the plant. They are measured and include water soluble carbohydrates (glucose, fructose, and other sugars) and starches. It is recommended that the NSC be below 10% in horses with Equine Metabolic Syndrome, Diabetes, or Cushing’s Disease. Throughout the daylight hours, plants accumulate NSC and at night, those accumulated NSC are converted to cellulose and other fibers, making the NSC content of pasture grass cyclic. Therefore, when allowing horses with a metabolic condition to graze pasture, it is best to turn them out on to pasture in the early morning when sugars are low in the pasture grass and never allow grazing in the evening when sugars are high in the grass. If you are producing hay to be consumed by horses with the aforementioned conditions, hay should be cut in the early morning hours to obtain the least amount of NSC possible. Furthermore, if your cut hay were to get rained on, the sugars or water soluble carbohydrates would be removed from the hay, resulting in lower NSC content and increased fiber percentage, making that hay ideal for horses with metabolic syndromes. Be sure to bale hay that has been rained on after the hay has had a chance to dry to avoid any potential mold or heat damage issues.

6. Total Sugars Invert (TSI)

At Ward Laboratories, Inc. we do not measure water soluble carbohydrates, however we can measure the amount of glucose and fructose in a feed as TSI.

7. Starch

Starch is an indicator of feed energy. Unfortunately, when consumed, feed is broken down into glucose units which contribute to metabolic related issues. Starch, in addition to water soluble carbohydrates or in our lab TSI, is the measurement of NSC. To reiterate the very important recommendation from above; TSI + Starch should be less than 10% in a forage or hay to be used to manage a horse’s metabolic condition through the diet.

In conclusion, when feeding a horse with a metabolic condition, avoid grain as it is high in starch and choose a low quality grass hay that is at or above 10% crude protein on a dry basis. Keep the non-structural carbohydrates to less than 10% of the hay or forage you are feeding. Following these guidelines should prevent bouts of laminitis and keep the metabolic condition in check.


	

4 Considerations For Feeding Hail Damaged Forage And Crop Residues

 

Here in Central Nebraska we have experienced several mid-summer thunderstorms. These hail producing storms have wreaked havoc on crops and forage productivity, particularly in the Broken Bow and Ansley areas. As producers move forward with crop insurance, they will also be scrambling to utilize what is left of their standing row crops and forages. There are three laboratory tests I would recommend to make an informed decision about the remaining forage. Then depending on the results of your laboratory tests, you can determine what your most economical option is.

1. Nitrates

Defoliation due to the pounding hail results in decreased photosynthesis within the plant. This means that the plant can not convert nitrates to protein. The root system of the plant still continues nitrogen uptake, although the plant cannot utilize these nutrients, resulting in the potential accumulation of nitrates in the plant. Nitrate (NO3 – N) levels between 1400 – 2000 ppm can result in abortions while levels higher than 2000 ppm can result in sudden death if not diluted with other sources of roughage. Therefore, nitrate testing of hail damaged forages is highly recommended before making a decision to graze, hay or ensile the forage.

2. Mold and Mycotoxin Potential

Hail damages the outer cell wall of the plant. The cell wall is an immune defense similar to skin on animals. It prevents infectious agents from penetrating, proliferating and using the plant as a food source. When the cell wall is damaged, opportunistic molds may infiltrate and grow. Consequently, when haying or ensiling forage, testing for mold counts is important. Mold counts above 1 million cfu/g impact animal health and lower production potential.
If the forage is a grain producing forage such as corn or milo, a producer may want to inspect the crop to determine if grain has been produced. If there is grain and it is damaged by the hail, mycotoxins become a potential risk when feeding to livestock. Mycotoxins presence may be present even in the absence of a high mold count. If you suspect mycotoxins may be an issue, remember mycotoxins and molds are often produced together however, the absence of one mycotoxin does not mean conditions were not ideal for another mycotoxin to emerge. If haying the hail damaged forage, proper drying can cut down on mold and mycotoxin presence. If ensiling, proper fermentation and additives may reduce the risk of having these agents in the feed.

 

3. Relative Feed Value

The relative feed value (RFV) will be less in a hail damaged forage or crop than its intact counterpart. Defoliation caused by the hail results in the removal or the leafy mass of the plant and what remains is the stocks and stems. These parts of the plant are lower in protein and higher in fiber, which results in a lower relative feed value. Additionally, this also means lower total digestible nutrients (TDN), and net energy of gain (NEg), lactation (NEl), and maintenance (NEm). Therefore, when feeding hail damaged forage, testing the protein and energy of the feed is important to determine how much energy and protein supplementation will be needed to meet production goals.

4. Economics

The last thing to consider, and the most important to your bottom line, when determining how to feed a hail damaged forage is what is the most cost effective delivery system based on the results of feed reports. If the nitrate reports came back low and you have the means to supplement cattle in the field to meet energy and protein needs, grazing may be the most cost effective option. Haying may also be an option under that scenario, however, if selling the hay profit margins may be small do to the lowered feed value and potential mold risks associated. Additionally, when haying you must input equipment and fuel costs associated with cutting, windrowing, and baling. If the nitrates levels have been reported between 2000ppm and 3000 ppm ensiling the damaged forage may be a good option as the nitrates can decrease by up to 50% and then be fed back to the animal. Equipment, fuel and storage costs must also be taken into account for ensiling the feed. In the case of moderate nitrates, haying and mixing with a high quality forage, such as alfalfa, to both dilute the nitrates to the appropriate level and meet the difference in protein and energy provided by the damaged forage and the animals requirements, may also be a viable option. Finally, if the nitrates report is high, utilizing the forage as a fertilizer for next years crop may be the only option.

When determining how to best utilize hail damaged forage, always take nitrates, mold and mycotoxin risks into account as well as the lowered feeding value. Consider the man power, equipment, fuel and supplementation costs associated with each option. This will allow you to make the most informed and cost effective decision possible.