Measure starch digestibility in corn silage to keep milk production up

SHOREVIEW, Minn. - Depending upon how much silage inventory carryover your farm has on hand, you may be looking at making the switch to new crop corn silage very soon, if you haven't already. When making this transition, it's important to keep a ...

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SHOREVIEW, Minn – Depending upon how much silage inventory carryover your farm has on hand, you may be looking at making the switch to new crop corn silage very soon, if you haven’t already. When making this transition, it’s important to keep a close eye on starch content and digestibility.


During corn silage storage, the total amount of starch in the pile will not change much (but it can vary throughout the pile). What does change, however, is the digestibility of the starch. Starch digestibility will increase as the ensiling time increases. 



“Starch digestibility is an important factor to consider because it directly impacts feed intake, milk production and component levels,” notes Margret Winsryg, Ph.D., customer service and technical support representative for Calibrate® Technologies. “When comparing various starch supplements, one must measure rumen digestible starch (RDS) and calculate what needs to be compensated for in the diet to optimize ruminal propionate production.”

Having too much or too little RDS can be problematic. An overabundance of starch, or starch with high digestibility, can cause production problems– lowered intakes, milk fat depression and milk production losses. Too little rumen digestible starch can result in low milk production.  Knowing the amount of RDS in the ration will ensure an optimal level to maintain milk production and rumen function.


When you first open new corn silage, the amount of RDS will typically fall below a cow’s dietary needs. But as time passes, starch digestibility can increase. If you first open your corn silage in November, feeding the same amount in February may provide more rumen digestible starch because the feed’s degradability and RDS level have increased during storage. As a result, you may need to exchange some of the corn silage for alternative forages containing less starch or lower ruminal starch digestion by replacing grain sources with high fiber byproducts to maintain milk components. 


“When making any decisions on what crops to feed or supplement, make sure you carefully consider starch requirements first, so you don’t compromise dietary success,” warnsWinsryg. 


So what can help you determine if the RDS level of your ration is consistent as you feed out your silage supply? A starch digestibility test is just the answer.



There are a number of ways to test for starch digestibility. Regardless of the method used, what is most important is that the results are accurate, rapid and can easily be applied to the ration formulation.


Monitoring RDS levels year-round on an every-other-week basis can help you and your nutritionist determine how much starch is available in the ration. By knowing the starch content and digestibility, it allows you to optimize ingredients and milk production while potentially reducing ration cost. A starch digestibility test can provide precise results that will help fill the gap in the ration and ensure optimal RDS levels are maintained during feed out of corn silage. 

Do you want to ensure your RDS level is maintained in your ration when adding starch supplements? Call:  (800) 635-5701 , email:  or go to:  to receive more information on forage quality tests.  

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