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Hard corn kernels stunt cows’ starch use

Maggie Gilles, Kansas Dairy Farmer


December 9, 2021



As the year comes to an end, many dairy farmers have or are beginning to open 2021 silage storage and finding that it’s not feeding as well as some other years despite mostly having good fiber digestibility and starch levels. During the December 8 Hoard’s Dairyman DairyLivestream, panelists discussed the 2021 harvest and resulting hard-shelled corn that might be stunting starch digestibility in rations across the country.


“We’re seeing a little bit less in rumen starch digestibility – actually quite a bit less in rumen starch digestibility,” explained Rock River Laboratory’s John Goeser while discussing lab results of 2021 harvested corn silage. “We have decent yields, but our grain component — despite decent starch levels in this year’s silage — really doesn’t look like we’re going to be capturing full potential as soon as we might have in prior years.”


Is this happening on your farm?


The concern surrounding starch digestibility and wasted energy in the ration has led dairies to ask the question, “How can we know if we’re dealing with this problem?” In terms of identifying the issue, Goeser says two laboratory run tests — seven-hour starch digestibility and fecal starch levels — can offer a farm a good starting point in understanding that operation’s specific starch utilization.


“Commercial laboratories have developed lab-bench or rumen incubation protocols so we can get an idea of rumen starch digestibility with our corn silages. There are a little bit different protocols depending upon the laboratory, but we’re giving out numbers that will index starch digestibility,” he explained. “What we recognize with corn silages is that we will range anywhere from 60% to upwards of 95% in rumen starch digestibility.”

This test describes roughly the starch digestibility a farm can expect from its corn silage as it passes through the digestive tract. Goeser and fellow panelist Mike Hutjens, who is a professor emeritus at the University of Illinois, shared that this value may be several points lower than other years.


The second test that can help benchmark lost starch value is fecal starch values. This test looks specifically at the amount of starch that passed through the cow undigested and into manure.


“There is some unfortunate value in a lot of manure. I would start by looking at fecal starch on-farm,” Goeser said.


Hutjens echoed this recommendation.


“You can see that if your fecal starch is up at 6%, which is a pretty high number for dairy cattle,” the storied dairy nutritionist explained. “You can figure out that if you’re missing four or so points, you’re missing 2 or 3 pounds of milk, which is going to be equal to a pound or a pound and a half of corn.”


If this excess fecal starch is the result of the corn silage, Hutjens and Goeser recommended allowing as much fermentation as possible in the silo. If that’s not possible, adding corn grain might be necessary. If the excess can be associated with ground corn inclusion, the pair strongly recommended looking at grinding level and further hammering down the particle size to aid fermentation in the rumen.


To watch the recording of the December 8 DairyLivestream, go to the link above. The program recording is now also available as an audio-only podcast on Apple Podcasts, Spotify, Google Podcasts, and downloadable from the Hoard’s Dairyman website.


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