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Surviving 2019 forages

Bill Weiss for Progressive Forage Published on 02 October 2019
Silage

Every forage cropping year presents challenges to both growers and users of forages; however, 2019 has been much more challenging than normal. In many areas of the country, much of the alfalfa suffered winterkill.

This was followed by a very wet spring that delayed harvest of silage and hay crops, including alfalfa, grasses and small grains. To make matters worse, the wet spring also significantly delayed corn planting, and because corn silage has become such an important forage for dairy farmers, this may have impacts well into 2020.

Because of winter and spring weather conditions, many dairy farmers are facing not only a shortage of high-quality forage, but a shortage of forage in general. Dairy cows need forage to be healthy, and dairy cows need high-quality forage to produce lots of milk. What can be done when both are in limited supply?

The first step should be calculating inventory of current forage supplies and the quality of those supplies. Because of difficult planting conditions, accurately estimating corn silage yields prior to actual harvest will be difficult, but if hay crop yields and quality were low, you should plan on harvesting additional acres of corn for silage this fall.

If corn silage is chopped at the correct moisture content, it is generally at least a good quality forage (i.e., acceptable fiber digestibility) and will be substantially better for milk production than mature alfalfa or grass. If the corn silage is low in starch because of low grain yields, that can be made up with corn grain; however, it is much more difficult, and expensive, to supplement good quality forage fiber.

There is a strong negative correlation between concentration of neutral detergent fiber (NDF) and starch in corn silage (low starch corn silage equals high NDF corn silage). For alfalfa and grasses, high NDF concentrations indicate more mature forages and are associated with low fiber digestibility and reduced feed intake and milk production when fed to cows. However, corn silage is different; high NDF concentrations are associated with a less mature forage (grain has not developed to dilute out the fiber) and often higher NDF corn silage has higher fiber digestibility. In research studies that compared corn silages with different NDF concentrations, intake and milk yields were often not affected by silage. Whereas when similar studies are done with alfalfa or grass with different NDF concentrations, intake and production usually are less with higher-NDF forage.

A primary factor affecting the nutritional value of corn silage is dry matter (DM) concentration at harvest. DM affects fermentation quality and is an indicator of plant maturity. If you will be relying on increased feeding rates of corn silage to replace lower-quality hay crops, corn silage must be good. Proper harvest time is always important, but this year with heavy corn silage diets it will be even more important.

Unfortunately, with delayed planting and potentially highly variable fields, corn silage DM may not follow typical patterns. On average, corn silage is ready to harvest about six weeks after silking; this may or may not be true this year. Kernel milk line, even under typical growing conditions, is not an accurate indicator of harvest. With late-planted corn, drydown rates will likely be slower than typical, but weather in late summer will affect rates. If late-planted corn gets frosted, it will initially appear much dryer than it is, but it will also dry down more quickly.

Because of all the uncertainty associated with drydown rates this year, dry matter of the crop should be monitored more closely than usual. Sample a few corn plants about five weeks post silking (the silage will likely be much too wet to chop) and then estimate a drydown rate of 0.5% units per day (actual rates can be as high as 1% unit). Sample again when estimated DM is around 28% (28-initial DM/0.5 = days until next sampling). The silage will likely still be too wet, but you can start to get a more accurate estimate of when chopping should occur (generally 30% to 35% DM). Follow good silage-making practices (use high-quality inoculant, rapid filling, good packing, sealing silo) to keep shrink low and quality high.

Lastly, late-planted corn may have different nutrient composition than what people are used to. Sampling corn at chopping for nutrient analysis will help determine the best way to use the silage in diets.

Even with higher corn silage inclusion rates, many dairy farmers will still have to feed some lower-quality hay crop forage. The most effective way to reduce negative effects of feeding lower quality forage is to keep the concentration of forage NDF in diets below about 25%; and the worse the forage, the more the concentration of dietary forage NDF should be reduced. However, because of the risk of acidosis, generally as forage NDF concentration is reduced, dietary starch concentration also should be reduced so the forage is being replaced by high-fiber byproducts, not by starchy grains.

Whole cottonseed is an excellent choice to replace lower-quality forage. Another approach to reducing the negative effects of lower-quality forage is to reduce its particle size prior to feeding. This can be done using the total mix ration (TMR) mixer, but it is important that only the low-quality forage is chopped finer, not the entire diet.

Another option, if possible, is to match forage quality to animal requirements. Dry cows, growing heifers and late-lactation cows need much less energy than early lactation cows, and lower-quality forage can be targeted to those groups, saving the better forage for the high production groups.

The keys to reducing the negative effects of lower-quality forage and limited supplies of hay crop silage and hay is to increase corn silage inventories going into this winter, make the corn silage as good as possible and reduce inclusion rates of lower-quality forages by increasing inclusion of corn silage and high-fiber byproducts.  end mark

PHOTO: Because of winter and spring weather conditions, many dairy farmers are facing not only a shortage of high-quality forage, but a shortage of forage in general. Staff photo.

Bill Weiss
  • Bill Weiss

  • Department of Animal Sciences
  • Ohio State University
  • Email Bill Weiss

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