Strategies for High Fiber and Starch Digestibility

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Homegrown forage is the most important feed ingredient available due to a producer’s ability to control quality and be 100% sure what he or she is feeding. It’s also cheaper and typically higher quality than purchased forages.

“Doing everything you can to improve the quality of homegrown forage, and therefore silage digestibility, is incredibly valuable to your operation,” said Luiz Ferraretto, assistant professor in the Department of Animal Sciences, University of Florida.

Silage digestibility is important for two reasons: fiber digestibility and starch digestibility. The more digestible the fiber, the faster it will be digested in the rumen. Consequently, cows will be able to consume more feed, which means they will have greater energy.

“From a starch digestibility perspective, you have greater levels of energy available when your silage is more digestible,” he said. “Higher energy allows cows to produce more milk or, alternatively, produce the same amount of milk while consuming less food.”

There are three management strategies to improve fiber digestibility:

  1. Select hybrids of greater digestibility – brown midrib hybrids are an example
  2. Monitor harvest timing – maturity influences fiber digestibility in corn plants
  3. Increase cutting height – increased height decreases the level of lignin in the harvested plant since most of the lignin is located in the bottom part of the plant; fiber becomes more available and, consequently, more digestible

To improve starch digestibility, breaking kernels is the most important factor. If you don’t break kernels up enough, the rumen material or enzymes in the intestine will not be able to access the starch, Ferraretto said.

After the kernel is broken into many pieces, there are two additional factors that contribute to starch digestibility:

  1. Harvest timing – from a grain perspective, a later maturity will be less digestible in the rumen
  2. Length of fermentation – over time, bacteria in the silo will break down protein that surrounds starch, making it more available in the rumen

The greatest increase in starch digestibility is during the initial three to four months of storage. Digestibility continues to increase the longer you continue the fermentation process, but the magnitude of those changes becomes smaller.

“There is a farm here in Florida that stores silage for a whole year prior to feeding, and other farms in the Midwest are adopting four to six months of fermentation,” Ferraretto said. “Plan to have enough area or inventory available the first year you implement a longer fermentation on-farm. It requires a higher investment, as you need to have more silage to harvest so you can account for the extra inventory.”

If planning to increase length of fermentation, it’s also important your silage be well packed and sealed and treated with a microbial inoculant to safeguard your investment.

“Highly digestible hybrids are also important, but consider using only hybrids that are consistent throughout the years,” Ferraretto noted. “Some may not be the most digestible, but they are consistently very good in digestibility and consistently have very high yields. Those are the hybrids you want to plant; they can limit variation that may compromise either inventory or quality.”


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