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Dairy cows need corn harvested at right moisture

Dairy cows perform best when the corn they're fed is harvested at the proper moisture level.

While the corn silage harvest may be a ways off in North Dakota, it is getting under way in the eastern portion of the U.S.

Therefore, this is not too soon to be thinking about staging for ensiling corn, especially for dairy farms. Corn silage makes up a significant portion of the dairy rations. Given the price outlook for corn, many will be looking for ways to decrease the amount of corn in the diet or get more out of that expensive input.

The first place to start is getting the moisture right to achieve higher milk yields per ton of silage fed.

University of Wisconsin researchers lead the way in getting the corn right for the cow. Their dairy farms repeatedly have demonstrated the advantages of harvesting corn silage at the recommended whole-plant moistures. Dairy cows perform best when whole-plant moistures are in the 60 to 75 percent range at harvest.

That range also works well for achieving food packing and fermentation in the horizontal silos. Increased seepage losses, increased acidity and lower dry-matter intakes are common problems when whole-plant moisture is greater than 70 percent.

If storing in upright silos, plan for whole-plant moistures in the 62 to 65 percent range. Corn silage harvested at 60 percent moisture or less consistently results in reduced fiber and starch digestibility.

Take note of when corn fields targeted for silage harvest are silking. The silage harvest usually begins 42 to 47 days after silking, or at approximately 50 percent kernel milk. However, kernel milk is not a good indicator of whole-plant moisture. I recommend sampling plants from the field and testing for moisture to determine whole-plant moisture accurately. Hybrids, soil moisture, soil fertility, weed control and sample location in the field all impact the whole-plant moisture and dry-down rate.

Ideally, fields to be harvested would be uniform, but this rarely is the situation. Research conducted at the University of Wisconsin Research Farm at Arlington in 2003 found that knoll areas of the field were as much as 20 percent drier than lower areas of the field. Keep in mind, significant rainfall events will rehydrate moisture-stressed corn plants by as much as 6 to 8 percent within a day or two.

Mike Ballweg, the University of Wisconsin Extension’s Sheboygan County crops and soils agent, offers these sampling recommendations:

  • Sample two or more locations for each representative area in the field. If sampling more than once, sample the same locations to determine the rate of dry down.
  • Sample three to five plants in a row. These plants should be well-bordered and representative.
  • Chop the samples as quickly as possible and put them in a plastic bag.
  • Use near-infrared spectroscopy for the most accurate moisture results. When using a Koster oven or microwave, add 2 to 4 percent moisture onto test results to account for residual moisture.

Use 0.5 percent per day as an average dry-down rate during September. Depending on the year, the average dry-down rates for September range from 0.4 to 0.7 percent per day. On the other hand, daily dry-down rates during September can vary greatly from near 0 percent per day to as much as 1 percent per day.

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