Take caution on frost-damaged sudangrass and sorghums

Written by Dr. Jim White on .

A good frost will release prussic acid from growing sudangrass, Johnsongrass and sorghums. The prussic acid is poisonous to livestock.

I often get a simple question: “How much just frozen sudangrass/sorghum/Johnsongrass can I feed?”

This question is similar to asking, “How many chambers do I load when playing Russian roulette?”

The right answer is, “Don’t play Russian roulette.”

If the producer asking doesn’t quite like my flip answer and presses on, I have a simpler way explaining how much frost-damaged sudangrass and sorghum cattle should eat: zero. Once the frost has hit growing sudangrass, Johnsongrass or sorghum, you must wait for at least a week before allowing cows on it. You will be glad you did.

Most of the prussic acid in plants exists as a bound, non-poisonous chemical called dhurrin. Dhurrin is a glucoside. When dhurrin reacts with the enzyme emulsin, extremely toxic compounds form. We call it HCN for hydrocyanic acid, prussic acid, cynide. The production of prussic acid is drastically increased when plant tissue is damaged, and freezing is particularly conducive to prussic acid formation. Moreover, chopping, stomping or chewing plant tissue will increase prussic acid release.

When prussic acid is absorbed the animal, it combines with hemoglobin, depriving red blood cells from taking on oxygen. The blood is actually able to transport oxygen, but the body tissue can’t get it. Animals smother. Affected animals will have bright red, oxygen-saturated blood—a distinctly different color than the chocolate brown blood of animals with nitrate problems.

Straight sorghums will have the highest levels of dhurrin, and, as a general rule, the shorter the sorghum, the higher the level. In other words, grain sorghums have more than dhurrin thanforage sorghums. sudangrass will have the least, and Johnsongrass is between the sorghums and sudangrass. Millets seem to not have the problematic concentrations. Wild cherry is known to produce dhurrin, and animal problems have been reported when the wilted leaves are eaten—particularly if the leaves had been either storm damaged or pruned.

HCN-dhurrin concentration will decline with age of the plant. In forage sorghums, this can be particularly frustrating because forage quality drops rapidly with maturity. HCN concentration will be higher in leaves than in stalks. The highest levels will be found in short, young, sorghum regrowth, particularly in the sucker as those are pure leaf tissue. A common recommendation is to let plants reach at 24 inches high prior to using. Plant stress and increased nitrogen fertility tend to increase HCN-dhurrin concentration, consistent with what is seen with nitrate concentrations in sorghum species. Maintaining adequate potassium and phosphorous fertility helps lower incidence.

Challenges with nitrates and prussic acid are often confounded. The plant species involved, the animals affected, the visible symptoms, and the growing conditions are similar. However the compounds collect in different parts of the plant, prussic acid is highest in the leaves, nitrates are highest in the lower stalk. Prussic acid is very labile, it dissipates from the forage quickly after harvest-insult. Nitrates do not. Thus, we generate recommendations of manageable nitrate levels in rations, say 0.25 percent for milk cows. With prussic acid, 0.1 percent or 1,000 ppm is toxic, but we will have drastically lower prussic acid levels in the forage by the time we get the lab results back. Instead of developing manageable prussic acid levels for rations, we wait for the levels to decline. When munching on standing sorghums, cattle select for the leaves and against the lower stems. Grazing behavior biases against the animals eating more nitrates. Grazing behavior biases toward them eating more prussic acid.

Ruminants are more susceptible to prussic acid poisoning than horses or swine. Toxicity symptoms: include anxiety, progressive weakness and labored breathing— followed by death. Animals may show increased rate of respiration, increased pulse rate, gasping, muscular twitching and convulsions. Some deads may have no visible symptoms. If a relatively large amount is eaten quickly, the animals will die suddenly. A more likely scenario is that cattle eat smaller quantities of the forage over a longer time. First observations for symptoms are: salivation, then a gradual increase in respiratory rate followed by staggering, falling, severe convulsions and death. Veterinarian colleagues have told me that animals that survive two or three hours after onset of symptoms will most likely recover. If you see any symptoms, immediate veterinarian intervention is the order of the day.

Action items to avoid/reduce prussic acid issues:

Do not to graze sorghum, sudangrass or heavily infested Johnsongrass fields with young, short growth. Plants two feet tall should be low-risk. Grain sorghum regrowth can be especially troublesome. Saying that we should have some sheep come in to clean up the sorghum regrowth on the frost is similar to saying that we need distemper to come in and clean up the barn cats; expect high mortality.

Delay grazing sorghum species pastures for a week following a frost; it will frost first on low-ground fields. Frost kill may be uneven, the sure visual trigger is that the forage is dried out, and brown in color (brown as in paper-bag brown).

Do not allow such pastures to be grazed when initial frosts are likely.

Do not turn hungry cattle onto a pasture of sorghum species. Feed them prior to turn out. The best thing to feed them is a concentrate, say at least half a percent of body weight as Cattle Charge.

In standing plants, after a killing frost, the prussic acid will usually have dissipated after two days. That is about quickly as you can expect the dissapation. Waiting a week is a better recommendation for the field. Harvested sorghum silages and hay will release prussic acid over time. In hay, it will usually occur by the time it has finished the sweat, and in silages at terminal pH (two to three weeks) the prussic acid has dropped off.

Consider restricted grazing via a strip-graze configuration for the pasture. This increases the proportion of lower plant that the cattle consume, which reduces the proportion of leaf in the diet (where prussic acid concentrations are highest).

Culling for profit

Written by Dr. Jim White on .

If she costs too much to keep, make the most you can on the cull

In a year like this, when forage supply is low, it is an expensive proposition to carry unproductive cows. Moreover, the value of lean beef is currently high and corn crop projections have reduced the price of corn. It might be an opportune time to add profit to cows who aren’t paying their way.

Selling cull cows tends to be an activity that producers allow to happen on its own. You don’t strategically time the sale; you tend to sell when you preg check and wean. Of course, that’s the same time everyone else is doing it. If you can move the sale of the cow a couple of months either way, the market might be better due to lower supply.

Given market conditions, commodity prices and general market timing, it can make economic sense to put cull beef cows into a feed yard.
One path toward generating more value for cull cows is to fatten the cow for about three months for the “white fat” market. To do that, put cows on a high-concentrate diet, and feed as if they are feedlot heifers. The time it takes to put gain on moves the marketing of the cows from the typical lower prices at weaning to a time of the year with typically higher prices paid for cull cows.  

Your forage requirement is dramatically reduced for feeding out cull cows compared to carrying cows. Gestating cows will often get 20 pounds of hay per day. A cow on a finishing diet gets two to five pounds of hay, with the balance of her diet consisting of a grain ration. The amount of finishing ration that a thin cull cow will eat in a dry lot can be surprising. Cows on finishing diets will eat 20 to 30 percent more pounds of dry matter than you might expect. But from an efficiency perspective, this is gratifying—their ADG will also be higher than expected.

Making feeding cull cows work
Know your market—when and where cattle are going to be sold. If the market demands that they be white fat, they need to be fed with as little forage as possible for at least 10 to 12 weeks. And, they need to be sound—not lame, no broken-mouth cows. At best they will be thin, having just weathered the nutritional drain of a nursing calf. This provides a big frame to hang a lot of flesh on, and in this condition, they’re more efficient at gaining than if they were already fleshy.

Have them gain fast and as efficiently as possible. A typical backgrounding ration will have an energy level of 0.48-0.50 Mcal. Cull cows would be expected to gain three pounds per day on that. If you push the energy level to that of a typical finishing diet, say 0.61-0.62 NEg, you would expect cows to gain over four pounds per day. High rates of gain reduce yardage. In a forage-short year, high energy diets spare forage. Finish with high energy rations, 0.61 to 0.62 mcal NEg which roughly corresponds to eight to 10 percent forage; eight to 10 percent of a 40-percent feedlot supplement; and 80 to 85 percent corn.

Use growth promotant feed additives where possible (Bovatec or an ionophore).

Aggressively implant. This will tend to increase the protein requirement of the cows along with the average daily gain and feed-to-gain ratios.

Use several steps over a two to three week period to get them on full feed.

You can start them on Cattle Charge or Full Throttle. Add corn at roughly 0.75 to a pound up to two pounds. Keep them on that for two to three days, then increase another two pounds. Stop when they don’t clean up the ration.

If using a self-feeder

If you wish to exploit a forage base and self-feeder, use Cadence 50 C. Here you can expect approximately the upper two-pound range to close to three pounds average daily gain.

If you have no interest in restricted feeding, you can finish on Endpoint at 200 pounds with 1,800 pounds of corn. Here you would be targeting 3.5 pounds of average daily gain on cows.

If bunk-feeding, bunk space is critical. Remember cows are much bigger than the usual feedlot calf—10 inches of bunk space is not enough. It’s better to double bunk space. Shoot for 20 to 24 inches per cow.

Don’t feed the parasites. Vaccinate and treat for parasites. And as you are figuring your return on investment, don’t forget that you need to budget higher transportation costs. You’ll get 29 to 31 head per pot load.

Dr. Jim White is ruminant nutritionist for MFA Incorporated.


Silage questions and answers

Written by Dr. Jim White on .

I get questions. And silage questions are among the top. I’ve gathered a few (and left off the names to protect both innocent and guilty).

Q: Is it true that high nitrates can kill cows? What dose? And why?
A: Smothering can kill cows. Excessive nitrate consumed can become nitrite in the rumen, and nitrite really holds on to oxygen. Nitrates are not always toxic to animals; most forages contain some nitrates (plants like handling nitrogen as nitrate). When feeds containing nitrates are consumed by ruminants, nitrates are changed in the rumen to ammonia that is used by rumen bacteria.

That is the good news. The bad news is that nitrite is one of the intermediate products in the breakdown of nitrate and is the cause of nitrate poisoning.

Some nitrite is absorbed, and nitrite in the bloodstream changes hemoglobin to methemoglobin. Hemoglobin carries oxygen, but methemoglobin is incapable of carrying oxygen. The toxic level depends both on the amount of nitrate in the feed, and how fast the feed that contains nitrate is consumed.

Nitrate concentration will spike up for a couple days after a drought-breaking rain. When drought-stressed plants get water, they try to make up for lost time, and nitrate levels increase.

Although nitrate levels in drought-stricken corn may be high, ensiling usually reduces more than half the nitrates. For this reason, nitrate toxicity rarely occurs when feeding ensiled drought corn. However, if drought damage was extreme and high levels of nitrogen were applied to the soil, a nitrate test on the silage should be conducted. Rate of nitrate intake is the most critical factor influencing possible toxicity. Cows grazing corn stalks are unlikely candidates for nitrate issues—they do not eat the part of the plant that has the nitrates. Nitrates accumulate in the lower base of the plant, the part cows want to leave behind if they have a choice.

Likewise if you have to get safe green chop right away, raise the chopper to take the plants just under the ear. Green chop should be fed the day it is harvested. As mentioned earlier, the nitrate breaks down to nitrite, and it is the nitrite that hogs up the oxygen in the blood as greenchop nitrite levels grow higher.

Q: What is the best moisture content to ensile drought stressed corn?
A: If you had the chance to chop corn at the best moisture content for silage, it would be 65 to 68 percent moisture. Moisture levels lower than 50 percent are low for silage. Below 50 percent is workable, but excluding air becomes a challenge.
The silage will mold if air is able to get in, so adequate sealing is important. Excluding air reduces spoilage, which saves feed (which this year saves you big money).If the corn plants did not set ears, it will tend to stay wet until it dries up, dies or a good frost comes.

Q: What is the feeding value of drought-stressed corn silage?
A: Corn silage drought stunted to less than 20 bushels per acre will have about 75 to 80 percent the total digestible nutrients of normal silage. So, if normal silage has a TDN of 72 to 75 percent on a dry matter basis, drought silage will be 54 to 60 TDN, which is adequate for many applications. It could be supplemented with energy in some cases.

Absence of ears does not imply that corn silage lacks fermentable energy. It’s actually the contrary—the kernel was not a glucose sink, and there are a high level of soluble sugars with nowhere to go. As the corn plant matures, the energy level and dry matter yield increases.

I recommend allowing corn to develop as fully as possible, even if ears and grain are lacking. There are wide variations in the nutritive content of drought-stressed corn silage. Get it tested so you know what you have to work with. If you get the forage test back that shows high potassium, expect high nitrates, which you should expect on stressed plants.

If the plants were very young, say waist high, tasselled out and dried out, you might see a protein level in the mid teens. And, in that corn, nitrates might get as high as 0.9 to 1 percent, which means that you would need to limit-feed the material. Feed at levels to keep rations below 0.25 percent nitrates for wet cows and 0.44 percent for growing animals or mature adults at maintenance.

Q: Adverse weather conditions present me with major challenges. First, I am not able to produce enough forage. Second, the forage quality is hit and miss. It is either really good (the drought-stressed alfalfa has a relative feed value over 200), or it is really bad (the corn with no grain in it). My questions are: should I buy more forage? Or, should I keep forage at a minimum, and bring in concentrates of higher fiber?
A: A common question these past two years. First, it is essential to evaluate your particular situation, including effects on cash flow. The other day I was talking to an accountant. I was whining about how they had costed out some inputs. And I asked, “Why did you do it like that?”
The accountant said, “To get the right answer.”
That seemed a good reason—the way I wanted to do it was to not consider some costs. Sure, that made for cheaper feed, but it was an inaccurate number, which would have projected more income-over-feed cost than there really was.
If you can get additional price-competitve forage, then importing forage is certainly a viable option. But consider what you’re buying. Work with a known dealer, or have an agreement for minimum quality. Also consider the forage’s availability, palatability and suitability. Drought-stressed material might also have high levels of nitrates or increased incidence of poisonous plants.
If you hold down the amount of effective fiber fed to milk cows, you will tend to want to feed lower amounts of starch-NSC to them.
When faced with a true shortage of forage, feeding lesser amounts of coarse material is a tactical approach to the inventory problem. As the pounds of NDF fiber from forage declines, the minimum diet ADF increases and the minimum diet NSC decrease.
To achieve the energy level in the diets that your cows need, you can consider supplementing MFA Dairy Heartland feed to take pressure off the shortage of forage availability.

Get calves from your cows

Written by Dr. Jim White on .

Body condition is critical for breed-back

If you follow a body condition scoring system—evaluating the cows to keep them in good flesh—you can likely keep a healthier and more easily bred herd. But if you’re behind now (say you’re looking at a cow that calved with a BCS less than 5), you’ll have a hard time getting her bred, even if pastures are in good shape. If that’s the case, preg-checking cows this fall will be crucial.

On thinner cows, you need to start working them into adequate flesh now—a BCS of 5 or better. We often see the summer as a time to let cows slide—they can eat all they want and there’s no real reason to check on them every day.

The first thing in the process of keeping cows in the right body condition is to understand where you’re at with your herd.

You need to evaluate forages. By mid- to late-summer, mature fescue makes your forage base low in protein and energy. Forage availability may also be compromised. This situation will be more troublesome if you calved late, and your breeding season has crept into the summer.

If the cows are thin, and still need to get bred, the way you supplement cows becomes paramount.

As the summer wears on, I expect to supplement protein; maybe not to the extent that I would on an older stockpiled pasture, but I would check and see if the cows will respond to protein.

Supplying supplemental protein helps in a couple of areas. First, it supplies protein to the rumen bacteria. This increases bacterial growth and reproduction, and it aids in rumen breakdown of forages, which increases the nutrient yield from mature plant material. This increases energy intake and availability. It leads to increased cow weight gain.

Second, it increases the actual protein available for absorption by the cow. Additionally increasing availability and uptake of protein and energy levels will improve cow reproductive function.

If forage availability is good but mature, a couple of pounds of a supplement is called for. Good choices would be handfeeding Trendsetter or 20-percent cubes, offering MFA Salt mix No. 1 or using 20-percent protein tubs. Any of these products could help meet the cow’s protein and energy requirements.

While on pasture, cows might be able to achieve their energy and protein needs, but it will be impossible for them to meet all their mineral and trace mineral needs. A quality, loose, free-choice mineral is needed. Your mineral should be matched to your forage base and kept available at all times.

Cows will come into summer, gaining weight through mid-season but subsequently losing some of these gains. If cattle are managed to gain and maintain weight through the summer and into the fall, they enter the winter in better condition. That means there’s a chance you’ll need less supplemental feed through the winter to maintain condition and performance.

Keep her in the middle
Most herds carry cows at BCS between 3 and 7 through the year, with the goal of reaching between 5 and 7 before calving. There is predictable loss of condition after calving. Depending on the cows and availability of feed, the loss can be dramatic. Achieving a condition score of 5 to 7 prior to calving is important for breed-back. Research from the University of Virginia shows that 91 percent of cows at BCS 5 showed signs of estrus by 60 days post-calving. Only 61 percent of cows with BCS 4 reached estrus in the same timeframe, and just 46 percent of cows at BCS 3 or less showed signs of estrus within 60 days of calving.

Dr. Jim White is ruminant nutritionist for MFA Incorporated.

READ the originally published story HERE.

Solutions for silage problems

Written by Dr. Jim White on .

A troubleshooting guide for forage and corn silage

*Excessive effluent (seepage or run-off)

•    Ensiling forages too wet (low dry matter [DM] content) for the silo type and size.
•    Weather did not allow the forage to be field-wilted properly before chopping.
•    Forage was not “conditioned” when it was cut.
•    Forage was placed in a window that was too bulky for the time allowed for field-wilting.
•    Whole-plant corn, sorghum or cereals were harvested at an immature stage of growth.
•    Some aggressive enzyme additives increase run-off and have caused silage to fall and ooze out of bunkers.

•    Follow more narrow weather forecasts to plan forage management decisions.
•    Take advantage of new mowing, cutting and conditioning equipment technologies.
•    Coordinate the merging of windows/swathes with the time of chopping.
•    Monitor the maturing/drying process of each field of corn, sorghum or cereals so harvesting time can be scheduled properly.

Caution: Effluent has a very high biological oxygen demand. It should be contained near the silo of origin and not allowed to enter a nearby pond or water course.

*Large variations in the ensiled forage’s dry matter content and nutritional quality

•    Use multiple silos and smaller silos, which improve forage inventory control.
•    Ensile only one cutting and/or variety of “hay crop” forage per silo.
•    Minimize the number of corn and/or sorghum hybrids or cereal varieties per silo.
•    Shorten the filling-time, but do not compromise packing density.
High concentrations of butyric acid and ammonia-nitrogen, particularly in hay-crop silages
Note: These two components indicate that a forage underwent a clostridial fermentation.

•    Chop and ensile all forages at the correct DM content for silo type and size.
•    Properly pack to exclude as much oxygen as possible, which will minimize the loss of plant sugars during the aerobic phase.
•    Apply a homolactic bacterial inoculant to all forages to ensure an conversion of plant sugars to lactic acid.
•    Avoid soil contamination throughout all mowing/ conditioning, harvesting and silo-filling operations.
•    Note that wilting legume crops that are rained on are at greater risk of clostridia growth, the soiling has increased, and the plant matter has lost soluble carbohydrate. If it is not possible to control percent DM by wilting, adding sugar (corn syrup) solids is helpful.


* High concentrations of acetic acid, particularly in wetter corn, sorghum and cereal silages

Note: This indicates the forage underwent a prolonged, heterolactic fermentation. The silage will have a distinct “vinegar” smell. It is common to see a one- to two-foot layer of bright yellow, sour smelling silage on the floor of bunker, trench or drive-over pile silos with wet corn silage.
•    Ensile all forages at the correct DM content.
•    Use a homolactic inoculant to ensure an efficient conversion of crop sugars to lactic acid.


*Heat-damaged silage
Note: This silage will be dark brown and have a strong burnt caramel/tobacco smell. This is a common problem with drier legume silages.
•    Temperature of silage exceeds 130 degrees.
•    High feed temperatures will cause protein to be “bound.” Protein reacts with a carbohydrate and acts more like fiber-lignin than protein.
•    Palatability will be good, but protein value is reduced.
•    Most heat in silage is from respiration. Respiration will continue as long as oxygen is available. Being able to quickly achieve anaerobic conditions will limit heat damaged silage.
•    High silage density coupled with rapid and thorough sealing of the silo will restrict heating to a minimum.
•    In well-managed silages, silage temperature does not increase more than 10 degrees over the ambient temperature.
•    Harvest at correct stage of maturity (not too mature!).
•    Ensile forages at the correct DM content (not too dry!).
•    Do not chop forage at too long a particle size.
•    Fill silos in a timely manner.
•    Achieve a uniform distribution of forage and a high packing density (a minimum of 15 pounds of DM per cubic foot).

*Aerobically deteriorating silage during the feedout phase
This is seldom a problem with legume silages.
•    Yeast growth occurs on silage. Yeast will not grow in the absence of air, but it needs little air (0.5 percent) to grow.
•    Bacillus may be involved, especially if the silage feels slimy.
•    Poorly packed, drier cereal grain silages with high porosity tend to be at the greatest risk.
•    Harvest at correct stage of maturity (not too mature!).
•    Ensile forages at correct DM content (not too dry!).
•    Do not chop forage at too long a particle size.
•    Achieve a high packing density.
•    Fill rapidly—fungal counts tend to increase with delayed filling
•    Maintain a uniform and rapid progression through the silage during the feedout phase.
•    Avoid feeding from large silos during warm weather.
•    Do not leave silage-based rations in feed bunks for an extended period of time, particularly in warm weather.
•    Slow the onset of aerobic deterioration by the application of an anti-mycotic at ensiling.

*Excessive “surface spoilage” in sealed bunker, trench and drive-over pile silos
•    Achieve a high packing density in the forage within the top 3 feet of the silage surface.
•    Seal the silo immediately after filling is completed.
•    Apply buffered propionic acid to the surface prior to sealing.
•    Apply sufficient, uniform weighting material to the polyethylene sheet.
        -    Overlap the sheets by a minimum of 4 to 6 feet.
        -    Consider whole truck tires that touch to weight the overlap.
        -    Whole tires are preferred over tire walls, and truck tire walls are preferred over car tire walls.
•    Prevent damage to the seal during the entire storage period.

*Excessive mold in bagged silage
•    Fungi present plus adequate moisture, air and time to grow.
•    Air-tight seal not established. In a silage that has 0 percent oxygen, the outside environment, at 21 percent oxygen, tries to push oxygen into the silage.
•    Erratic filling giving a rough bag, which allows air to channel through the silage.
•    Bags overstretched—film failure.
•    Inadequate removal rate. Should be at least a foot a day in warm weather.
•    Lack of low porosity silage—as density increases, porosity decreases. Bag density is greater at the bottom of the bag than at the top of the bag. Erratic filling may give rise to horizons where air was not expressed and fungal growth was greater.
•    Most commonly seen molds in the Midwest in bagged silage are mucor, monelia and penicillium.
•    Ensure adequate equipment maintenance and that equipment is operated by competent personnel.
•    Avoid erratic filling rates.
•    Do not overstretch bags.
•    Ensure adequate removal rates.
•    Apply an anti-mycotic at ensiling. The salts of some organic acids are compatible with LAB inoculants.
Dr. White is ruminant nutritionist for MFA Incorporated.



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