In many parts of North America, there can be a surplus of whole-plant corn acres left over for corn grain harvesting once the silage tonnage requirements are met.
For dairy and beef operations, this grain fraction does not have to be taken as dried shell corn, which would require specialized combining and drying equipment.
Instead, there is the option to take high-moisture corn (HMC) grain crops, using available field harvesting equipment and eliminating costs incurred during artificial drying, allowing harvest two to three weeks earlier and reducing field and harvesting dry matter compared to corn harvested for dry storage.
There are a wide variety of HMC grain-type products stored on-farm depending on the harvest method chosen. All have one thing in common: They are stored by ensiling and are prone to aerobic instability if they are not ensiled, stored and fed out correctly.
Types of HMC grain products
The types of HMC grain products produced on dairy farms are high-moisture shell corn (HMSC); “earlage,” which is itself a generic term that encompasses high-moisture ear corn (HMEC); snaplage and, more recently, toplage, which is somewhere between high-cut corn silage and snaplage.
HMSC is the moist corn grain combined somewhere between 68 percent and 72 percent dry matter (DM), or 32 percent to 28 percent moisture content, with a desirable DM target of 70 percent (or 30 percent moisture).
Damage to the corn kernel at harvesting is not as big a problem as it is with dry corn, as the HMSC will be ensiled. Indeed, most HMSC is ground prior to ensiling, although it is sometimes stored whole in oxygen-limiting structures.
HMEC (60 to 64 percent DM), or cob meal as it is sometimes referred to, is corn grain and cob material harvested with a combine set to return the grain and a portion of the ground cob to the hopper. It is therefore higher in neutral detergent fiber (NDF) and lower in starch content than HMSC.
Snaplage (58 to 62 percent DM) is taken with a snapper head mounted on field choppers and processed through a kernel processor, so it contains the corn grain, cob, husk and likely some ear shank. It’s higher in NDF and lower in starch than HMEC.
Toplage is a more recent development from the Midwest taking the corn plant ear (grain, cob, husk and shank) plus the top part of the corn stover using a modified corn header. It has more NDF and less starch than snaplage.
Harvesting HMC products
The fineness of grind for HMSC will depend on the harvest DM or moisture content: The higher the DM, the finer the grind required. Harvesting these products too dry will present challenges for ensiling, aerobic stability and starch utilization in the ration when fed.
Some typical analytical values for each HMC product, in order of decreasing starch content, are shown in Table 1 along with HMSC, and typical corn silage values are also shown for reference.
The crude protein content is typically similar for all farm-stored high-moisture grain products and not useful in differentiating between the products. The percent NDF and percent starch can be used to some degree. However, as with all ensiled products, these materials must be analyzed at source for use in ration formulation prior to feeding to high-producing animals.
Many accredited forage and feed laboratories offer an NIR analysis for the more common ensiled high-moisture grain products, but some, like toplage, may not have an adequate reference database, so wet chemistry analysis is advisable.
As these are all moist products containing grain, total starch digestibility and rate of starch digestion will change during storage. Consequently, starch digestibility and rate of digestion should be analyzed and monitored, at least on a monthly basis, to allow ration adjustments as necessary.
Ensiling and feedout challenge
Originally, products like HMSC were stored in towers or silo bags. Now, ground HMSC, along with ground HMEC and processed snaplage, are often ensiled into walled bunker or trench silos, much like corn silage, or in bags.
These are high-starch, high-value products intended to reduce the farm purchase of dry shell corn. However, they need attention to detail at ensiling and feedout to ensure the maximum value in the ration is obtained.
These products come from the field at harvest time with a high population of natural micro-organisms that is variable in proportions of bacteria, yeasts and molds. As the plant becomes more mature, the proportion of yeasts (including spoilage yeasts) and molds increases.
Without the use of effective, research-proven inoculants as part of an overall good management program, these high-moisture corn grain products can readily become aerobically unstable during feedout due to an increase of the wild yeast population on the product when the silo is opened and exposed to oxygen.
High spoilage yeast populations can cause dramatic temperature increases (energy loss) and lead to significant spoilage.
When added to a lactating cow TMR, high levels of wild yeast can reduce DM intake and disrupt rumen function. The likely consequences are lowered rumen fiber digestion, reduced milkfat content and loss in average daily milk yield.
Key management steps to promote a successful ensiling process and feedout of high-moisture corn grain products are:
- Use of an effective, research-proven forage inoculant that contains a Lactobacillus buchneri strain that has received approval from the FDA for improved aerobic stability. The inclusion rate of the strain-specific L. buchneri must be targeted at 600,000 colony-forming units per gram of high-moisture corn grain product.
- Lining the inside of bunker walls with plastic prior to filling prevents water from seeping in at the edges. The result of this additional effort is that silage quality and DM along the wall is the same throughout the silo.
- Make sure the whole pile or bunker is covered and sealed as soon as possible, including the entire slope in front of the bunker or around the drive-over pile to prevent excessive spoilage in these areas.
Dual layer – black inner and white outer – thick (greater than 5 mil or 125 micron) plastic provides an effective cover and resists deterioration well. Effective oxygen-barrier films are much less permeable to oxygen than standard plastic and have been shown to reduce top spoilage.
- Design and use a silo to feed out at least 9 inches from the face daily. Pack tightly to remove all the oxygen, targeting a density of 45 pounds DM per cubic foot.
- Keep a smooth, clean face and avoid loose drop piles exposed to air for six hours or more.
- Minimize exposure to wind, dust or excess moisture (from rain or snow) by using excess plastic as a cover for the silo face.
Summary
There are a wide variety of high-moisture corn grain products in use on North American dairy farms. Each farm should have its own ensiled product analyzed regularly during feeding, as starch digestibility changes with length of storage time.
All these products share common characteristics: They require effective processing or grinding to get the full value of their starch content, and they are prone to be aerobically unstable at feedout and in the TMR, requiring best management practices at ensiling, including treatment with a research-proven L. buchneri inoculant at 600,000 colony-forming units per gram and excellent packing and sealing. 
Renato Schmidt is forage products specialist with Lallemand Animal Nutrition. Bob Charley is forage products manager at Lallemand Animal Nutrition.
References omitted but are available upon request. Click here to email an editor.
PHOTO: These are high-starch, high-value products intended to reduce the farm purchase of dry shell corn. However, they need attention to detail at ensiling and feedout to ensure the maximum value in the ration is obtained. Courtesy photo.
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Tony Hall
- Ruminant Technical Service
- Lallemand Animal Nutrition
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