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Utilizing light test weight corn

Mike Boersma

The 2013 harvest season is winding down.  According to the November 4th USDA Crop and Weather Report, 73% of Minnesota’s corn had been harvested by November 3rd.  This is actually on track with the 5-year average of 72%.  While corn and soybean yields were generally good in southern Minnesota, producers likely noticed some lighter test weights during corn harvest.  Corn test weight is considered “normal” at 56 pounds per bushel (a bushel is equal to 1.24 cubic feet).  Lighter test weights- in the lower 50’s-were common this fall.
Light test weight corn is the result of kernels not maturing properly.  This can be due to a cooler than normal growing season, drought stress, an early frost, or any other factor that prevents the plant from maturing fully.  These factors cause corn to have lower starch content than corn of normal weight.  The lower starch values often lead to corn that is also lower in energy. 

However, even with the lower energy values, numerous studies have shown no negative effects of light test weight corn on animal performance, as long as the test weights are not severely low (below about 45 lb/bushel).  In fact, some would even argue that light test weight corn has a higher feeding value than normal corn due to its slightly higher fat, fiber, and mineral concentrations.

So, livestock producers may serve as a good market for light test weight corn that would otherwise be penalized at the elevator.  If livestock producers plan to utilize light weight corn, here are a few points to keep in mind.

First, light test weight corn weighs less per unit of volume so it is increasingly important that producers use scales and accurately weigh the corn when mixing feed.  If corn is measured on volume alone and inclusion rates are not adjusted for the light test weight, corn would be underfed and the actual energy content of the diet would likely be less than anticipated.  There was some variation in corn test weights this year and this could cause variability in diet energy concentration if mixing on volume alone.  Using scales to weigh ingredients and using a constant blend of corn will help reduce variation of the finished diet.

Livestock producers should also be sure to evaluate the corn they are feeding.  Protein values can be somewhat variable in light test weight grains so it is more important to have corn tested.  Also, light test weight grain has a greater likelihood of being damaged and developing mold during storage.  While these challenges can often be overcome with good management, it is important to know about potential challenges in advance so they can be managed accordingly.  If these points are kept in mind, utilizing light weight corn in livestock feed can be a very viable option.

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