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Fast corn, slow corn, high priced corn

Jim Paulson

Published in Dairy Star February 4, 2011

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With the price of corn near or over $6.00 per bushel, anyone who feeds corn will want to maximize its value. Have you noticed any difference in feeding of the 2010 corn compared to other years or observed an unexplained lag in performance this year?

What determines how well corn performs in the lactation diet? Corn is fed to provide starch, which is an energy source. Starch digestibility is affected by particle size, moisture content, maturity, genetics, and fermentation. These are true whether it is corn grain or corn in corn silage. Animal factors include dry matter intake, rumen health, diet formulation, and diet ingredients.

Why and how do these factors affect the total digestibility of starch from the corn? Research at Ohio State University and Farmland Industries showed higher milk production from cows fed finer ground corn compared to cracked corn. Firkens et al. observed a ten unit increase in total tract digestibility of fine ground corn (700 micron; i.e. hog corn) compared to cracked corn. This would be approximately equal to saving 10 bushels of corn for every 3 tons of corn fed. This is also part of the reason for processing corn silage.

The genetics of corn affects many things such as the amount of oil, protein, protein type (high lysine for example), and type of endosperm: vitreous or floury. Higher test weight corn tends to have a greater vitreous portion as would popcorn and flinty corn. As the amount of vitreous endosperm increases, total digestibility decreases due to the starch protein matrix in the endosperm, especially the zein protein. Zein proteins, also known as prolamins, are not soluble in water or rumen fluid. Higher amounts of prolamins mean a greater protein matrix and greater inhibition of access to the starch in the endosperm. Hoffman and co-workers at the University of Wisconsin have developed a test to determine the Zein protein content of corn grain and help identify hybrids that will have lower vitreous content and thus higher digestibility. These tests are now available at many commercial labs.

Other things being equal like variety and grind, 30% moisture corn will digest faster and more completely than dry corn at 15% moisture. It has also been observed that some corn varieties digest faster than others even at the same moisture and grind. However, with high moisture corn that is fermented, the rate speeds up with longer fermentation. Eventually, all high moisture corn becomes fast digesting.

Fermentation, specifically the presence of lactic acid, breaks down the protein matrix in the corn endosperm or starch portion. This opens up the matrix and allows greater access by rumen microbes and enzymes in the small intestine, which leads to greater digestion.

Several animal related factors can affect the utilization of corn starch in the rumen. These include:

  1. the amount of dry matter intake. The more the animal eats, generally the less total time it will be in the rumen due to a higher turnover rate. The rate feed particles move out of the rumen is mainly due to size and density of the particle;
  2. higher producing cows tend eat more of higher quality feed, which is digested faster and moves out faster than a dry cow on poor quality hay;
  3. having a balanced ration with adequate fiber to maintain a good rumen mat will avoid sub-clinical acidosis and will slow rumen passage rate. This will also keep more corn grain in the rumen mat and not sink to the bottom;
  4. other sources of starch, sugars and carbohydrates can affect rumen pH as well as rumen buffers, forage to concentrate ratio levels, forage particle size, moisture level of the TMR, and sorting of the diet in the bunk.

So how do we apply all of this to make better use of our corn and increase profits? First, start with a check of the basics that have to be done anyway. Strive to feed all animals a consistent diet that is properly balanced for fiber, starch and other requirements. Beyond the basics, consider these things for the future if you are not doing them already:

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