Corn silage levels have been increasing in forage programs the past few years for a number of reasons. The volatile costs of corn and alfalfa hay, coupled with regional drought conditions and subsequent hay availability, have contributed greatly. Given these high corn silage rations now fed, it is no longer sufficient to rely on traditional testing for crude starch content of feed ingredients for ration formulation, especially when opening new crop corn silage.
Stop reacting to problems after they occur. Instead test silages to determine rumen degradable starch. Then use this information to proactively adjust ration formulation that will guide your cows to consistent, optimal performance.
Here’s what you need to know to get started.
Understand starch
Starch content and digestibility is highly variable. The amount of starch in corn silage can change from year to year based on hybrids selected, growing conditions and harvest management. For example, waiting for more ear fill before harvest may provide more total starch, but because that starch is more mature, it tends to be less degradable in the rumen at harvest. Understanding this inverse relationship between crude starch content and rumen degradable starch can help you make better corn silage harvest and ration decisions.
In addition, the longer the crop is ensiled, the more starch digestibility increases. That means the amount of rumen digestible starch available when you start feeding new corn silage can be significantly different from the amount of rumen digestible starch available by the time you reach the other end of the bunker.
Routinely testing corn silage for rumen degradable starch can alert you to changes occurring and prompt you to tweak the ration before cow performance suffers. When diets are not corrected for changes in rumen degradable starch, potential losses include a reduction in milk production, declines in the protein and butterfat content of milk and sometimes an increase in health issues.
Test every two weeks
Right before you start feeding new crop corn silage, test it for rumen degradable starch. (Old crop corn silage should also be tested on a routine basis to monitor variation in starch availability.)
NIR test results for rumen degradable starch are generally available within 48 hours once the samples reach the lab. These quick results allow you to formulate more precise rations because you have information on the availability and digestibility of starch.
Continue testing every two weeks. This will allow you to see changes in starch content and starch digestibility and correct the ration to avoid crashes. When it comes to consistent cow performance, it’s better to be proactive and prevent problems than to merely react to them.
Take action
Testing to determine rumen degradable starch gives you the ability to better control the cost of the ration and obtain more consistent performance from cows.
For example, a Wisconsin dairy was able to trim its feed cost by 20 cents per cow per day and improve the consistency of cow production by investing in starch digestibility testing. The dairy was feeding corn silage, snaplage and dried shell corn. Butterfat levels would crash when corn silage became fully fermented and then slowly recover.
Testing the ration for rumen degradable starch showed the herd’s nutritionist that he could remove all of the snaplage and most of the dried corn from the ration. But best of all, after the ration change, milk production still averaged 95 pounds of milk per cow per day, and butterfat held steady above 3.65 percent year-round, and protein held between 3.1 and 3.2 percent consistently.
Another benefit for this dairy was that it now had the opportunity to sell shelled corn previously used in the diet. The dairy continues to test rumen degradable starch every two weeks and before any new feed ingredient is introduced. Doing so has helped them keep this consistent performance going for four years.
The industry has learned a lot about rumen degradable starch in the last 10 years. Ration formulation today is much more science-based than ever before. Testing for rumen degradable starch gives you more insight into how cows will respond to a particular ingredient. That allows you to fine-tune or optimize the ration based on the feedstuffs available or even the cost of those feedstuffs. PD
David Weakley
Dairy Forage Research Director
Calibrate Technologies
