High Moisture Corn Management
By: Jeremy Martin, Ph.D., Nutritionist
If putting up high moisture corn (HMC) is part of your repertoire, I am going to challenge you to manage the entire process in order to achieve success. From an agronomic standpoint, HMC expands the harvest season and reduces in-field grain loss by 3-6%. From a feeding standpoint, HMC improves both gain and conversion while typically resulting in less shrink than dry corn. While the benefits of HMC are apparent for both farming and feeding operations, success is in the details.
Most importantly, HMC must be stored at the right moisture level to maximize cattle performance. The ideal moisture range for harvesting HMC is 28-32% moisture, with maximum energy density and cattle performance between 30-31% moisture. Once the kernel reaches black layer, HMC harvest should begin in order to realize the most value. Timing is critical because by the time corn dries down to 23% moisture, it will feed with essentially the same energy as dry corn, but average energy value increases approximately 0.3% per point of moisture between 23 and 31%. Additionally, corn that is stored above 30% moisture becomes more digestible over time compared to corn stored at 24% moisture or less. In summary, ideal HMC harvest should start once black layer is achieved and be completed by the time corn has dried down to 28% moisture, resulting in an average moisture in the pile of 30-31%.
Every year, some corn is harvested for HMC below 26% moisture. When you expect that to happen, your process should be adjusted to gain more value out of drier corn. Our recommendation is to begin adding water when corn moisture drops below 28%, and focus on adding enough volume to bring the corn back to 30% moisture. In order to allow the corn to take in more moisture, it may be necessary to reduce the particle size of the grind. When corn drops below 23-24% moisture it is very difficult in most systems to reconstitute the corn to 30% moisture, and therefore we recommend a cutoff of 24% moisture for corn that is to be ensiled.
Particle size is the next critical point of HMC management. The correct particle size is very feedlot dependent, and is influenced by infrastructure, bunk management, and other available feedstuffs. Infrastructure is important, as it can limit the amount of HMC a feedlot can process in the ideal moisture window, and because the type of equipment present determines the best way to process corn. The ideal particle size at an operation will strike a balance between harvest efficiency, energy density, and the risk of digestive disturbances.
Feedlots that grind HMC with a hammer mill (tub grinder) generally create a finer grind that packs tighter, but ferments more quickly in the rumen resulting in greater risk of acidosis and bloat. Dry matter conversion of cattle fed hammer-milled HMC is usually better than those fed roller-milled HMC but dry matter intake and gain are usually lower. Monitoring particle size is important, with an achievable goal being no more than 3-4% whole kernels and not more than 20% fines (<1mm). Commercially available sieve shakers work well for determining particle size distribution, and should be used at least twice daily to determine if adjustments are needed.
Roller-milled HMC creates fewer fines, which result in lower risk of digestive deads along with increased dry matter intake and gain compared with hammer-milled corn. On the other hand, fewer fines mean roller-milled corn is more challenging to pack. Some manufacturers offer roller mills with differential drives on at least one set of rolls in order to create enough fine particles to assist in packing HMC. If milling HMC with a roller mill, strive for essentially no whole kernels and you should still be able to keep fines (<1mm) under 10%. In a perfect world, each kernel would be split into roughly 6 equal pieces. However, corn processed in such a manner does take more time to pack, so there is a time-saving advantage to creating more fines.
After moisture and processing, correctly packing HMC is next on the list. The goal is to remove all the oxygen or air pockets. In general, adequate packing requires a pack tractor for each 4-5,000 bushels per hour of grinding capacity. Pack tractors should not be sitting between loads, but constantly on the move. There is a fallacy that pushing corn up is enough during the day if you pack it well at the end of the day. The truth is, only the uppermost 6 inches of corn in the pile gets packed, so each load should be packed as it comes in. A well-packed HMC bunker will contain at least 45 lb of dry matter per cubic foot. Once packed, HMC should be covered immediately after completion of the pile to achieve the highest quality.
Another consideration for HMC production includes inoculants, which is a decision you should make in conjunction with your nutritionist, based on the cost of inoculation relative to the value of corn – and your ability to correctly apply inoculant. Also try to feed at least 6” off the face of the pile daily and maintain a vertical, flat face with no loose corn at the base of the pile to minimize shrink during feed-out.
With some planning and quality control, and some help from Mother Nature, you can put up a tremendous volume of HMC in a short period of time. Because the process needs to occur quickly, it is tempting to rush through processing and not focus on quality. This year, take the time to manage the process for a short period of time so you can enjoy the results throughout the rest of the year.
Dr. Jeremy Martin is a nutritionist with Great Plains Livestock Consulting, Inc. For more information, visit www.GPLC-Inc.com.