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Dealing with lower digestibility in the 2015 corn silage crop

Gene P. Gengelbach, Dan Schauff and David Spangler Published on 29 October 2015
silage tractor

Although the Southeast has suffered through some horrendous flooding in the last few weeks, most of the country has experienced a warm, dry period this late summer and early fall.

Throughout the Midwest, the last six to eight weeks have been characterized by an abundance of sunny and windy days, which is conducive to rapid drying of this year’s crop. As a result, the corn silage samples coming into our lab since mid-September have averaged around 63.5 percent moisture. Starch levels are just over 35 percent, which is good, but seven-hour starch digestibility is only 81 percent, which is quite a bit lower than we would like to see. Fiber digestibility is also less than ideal since abundant moisture during early summer enabled rapid stalk growth and additional lignin production.

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Comparison of 2015 corn silage samples

Hopefully, most producers are still feeding their 2014 corn silage, but what about those who have to start feeding this year’s crop right away? What challenges will they be facing in the next few weeks?

First, drier silage is harder to pack, leaving air pockets and a spongy feeling when you walk over the bunker or pile, so density, and therefore storage capacity, is lower than normal. A good, lactic acid producing fermentation can’t take place until all of the oxygen is used up in the silage mass, and this aerobic respiration causes heating. That, coupled with the warm ambient temperature during ensiling, means that the silage will come out warmer than usual, even if no spoilage organisms are present.

Treating silage with an additive that contains antioxidants can help eliminate excess trapped oxygen so fermentation can get started sooner, and the addition of lactic acid producing bacteria can lower the pH quicker. Also, additional carbohydrates are used up during this excessive respiration, so the sugar or water-soluble carbohydrate fractions will be lower than normal, which leads to lower energy in the silage. Using a silage additive that contains fibrolytic enzymes will help break down fiber into simple sugars, which are then available for conversion to fermentation acids to speed up the natural fermentation process.

Next, because of the lower silage moisture level, the bacteria will take longer to produce the amount of acid necessary to preserve the silage, so try to avoid opening the silo for as long as possible. This long period of aerobic conditions, followed by slower acid production, permits spoilage organisms like yeasts and molds to multiply rapidly, so watch for silage that comes out excessively hot or that will reheat when exposed to air.

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Finally, because of the more mature crop, kernels will be drier and harder, so the silage – especially if it is poorly processed or non-processed – will have much lower starch digestibility this fall until the silage acids have a chance to soak into the kernels and start to soften up the starch and hydrolyze some of the prolamin proteins in the kernel. Starch digestibility will improve with time in storage; however, drier silage will not ferment to the extent that higher moisture silages do. Consequently, overall starch digestion in the drier 2015 corn silage crop may be lower this year. Time will tell.

How can we adjust the diet to help maintain production in the face of these quality issues?

  1. Since silage starch digestibility is lower, make sure to include more digestible forms of starch in the ration, such as high-moisture corn, fine-ground dry corn or pure corn starch. It will also help to increase dietary sugars by feeding molasses or dextrose.
  2. Because of low digestibility, the crop won’t feed as “hot” as you think it should because of the higher starch level. The total energy concentration of the ration will most likely have to be increased to maintain animal performance.
  3. Protein solubility will be low in poorly fermented silage, so increase the amount of soluble protein in the diet by feeding more haylage or baleage, or including some urea in the ration.
  4. Try to feed at least 6 inches per day off the silo face to keep the silage fresh.
  5. Feed enzyme products containing both starch- and fiber-digesting enzymes to help increase ration digestibility and to get the most out of your corn silage crop.  PD

Gene P. Gengelbach, Ph.D., PAS; Dan Schauff, Ph.D., PAS; and David Spangler are with Agri-King Inc.

PHOTO: Adverse weather has caused lower digestibility scores in the 2015 silage crop, which may become a feeding problem later. Photo by Lynn Jaynes.

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