Cooperative Sheep Production Meeting: Clay Center, NE

Last Saturday I spent the day in a classroom at the US Meat Animal Research Center learning about sheep production and tools put out by University of Wyoming Extension to help producers make the best possible management decisions. The meeting was a cooperation between the University of Wyoming Extension, Great Plains Veterinary Educational Center, Nebraska Sheep and Goat Producers and the US Department of Agriculture. There were three speakers each extension educators at the University of Wyoming and consultants at Master Stockman Consulting.

The first speaker was Bridger Feuz, who spoke about the economics of raising sheep.  Economics is important in sheep production to improve profits and build relationships and partnerships with bankers.  As in most of agriculture, tight margins for profit exist when raising sheep.  It is important to budget for every possibility to make the best possible decision for the operation.  The first tool Mr. Feuz introduced was the US Baseline Cost of Production.  This tool allows producers to see where they are relative to the average cost to produce sheep.  It also showed that often in years when the sheep market was down the cattle market was up and vice versa therefore supporting diversification of enterprises in ranching.  The second tool introduced by Mr. Feuz was the Partial Budgeting calculator.  This tool along with the other rest of the tools Mr. Feuz went on to describe can be used for all classes of livestock not just sheep.  It helps producers make better business decisions by answering 4 questions when making changes to an operation:

  1. What new or additional costs will be incurred?
  2. What current income will be lost?
  3. What new or additional income will be received?
  4. What current costs will be reduced?

The other tools Mr. Feuz breiefly explained were the Break-Even Calculator, the Ewe Valuation Calculator, Market Comparison Tool, and Net Present Value Analysis used for pasture improvement.  All these tools can be found at www.uwyoextension.org/ranchtools.

The second speaker was Barton Stam, a forage specialist.  He spoke about meeting the nutritional needs of sheep.  First, Mr. Stam stressed the importance of providing livestock with quality water.  Ward Laboratories, Inc. can run a livestock suitability test to help producers determine if their water is fit for animal consumption.  He recommended timing the grazing of warm and cool season grasses to optimize protein content of the grass with the protein needs to the animal.  Additionally, he recommended grazing the plant before it had reached maturity.  By grazing before the grass has produced a seed head, the potential to graze regrowth later in the season is more likely.  A plant grazed before reaching maturity will continue to grow and trying to produce a seed head.  Once the seed head has been produced however, the plant has achieved its goal and will no longer to continue to grow and produce valuable forage.  His take away was to graze grasses before they reach reproductive maturity to obtain better nutritional value for the animal and potentially stockpile more forage for later grazing.  He also recommended sampling cane type grasses for prussic acid and nitrates.  Producers can send those samples to Ward Laboratories, Inc. for analysis. Mr. Stam introduced the Stocking Rate Calculator as a useful tool for sheep producers to use in decision making.

The third, and final speaker for the morning was Dr. Whit Stewart.  The topic Dr. Stewart addressed was parasite control and resistance of sheep parasites to anthelmintics. The American Consortium for Small Ruminant Parasite Control was introduced to the group of producers as a good source of information regarding parasites, dewormers, and resistance issues. Dr. Stewart recommended producers consider using either the McMaster test or DrenchRite® to determine which dewormers are going to be most effective on their operation and if they have resistance issue with specific anthelmintics. He concluded by speaking about the future potential for natural compounds such as condensed tannins to be utilized to fight parasites.

Overall, each speaker introduced new tools to help producers make the best possible decisions.  Like the tools introduced by the speakers, feed and water analysis at Ward Laboratories, Inc. are also tools to help ranchers make the best possible informed decisions.

Prussic Acid and Nitrates in Sorghum and Sudan Grasses: Proper Sampling for Grazing Animals

Often, Ward Laboratories, Inc receives sorghum samples and producers want us to test prussic acid and nitrates.  My recommendation would be to send two separate samples when testing for grazing purposes because prussic acid and nitrates accumulate in different parts of the plant. Prussic acid accumulatesin the leaves of the grass in contrast to nitrate which accumulates in the plants lower stock.

Prussic acid is also known as hydrogen cyanide (HCN).  The compound is present in the leaves of the plants in a compound called dhurrin.  Under normal conditions, plant membranes separate dhurrin from the enzyme responsible for hydrolyzing HCN from dhurrin. Monogastric animals and hindgut fermenters such as swine and horses, typically do not have an issue with prussic acid poisoning as stomach acid deactivates the enzyme.  However, ruminants such as cattle, sheep and goats, are more susceptible to prussic acid poisoning due to the chewing of their cud.  As those animals ruminate, the cell membranes are damaged allowing the enzyme access to dhurrin, thereby releasing HCN into the rumen.  The HCN is then absorbed directly into the bloodstream where is binds hemoglobin.  The bound hemoglobin can not transfer oxygen to individual cells and death by asphyxiation is the result.

An additional risk for prussic acid poisioning is posed by stressed and damaged plants , this is when it becomes toxic to non-ruminant livestock.  Drought stressed plants may accumulate more unbound HCN in their leaves.  Frost damaged plants also have unbound HCN in their leaves due to the frost having broken the cell membranes allowing enzyme access to dhurrin.  In the case of frost, outer cell membranes have also been damaged, therefore waiting 4-5 days before grazing is sufficient assurance that the hydrogen cyanide gas has escaped the plant leaves.  After a frost, regrowth is toxic past the 4-5 day time frame and should certainly be tested before turning animals out to graze.

So, for testing prussic acid take leaves from 20 different plants across the field for a representative sample.  Do not cut the leaves and avoid as much damage as possible.  Immediately place all leaves in a gallon sized zip lock bag. Either ship the sample overnight, or drop the sample off at Ward Laboratories, Inc. as soon as possible.  When we receive your sample, we will refrigerate it and run it as quickly as we can as to not loose any HNC and to avoid a false low value.  Samples reported at >200 ppm as received are considered toxic and allowing animals to graze would result in a rapid death toll.

I have covered nitrate toxicity in other blogs including: Do I Need to Test for Nitrates?, 6 Cautions When Grazing Cover Crops, and 4 Considerations for Feeding Hail Damaged Forage and Crop Residues. So, for testing nitrates in sorghum and sudan grasses for grazing go into the field and cut the plant at the point where you plan to pull animals off.  Then, cut 4-6 inches above that, with this small piece use plant shears and snip it into pieces.  Repeat this with 20 randomly located plants across the field.  Then mix all the small plant pieces together and take a representative sub-sample from that pile.  Place them in a zip lock bag and send them to Ward Laboratories, Inc. for nitrate analysis.

In summary, test the leaves for prussic acid and the stocks for nitrate.  It is always important to take a representative sample for the most accurate results and informed production decisions.

Additional Resource:

Nitrate and Prussic Acid Toxicity in Forage

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.