As corn planters are finally starting to roll in the Midwest, planning for the finished product can never start too early. Corn silage is the most commonly used forage in dairy rations and the inclusion rates are continuing to increase. One of the main reasons for the increase in inclusion rates is the ability to manage starch digestibility. Decisions made at harvest can impact starch content and future starch digestibility of the corn silage crop.
Harvest at proper maturity
Starch content is impacted by harvest maturity. Starch can increase by 25% from harvesting at black layer maturity rather than ½ milk line. However, waiting for kernel maturity will also impact dry matter of the forage. Harvesting corn silage at ¾ milk line and dry matter percent of 35 to 38% will allow for higher starch content while reaching proper dry matter for silage storage. Waiting for the corn to become too mature can lower the digestibility of the starch because it passes through the rumen too quickly. Kernel processing drier corn can make the starch more easily available in the rumen.
Use a kernel processor
The use of a kernel processor at harvest will also make starch more readily available. Most choppers now come equipped with a kernel processor, but chopper settings can impact processing performance. Make sure roller mills are properly maintenanced before fall chopping. Gap settings should be spaced at 1 to 3 mm. The speed and timing of the roller mills should also be considered. During harvest, collect a 32oz cup of silage at harvest to determine if the kernels are adequately processed. No more than 2 whole kernels should be found in the 32oz cup of silage.
Consider storage time
The length of time you can store silage before use will affect the starch digestibility of the silage. Rumen digestibility of starch is about 70% at 7 hours. The seven-hour digestibility continues to increase by about 2% per month. Research has shown that rumen starch digestibility can take anywhere between 6 and 8 months to peak. Work closely with a nutritionist to determine how starch digestibility may change throughout the year.
Starch content can range from 20% to 35% of the dairy ration. Most of the starch comes from grains which add more cost to the ration. Fewer grains can be used when starch content of corn silage is utilized. Timing of harvest will impact starch content while storage time and use of a kernel processor will impact starch digestibility.
