In most years, corn silage harvest starts in late August and early September for most producers. The reduction of growing degree day units and early frost will mean immature corn silage will be harvested in many locations leading to differences in silage quality compared to years with normal growth and development.

When evaluating corn silage quality, most producers consider protein and energy or starch content as the most important characteristics to determine the value of the crop. Immature harvested corn silage will have lower dry matter (DM) yield, starch and energy concentrations, and higher sugar, crude protein and neutral detergent fiber (NDF) concentrations as compared to mature corn silage. 

Dry matter yield and digestibility of immature corn silage are highest at the time of the first frost and additional losses occur as frosted corn remains in the field. This has led to reduced milk yields after repeated frost events. In addition, the corn silage might have higher effluent losses and extensive fermentation that could reduce dry matter intakes.

Changes in nutrient composition of corn silage with advancing maturity

Source: “Nutrient Requirements of Dairy Cattle, 2011”

To manage a frosted immature crop, several factors should be considered at harvest:

• Harvest at the correct DM content. Leaves will quickly turn brown and although the plant appears dry, whole plant DM will not decrease as quickly on a total plant basis. The majority of plant moisture will be found in the stalk and ear. Use whole plant DM to determine when to begin chopping and target moisture content between 32% to 38% DM.
• Harvest as quickly as possible. Increased drying of the plants usually occurs and delays may lead to silage that does not pack properly. Additionally, this will lower the risk of any molds that could grow on the ear while still in the field.
• Monitor silage particle size and kernel breakage. Cornell University recommends that there should be greater than 90% of kernels broken or damaged.
• Check each field prior to harvesting as different growing conditions from field to field and hybrid to hybrid will cause whole plant DM to change.
• Use of bacterial silage inoculant should be considered to improve fermentation efficiency and DM recovery. Frost will kill some of the normal bacteria found on the plant.

The best suggestion for producers when harvesting frosted corn silage is to use the basic principles that go hand in hand with good management practices.