Frost Damaged and Immature Corn Options

For farmers who experience a cool, wet spring, a wet fall and early frost, there are some options for immature or damaged crops. For livestock producers, damaged crops can have great benefits in producing high quality feed options. These options include silage, harvesting high moisture grain or grazing to name a few. 

Silage Basics

When it comes to silage, timing of harvest is one of the most critical factors affecting quality. For maximum quality, it should be harvested at 55 to 68 per cent plant moisture. In most years, early planting allows for proper timing in the fall before freezing occurs.
However, when immaturity and frost affect the plant, here are some considerations to ensure a quality feed is harvested. The ideal maturity timing for harvest of corn silage is 1/3 to 2/3 milk line in the kernels to achieve highest quality.

Effect of Frost and Immaturity

In most cases, immediately after a frost, the immature corn will be too high in moisture to chop. When possible, chopping should be delayed until the plant is dried down to 55 to 68 per cent moisture. 
Harvesting silage at too high of moisture will alter the fermentation process, increase seepage losses and can potentially decrease feed intake. It can also cause problems with the pile freezing in the frigid winter temperatures.
To avoid these losses, it is necessary to allow the crop to stand in the field and dry down to adequate moisture levels. Determining the moisture level of a crop after a frost can be tricky. The frosted leaves can turn brown and give the appearance that the whole plant is dry. However, most of the moisture is in the stalk and ear of the plant causing the total plant moisture to be significantly higher than it appears. 
Remember, frozen immature corn will not dry down any faster than unfrozen corn. As a rule, whole plant moisture only decreases by 0.5 per cent, per day. Silage management practices are critical to storing immature or frozen corn silage. Packing, covering and particle size guidelines used in harvesting normal corn silage should be followed for immature or frozen corn as well. 
Under good conditions, preservatives and inoculants are generally not necessary; however, this may be a situation to consider their use as the frost may kill some of the naturally occurring fermentation bacteria on the plants. Be sure to use research-proven inoculants and follow the manufacturer’s directions.

Feed Quality Considerations

It’s not surprising that the feed quantity and quality of frosted, immature corn depends on the stage of maturity at the time of harvest.
Immature corn at the dough stage can yield anywhere from 65 to 85 per cent of normal tonnage. Slightly immature frosted corn that had dented can still make good quality silage with only slightly lower yields. The energy is partitioned differently in immature corn than in normal corn silage. The kernels have lower starch content but the stalks have a higher sugar and lower lignin content, making the stalks potentially more digestible.
In general, immature corn will have slightly higher fibre and crude protein levels but will have slightly lower energy levels than normal silage. After a frost, if the leaf is dead but the stalks and roots remain alive, there is the risk of nitrates accumulating in the lower stalk. Increasing cutting height will lower the dry matter but increase silage quality since the lower stalk has the lowest digestibility and highest nitrate levels. However, this can also reduce the yield by about 15 per cent.
Table 1. Corn silage quality at different harvest maturities
Stage of Maturity
Crude Protein
--------------- % Dry Matter ---------------
Soft Dough
Early Dent
½ Milk Line
¾ Milk Line
No Milk Line
Adapted from Wiersma, D.W, P.R. Carter, K.A. Albrecht and J.G. Coors. 1993. J. Pord. Agric. Vol. 6, no. 1, p. 94-99.
1Nutral Detergent Fibre
2Acid Detergent Fibre

Feed Test

It is always a good practice to have a feed analysis done on feeds in unique situations like this. Ensure proper sampling techniques to produce a representative sample to have the most accurate results possible. This would be by using a feed probe, sampling 15 to 20 spots on the face of the pile. When selecting your analysis, ensure a pH test be included to ensure ensiling has completed properly. Consult with a nutritionist when balancing rations.