Growing Beef Newsletter
October 2025, Volume 16, Issue 4
Got some light test weight corn? Feed it!
Patrick Wall, ISUEO area beef field specialist
Every growing season has its challenges, and 2025 was no different. Though there will likely be an abundance of feedstuffs to offer the depleted US cow herd, digging into some specific issues could offer you an advantage…or at least an alternative to the challenge. The onset of Southern Rust in a good bit of Iowa’s corn acres certainly offered a new challenge for this fall. While yield drag appears to be the main result, some instances have reported lighter test weights than ideal. This article will focus on opportunities to feed that crop to cattle rather than selling it by the pound.
The first challenge might be separating the light test weight grain from the ‘heavy’ stuff. Blending rations when corn of varying test weights is in the mix could prove challenging. If it can be kept in a separate bin for instance, the first step is to test it for nutrient value, particularly for protein and fiber. In general, light test weight corn is higher in protein and fiber, but lower in energy. However, there have been some instances where light test weight corn has shown comparable or even slightly high net energy values. All that said, knowing what you have for your particular sample will be beneficial when incorporating it into a diet. It would also be a good idea to test and monitor that corn for molds and mycotoxins.
The next step is to determine where that feed works best. Research suggests light test weight corn fits better in weaned calf diets than finishing rations. Calves typically see an increase in performance, which logically makes sense given the increase in protein and fiber demanded by calves. If the volume of the light test weight corn exceeds what you need for calf diets, it can still be utilized in finishing diets. Most trials noted similar gain/performance, but a slight decrease in feed efficiency. Not all research agrees 100% on best utilization, likely due to the variation in nutrient profile of light test weight corn. North Dakota State University found corn as low as 40.8 lbs./bu in a trial; University of Nebraska-Lincoln classified light test weight corn at 56 lbs./bu. Again, testing your sample for nutrient profile is critical in telling you how to best utilize it.
Even with significant disease pressure and yield drag across Iowa, the state is still set to likely produce its largest corn crop ever. At the same time, cattle producers are marketing the highest priced feeder calves, fed cattle, and even cull cows in recorded history. Anything producers can do to add pounds to cattle is certainly profitable. Marketing discounted grain through record-high beef is a no-brainer!
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