The main site of starch digestion is the rumen and processing can influence the extent of digestion in the rumen. Processing can increase rumen starch digestion from approximately 60% to 80%. This increase in ruminal starch fermentation can increase the risk of ruminal acidosis and digestive upset. Maintaining sufficient forage intake is important to reduce this risk. Today, the substitution of low starch feedstuffs like corn gluten and distillers grains for corn or other grains reduces the risk of digestive upsets.
I normally cannot convince producers that feeding whole corn rather than cracked corn will result in similar performance. Producers always have the rebuttal that they see whole kernels of corn in the feces. Research conducted by Ohio researchers investigated the interaction of grain processing and forage or roughage level in finishing diets. The poor student working on this project determined the number of corn kernels fed, and wait for it, physically separated corn kernels from the manure! For both weanlings and yearlings, the percentage of whole corn kernels digested was similar at 92%. The weanling calves ate almost 19,000 kernels of corn a day. Some quick math reveals that these steers excreted about 1,500 kernels of corn a day, about 1 pound of corn. Seeing this corn in the feces is the reason producers are convinced they must grind the corn. You are convinced now that you should process the corn, aren’t you?
This Ohio work also demonstrated that processing corn did not have an impact on digestibility of dry matter, starch, protein, or fiber. The authors mention a 44% increase in fecal starch excretion, a variable feedlot nutritionists monitor. This is a huge increase, right? Well, figures can be misleading and there was 100 grams more starch excreted in the feces. However, steers eating whole corn consumed 800 grams more starch compared to ground corn. Overall, total gastrointestinal tract starch digestibility was found to be similar at 93% for whole and 95% for ground corn. Previous research in Kansas revealed similar results with total GI tract digestibility of corn being 89% and 91%, whole and cracked, respectively.
What about performance on higher forage diets? North Dakota researchers investigated daily gains of yearling cattle from 900 to 1,100 lbs consuming a diet containing approximately 30% forage. Average daily gains for cattle receiving whole corn were 7% lower than cracked and 3% lower than ground corn. However, feed efficiency was better for whole corn. When 500-700 feeders were offered a receiving diet with 35% forage, gains were slightly higher for whole corn compared to cracked and gain efficiency was similar. These studies would seem to support the previous feedlot review with little or no benefit in processing corn.
In our area, cracked or ground corn is often significantly greater in price than whole corn. Further, if you can purchase whole corn from your neighbor at elevator price, it will often be much less than what one will pay from the feed dealer. In many instances, the cost of processing corn will likely not be recovered unless we are finishing cattle with low roughage diets.
I caution readers to consider the forage source and other diet components. If supplementing mature cows on the spring flush, the rapid passage rate and greater orifice for feed to pass out of the rumen will impact kernel digestion and processing corn will likely improve total tract digestibility greater than discussed above. Further, consider the risk of sorting. Cattle have the capacity to sort out larger feed particles, even the size of a corn gluten pellet. When using a loose mineral supplement or a protein source in a meal form like soybean meal or dried distillers grains, rolled corn may be needed to minimize sorting. This needs to be considered particularly if feed additives are in your mineral or meal protein source.
So, I ask you, process or feed whole?
Source : osu.edu