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Good High Moisture Corn silage management benefits both farm and animals

Good High Moisture Corn silage management benefits both farm and animals

High moisture corn (HMC) has become a popular option for storing corn grain globally. It is defined as corn harvested at a moisture content above 24% (or below 76% Dry Matter content). Specific management practices are crucial to ensure optimal preservation and make the most of this type of forage for the herd’s performance and the farm’s bottom line.

High moisture corn in a nutshell

 Harvesting corn as HMC provides various advantages:

  • Reduced field losses compared to dry corn (reduced by up to 6%)
  • No drying charges
  • Flexible harvest window
  • Earlier stalk grazing
  • Energy is estimated to be 5 – 10% higher than dry corn

But there are also considerations to be aware of:

  • 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 chosen storage system 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
  • HMC is more prone to heating and aerobic yeast deterioration due to high starch content


When and how to harvest HMC?

Corn kernel moisture content (%)

(Bunkers / Piles / AgBags)

Minimum Desired Maximum

Ear Corn

(whole cob)

26% 32 – 36% 40%

Shelled Corn

(grain removed from cob)

26% 28 – 32% 36%
  • Moisture content (MC): Recommended MC levels are listed in the table above. Harvesting above 40% MC can lead to undesired yeast-driven fermentations.
  • Whole or shelled? Field inspection of the growing corn defines whether the corn can be shelled at point of harvest. If the growing corn is contaminated with field mold, harvesting as shelled corn may reduce, but not stop, the risk linked to mycotoxins by removing mycotoxins associated with the cob.
  • Maturity: Physiological maturity of the corn is dependent on the hybrid and the season, but it is shown by the formation of a black line at the base of the kernel –indicating maximum starch deposition
  • How to harvest? HMC is harvested differently depending on the exact nature of the final product. HMC and high moisture earn corn are harvested via combine, and snaplage with a snaplage header on a forager.


(%) High Moisture


High Moisture

Ear Corn

Corn 100 84 – 90 75 – 80
Cob 0 10 – 16 10 – 15
Husk, Shank, Leaf 0 0 5 – 10
 Crude Protein 9.5 9 8.5

To treat or not to treat?

Treating with silage additives helps reduce fermentation losses. HMC ferments more slowly and to a more limited level than corn silage, even though it contains higher relative amounts of starch. This high starch level, in turn, increases the risk of aerobic deterioration (undesired yeast fermentation in the presence of oxygen). HMC is thus more prone to heating. In this context, the use of Sil-All Maize+ is recommended to aid the preservation of HMC. First of all, it speeds up the fermentation by rapidly creating an anaerobic environment. It then increases aerobic stability thanks to the production of anti-fungal acids. Similarly, when the challenge is greater, or the farmer aims to feed out HMC rapidly, the use of Sil-All Fireguard will allow the rapid preservation and stability of the forage through the unique combination of fermentation drivers (bacteria), enzymes and anti-fungal chemicals that work in synergy to preserve and protect HMC rapidly.


Processing is achieved via rolling or grinding, and the degree to which processing occurs is dependent on the dry matter the intended storage method and the processing method.

  • Roller Mill: All kernels are broken into at least 4 pieces
  • Hammer Mills (Tub Grinder): Less than 5% whole kernels / less than 20% fines

If kernel moisture content is below 25%, the processing should be increased and water added to the grind in order to allow an effective fermentation (approximately 13 litres of water are required to increase by 1% the moisture content of 1T of HMC).

Excessive grinding can lead to higher levels of ‘fines,’ which have markedly faster digestibility and may increase acidosis risks for the animal.

There are distinct differences and advantages to the processing method that should be considered with regard to farm management and feeding systems. It is strongly advised that this is discussed with the farm nutritionist. Rolled HMC is simpler to manage than ground HMC as there is a lower level of fines, and rolled HMC generally leads to a higher DM intake and average daily gain, but feed efficiency is generally higher with ground HMC.


HMC can be stored equally well in bunkers and bags. What must always be kept in mind is to consider an appropriate silo face size to allow 10cm feedout per day, the recommended rate to avoid heating. If using bags, consideration should be given to the location of the bags, ensuring the bag is on hard ground and standing away from trees. Damage to the plastic during storage can lead to very high localized losses. Any punctures or rips should be immediately repaired.