Processing Is Key to Feeding Light Test Weight Corn
Mar 08, 2010
Many areas of the Midwest are reporting light test weight corn and milo due to the delayed harvest. Light test weight grain is higher in crude protein, fiber and mineral content compared with normal test weight grain. Increases in concentration of these fractions come at the expense of reduced starch content.
Despite compositional differences, light test weight corn or milo is comparable in feeding value to normal grain in many situations. One challenge that must be overcome, however, is processing. Reduced kernel size makes processing light grain a challenge. Care must be taken to adjust rolls or flakers. Maintaining the feeding value of light grain is dependent on processing the grain well.
Fortunately, there is good, controlled research comparing rations containing light test weight versus normal weight corn and milo in growing and finishing cattle. North Dakota State University researchers compared grower diets containing normal dry-rolled corn with diets where 1⁄3, 2⁄3 or all of the corn was replaced with 39.1 lb./bu. corn. Dry matter intake and average daily gain were similar across all diets, and feed efficiency actually improved as light test weight corn increased. This may be due to the increased fiber content of light test weight grain, similar to fiber found in corn byproducts. Therefore, it is not surprising that feed efficiency improved in high-roughage grower diets containing light test weight corn.
Finishing diets. Research by the same group compared feeding normal corn, 47 lb./bu. corn and 39 lb./bu. corn in finishing diets with 81% dry-rolled corn. Finished weight and average daily gain were similar for all test weights. Dry matter intake in light corn diets increased in this trial, but other research shows similar intakes independent of test weight.
Unlike the growing trial, feed efficiency was reduced in finishing diets containing light test weight corn. Carcass quality grade does not appear to be dependent on test weight, but test weights below 47 lb./bu. may reduce ribeye size and increase yield grade.
Milo feed value. Research with milo in grower cattle limit-fed high-concentrate diets or full-fed high-roughage diets by Kansas State University determined light test weight milo had similar feeding value to normal grain. Finishing diet research found gain unaffected by bushel weight and feed efficiency were similar for all test weights if milo was dry-rolled, but was better for normal test weight milo if it was steam flaked. Dry-rolled milo diets require grain be processed well. Light test weight milo, characterized by small berries, can be difficult to process. Adjust rolls to prevent berries from going through the roller mill. Whole milo digestibility, particularly in high-concentrate diets, is poor.
The good news for cattle feeders is if you have homegrown light test weight grain, there is essentially no disadvantage in terms of feeding value. If you purchase light test weight grain, you may be able to buy the grain at a discount.
Available research shows light test weight grain will not affect performance or feed efficiency in growing rations. In finishing rations, similar performance can be expected, with a slight lack in feed efficiency. In either case, grain should be tested to account for increased protein and fiber components.
--Jeremy Martin is a ruminant nutritionist with Great Plains Livestock Consulting, Inc., located in Eagle, Neb. Visit www.GPLC-Inc.com.
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