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Process Kernels to Improve Starch Digestibility, Maximize Production From Corn Silage


DES MOINES, Iowa.– Processed corn kernels in silage are readily digested, allowing cows to absorb more energy for milk production, say experts at Pioneer Hi-Bred, a DuPont business. Producers can improve starch digestibility in ruminants by adequately processing grains being fed and by thoroughly processing corn kernels during silage harvest.

“More than half of the digested energy in corn silage comes from the starch and sugar; and these come primarily from the corn kernel,” says Fred Owens, Pioneer senior research scientist. “Therefore, it is vital for producers to process corn silage to obtain high starch and energy availability.”

The smaller the kernel particles in corn silage, the more easily they are digested both in the rumen and intestines. Larger particles or whole kernels often pass through the tract undigested.

“Energy from feed becomes available only if the material is digested,” says Owens. “Whole kernels may pass through the digestive system intact. Sacrificing starch digestibility also sacrifices nutritional value and efficiency of production.”

Like starch in high moisture corn grain, starch from corn silage is digested primarily in the rumen. Although starch that is very rapidly digested in the rumen can cause acidosis, over-processing of grain included in the diet, not of the silage, and inadequate forage intake usually are the root causes of acidosis. Through increasing starch availability, kernel processing corn silage can reduce the amount of grain that needs to be fed.

“If a producer sees whole kernels or even half kernels in silage, digestibility of starch from that silage is less than ideal,” says Owens. “Chopping length at harvest has a limited impact on starch digestibility; gap setting on the kernel processing rolls is the primary driver. A gap setting of 1 mm for the processing rolls is considered ideal. To be well-digested, processed particles should be less than one-quarter of the size of the kernel.”

Corn silage that has not been kernel processed is another matter. For unprocessed corn silage or when the processor setting has allowed whole kernels to come through, kernel dry matter and kernel hardness can impact starch digestibility. Starch in unprocessed corn silage can have digestibility below 90 percent compared to more than 95 percent for processed silage.

Yet, compared with dry grain, grain in corn silage generally has high starch availability because of the fermentation process. Starch availability also increases during time in the silo. Corn silage several months old has higher feeding value than silage fed within a month after harvest.

“While it is recommended to stay within the suggested moisture bounds during corn silage harvest for ideal fermentation and compaction in storage structures, letting corn silage become a bit more mature certainly increases both starch content and silage yield,” says Owens. “But for more mature silage with drier grain, kernel processing of the silage during harvest becomes absolutely essential.”

Silage hybrids should be selected first for maturity and to match one’s agronomic practices. Then, because hybrids can have a large impact on yield and starch content, selection should be based on yield, tonnage, starch and fiber digestibility.

“If a producer sees whole kernels passing through cattle, kernel processing has failed,” says Owens. “Effectiveness of processing must be monitored during harvest. The only alternatives are reprocessing the silage at feeding time or delaying silage feeding until kernels have been softened by fermentation.”


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