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Silage Management: Steps to Tackle Shrinking

26 August 2014

Minimise corn silage shrink by chopping finely, rapid filling and sealing securely, Karla Hernandez, forages specialist at South Dakota State University has advised.

This is the time of the year that we need to be thinking about how to manage and minimize corn silage shrink losses.

Karla Hernandez: Less than 30 per cent dry matter results in low starch which is the risk of early harvesting.

Stored silage can provide quality feed to support many different livestock systems. Corn silage is a major ingredient in most dairy rations in the United States.

Corn for silage should typically be harvested between 60-70 per cent moisture to ensure good storage and fermentation.

One of the main characteristics of corn silage is that it is well-suited to preserve forage at an optimum harvest stage that maximizes energy content.


Corn silage ferments best at a pH of near 4.0

Adequate moisture content allows for good fermentation which resulting in a rapid pH drops to near 4.0, which is characteristic of well-preserved corn silage.

A very basic estimate of whole plant moisture for harvest can be made using the kernel milk line. The kernel milk line is the dividing line between sugars in the maturing kernel and starch deposited.

Most producers in South Dakota will use the 1/3 milk line as the point to start checking whole plant moisture to determine the optimum timing for silage harvest. On the other hand, maximizing the nutritional quality of corn silage and minimizing shrink losses are two main factors to take into consideration when feeding livestock.

Therefore, harvesting corn silage too early at less than 30 per cent dry matter (DM) will result in lower starch concentration in the silage. However, mature corn silage (silage with more than 38 per cent DM) could also have less nutritional value because of lower fiber and starch digestibility.

Factors Affecting Shrink Losses

Some of the factors that affect shrink losses are the following:

  1. Type of structure: Bunkers usually have the greatest shrink when compared to other types of storage structures.
  2. Chop length: Finely chopped forages are better and lead to increase silage density. Overall, corn silage should be chopped very fine (1/4 in to 3/8 in).
  3. Rate of filling: Slow filling will reduce the rate of fermentation so that pH stays higher for longer time. Some of the problems with shrink losses are the air trapped inside the silage. This will promote yeasts and mold causing serious problems to the final product.
  4. Covering the silage: Covering a bunker with plastic is the best choice to reduce shrink losses. For better results cover quickly after the bunker has been filled.


Stored silage can provide high quality forage needed to support livestock systems. Pay attention to maturity stage, and leaf/stem ratio. Maximize nutritional value of corn silage by chopping corn when is between 30-38 per cent DM. Shrink losses are usually minimized by chopping fine enough, filling rapidly, packing, and an adequate and fast sealing with an air-tight cover.

Collins M and Owens V (2002) Hay and silage preservation. In R.F. Barnes, C.J. Nelson, M. Collins, and K. Moore (eds.), Forages: The Science of Grassland Agriculture, vol. 2. Ames, Iowa: Iowa State Univ. Press. P: 443-469.
Hinen J (2006) The big 6- Focus on the 6 keys to quality corn silage. Mid-South Ruminant Nutrition Conference. P: 1-10.

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