High Moisture Corn (HMC) has become a popular option for storing maize grain globally for many reasons, its high energy silage, and it reduces the need and costs when drying grains. HMC can be described as corn grains harvested at a moisture content at between 28-32% and then processed by a roller or hammer mill.
Kernel processing is essential in realizing the benefits of HMC. It influences how much of this starch will be available in the rumen. The advantage of processing the kernel is that it breaks it open, therefore making the starch more accessible for rumen microbes. The higher the DM, the more critical it is to process the grain adequately, 70% of all grains should be less than 0.19 inch, or 4.75 mm. In a quarter gallon, or 1 L, of grain, less than three or four kernels should be unbroken or half-broken. Caution is advised when processing the grains as excessive grinding of HMC can lead the starch to break down to flour which have markedly faster digestibility and may lead to acidosis in the animal.
Although not desirable, it is possible to produce HMC, if the kernel moisture is lower than 25%. Water can be added to the grind helping ensure the fermentation is effective. Approximately 13 litres of water are required to increase 1T of HMC by 1% moisture content (e.g. from 25 to 26%). As there are distinct differences and advantages to the processing method, it is strongly advised that this is discussed with the farm nutritionist.
Benefits of HMC
The main advantages of harvesting corn as HMC formats are summarised below.
- Reduced field losses (reduced by up to 6%) compared to dry corn
- No drying charges
- Flexible harvest window
- Earlier stalk grazing
- Energy is estimated to be 5 – 10% higher than dry corn
Although not desirable, it is possible to produce HMC, If the kernel moisture is lower than 25%. Water can be added to the grind helping ensure the fermentation is effective. Approximately 13 litres of water are required to increase 1T of HMC by 1% moisture content (e.g. from 25 to 26%).
Treating and storing HMC
As HMC is a high energy moist crop, it should be treated with a forage inoculant, especially one designed to improve both preservation and aerobic spoilage. HMC can be stored equally well in bunkers and bags – but always with consideration to an appropriate ‘face size’ to allow a minimum of 10cm feed out per day. If using Agbags, consideration should be given to the location of the bags, ensuring the bag is on hard standing and away from trees. Damage to the plastic during storage can lead to very high localized losses. Any punctures/te should be repaired. For more information on storage options click here.
When feeding HMC there are a series of considerations the farm must recognize
- HMC ferments faster in the rumen than dry corn
- Digestibility of HMC significantly increases through storage which must be considered within the ongoing ration.
- The storage system adopted by the farm must be sized appropriately to the herd to allow a feed out rate of at least 10cm per day to avoid heating during warmer months
Feed out management of HMC is critical; it is is an excellent feed for both the animal and the spoilage organisms. Ideally, HMC should be shaved from the storage face but irrespective of feed out method loose material must be kept to a minimum.