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Feeding Value of Light-Test Weight Corn

02 October 2012

US - As the 2012 growing season winds to a close and the final harvest results start to come in, one of the concerns is the possibility of lower test weights for the corn crop. The stress that the corn crop was under due to the drought conditions this year could certainly result in test weights that are lower than normal in some places. So how does reduced test weight affect the feeding value of corn and cattle performance?

On the surface it would seem very logical that lowered test weight would mean that the feed is less valuable as a feedstuff. Lower test weight in corn means that there are fewer pounds of grain in a given volume. So it stands to reason that reduced bulk density also means poorer cattle performance and efficiency. But it’s important to compare our assumptions with research data to see if those assumptions are valid.

Research from South Dakota State University would suggest that those assumptions don’t hold water. In a metabolism trial using cattle, researchers determined that energy values for corn with a test weight of 41 pounds were no different than energy values for corn with a test weight of 54 pounds. Trials in Nebraska with growing and finishing cattle showed similar results. In that research, cattle fed corn with a 47 pound test weight showed similar growth rates and efficiencies compared to cattle fed diets based on 56 # corn.

How can cattle feeders use that knowledge? For cattle feeders that also grow corn, this may represent an opportunity to capture more value from the corn crop. Typically there is a discount in the market place for lower test weight corn. Based on the published data, these discounts aren’t justified, at least based on the grains’ ability to support cattle performance. There may be an opportunity to sell corn that is higher in test weight, and hang on to the lighter test weight corn for cattle feed, and thereby avoid or lessen discounts in the corn market. For cattle feeders that need to purchase corn, these findings might represent a way to reduce feed costs. For either group of cattle feeders, this could represent a chance to exploit price differences in feedstuffs without compromising cattle performance.

Another consideration to keep in mind is crude protein concentrations. Given the current value of gain in cattle and the high cost of providing supplemental protein, both over- and under-feeding protein can be a costly mistake. Drought stressed corn can be quite variable in crude protein content, but is often higher than what we might find in normal corn. Spending a few extra dollars to determine the exact protein levels could save a tremendous amount in either lower supplement costs or by avoiding lags in cattle performance.

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