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.


Springtime brings grass tetany

Written by Dr. Jim White on .

Cattle producers see the highest incidence of grass tetany in spring. And, over time, we have convinced ourselves that grass tetany is a shortage of magnesium in the blood (which it is by name and definition: “hypomagnesemia” is low magnesium in blood). So most producers address tetany problems by offering their cattle increased magnesium supplementation, and, once that remedy is in place, think all is well. 

The reason we associate grass tetany with spring is because of the low magnesium and/or high potassium content of rapidly growing grasses. Think lush, succulent spring fescue. In addition to the low magnesium, we have seen other factors that seem to be associated with grass tetany, many of them concurring with spring. There is the high soluble crude protein content of forages and weather stress—both for plants and animals. Lactation can play a role, too. 

Milk is a significant magnesium and calcium sink. And, we know that the nitrogen fertility status of pasture can play a role— with higher rates of nitrogen resulting in greater incidence of grass tetany. 

Meanwhile, the type of supplement offered cattle, particularly magnesium, calcium, salt and fermentable carbohydrates tend to reduce the incidence of tetany.

With so many factors involved, you can blame tetany on one or more of them. Grass tetany-hypomagnesemia may be due to low magnesium consumption. Or, it may occur due to low magnesium absorption/uptake. High potassium levels have been linked to reduced magnesium absorption. A German study showed that over 95 percent of the uptake of magnesium depends on the gradient of sodium, which implicates sodium deficiency as a potential cause for tetany. 

In other words, cows’ ability to regulate the concentration of intracellular free magnesium is directly related to sodium. The principal source of sodium for the animal will be the salt you feed.

Most of the time salt is offered to cattle free choice or forced in the diet. We know that we have to feed sodium because herbivores really like sodium, but plants do not. So without supplement, cattle will be deficient of sodium. 

Weather, fertility, species and growth stage will influence the amount of potassium in plants. The variation and imbalance of minerals in the rapidly growing lush grass triggers grass tetany. Another source of mineral concentration change might be due to frost damage, and young forage plants are particularly sensitive to frost damage. 

What are the effects of frost damage on tall fescue? March 2007 was warmer than usual, and there had been significant growth in pastures. But in April, there was a cold snap across the Midwest that resulted in substantial freeze damage to fescue stands. In the days following the event there were reported incidences of grass tetany in spring-calved beef cows. 

Researchers at the University of Missouri worked on the problem and concluded that the amount of sodium in fescue tissue was highly correlated to the freeze damage and the increased incidence of tetany. 

We might be past the final hard frost, but like 2007, there is always a chance lush grass will suffer frost damage. Now is the time to develop an appropriate strategy to reduce the risk of grass tetany this spring.

There are several factors which increase the likelihood of grass tetany. First off, magnesium is a dietary requirement for all cattle. Growing beef cattle have a magnesium requirement of about 0.1 percent of dry matter; for lactating beef cows, that requirement is doubled; triple that for wet dairy cows. For nursing cows, the requirement for calcium increases. So do the requirements for magnesium. The heaviest milking cows are at greatest risk of grass tetany. Storms, trucking, running the self-feeder empty or other stressors that cause cattle to stop eating can precipitate grass tetany. 

An obvious approach to defending against tetany is offering a salt mix with magnesium. This is generally the fastest and most certain method of addressing grass tetany. If modest protein and energy supplementation are needed where labor is an issue, 20-percent tubs with magnesium are a good choice. If the forage base is protein-and-energy adequate, products like MFA’s Hi-Mag Mineral, MFA Tasty Mag Mineral or Mag-Ade meal would be options. 

If you are hand-feeding cubes or a supplement at recommended rates, the likelihood of tetany is remote. Lactating cattle should consume 15 to 25 grams of magnesium per day. If a feed is on offer at all times, say a free-choice mineral, the supplement disappearance should be checked frequently. Magnesium is not well stored in the body, so frequent consumption is needed. Solubility (or bioavailability) is important. The more soluble a magnesium source is, the more bioavailable it is. 

Dr. Jim White is ruminant nutritionist for MFA Incorporated.

Originally published in the April Today's Farmer magazine ©2013 MFA Incorporated. All rights reserved. Here is a LINK to the original version of this story.

Managing in the mud

Written by Dr. Jim White on .

As a columnist, one way to tempt the weather is write about managing against it. Maybe if we talk about mud, it will rain. To seed those clouds, I’ll quote liberally from extension cattle specialist at Mississippi State University Jane Parish from an excellent piece she put together about managing through the muddy season.

It usually is the muddy season right about now in the Midwest—late winter and spring tend to be the time we’re most likely to get frequent precipitation. It’s also the time we’ve burned through available forage, so we are feeding hay and often have the cows bunched up to calve. All of this makes for traffic on wet soil—and mud. We compound it with traffic from tractors and trucks as we put out hay.  

Mud lowers insulation value of the hair coat. That’s especially hard on new calves. Muddy udders also affect calf health. For cows, muddy feet make for the risk of foot rot.

Parish points to an additional factor here in fescue country when it starts to warm up. “Another special concern in dealing with mud on cattle operations is that of animals consuming endophyte-infected tall fescue,” she said. “Cattle suffering from fescue toxicosis typically spend extended time in mud holes, making them more susceptible to health and performance complications related to mud. Even in droughty conditions, mud may accumulate in shaded areas where cattle congregate. Concentration of urine and hoof action will cause deep mud holes to develop in toxic tall fescue pastures. Cattle experiencing fescue issues often have large amounts of mud caked on rough hair coats.”

Moreover, those cows we’re trying to keep in condition for breed-back are spending energy slogging around. When hay supplies are tight, we hate to see anything that knocks our carry-through efficiency.

Here are a few management tips from Parish:
•    Identify high-traffic areas.These are places that cattle or vehicles move across on a frequent basis, e.g. gates, cattle handling areas, and feeding/watering areas. Ground-level protection from mud development in these areas usually are high-traffic ground coverings: concrete feeding pads, geotextiles, rock base. If the covered area is too small (say a concrete feeding pad/apron) it might become surrounded by deep mud that the cattle fight through for every feeding bout.  
•    Bedding is a useful environment improvement practice. There comes a point in a wet and cold calf’s life where they would rather rest than eat. You’ll notices stressed calves resting on newly unrolled hay rather than eating.  
•    Hay feeding is a potential source of pasture damage and mud development. If one or only a few hay feeding locations are used throughout the entire winter feeding period, mud tends to become a problem more quickly in those areas.
•    From the road, mud conditions might look slight, when they are in fact more substantial. A glance across the pasture might not be reflective of the struggle animals have at the feeding ring. Knee-deep mud will stress your herd.
•    Frequent movement of hay feeding locations around a large area may result in more widespread damage to pasture plant cover but less severe mud in any one location. Be aware how mud problems might develop and plan to minimize them. If you start to feed hay at the front of the pasture near the gate (which might seem the easiest place to start), you might multiply mud problems as vehicle travel and hoof impact increases. It might be better to start feeding at a further end and work toward the gate.  
•    Reducing vehicle traffic through pastures can also help protect from vegetation destruction, soil compaction and rut development. Forages are particularly susceptible to damage when frosted or otherwise stressed. When possible, check cattle on foot or use the smallest possible vehicle.
•    Provide and maintain watering sources that reduce water splashing/loss. Sturdy trumps cheap. Broken waterers result in water pooling and more mud.
Mud, like taxes and whichever political party is opposite of your views, will always be with us. Reducing mud will reduce the nutrient requirements of the cattle. When you’re looking for ways to save money and make a more efficient herd, mud management might not top the list, but mud is truly a negative influence on the bottom line.
Dr. Jim White is ruminant nutritionist for MFA Incorporated.


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