Corn silage with very high dry matter (40-percent or more) decreased starch digestibility and milk yield, according to an extensive research review by University of Wisconsin dairy scientists.

Their summary shows milk production was not significantly affected when whole-plant dry matter stayed between 30 percent and 40 percent. However, much drier material (black layer and beyond) did cause a significant drop in both milk and fat-corrected milk production.

This is particularly true if you don’t do a good job of processing and chopping as the maturity of the corn silage increases, says Randy Shaver, University of Wisconsin extension dairy specialist.

“Keep that in mind if part of your strategy is to go for a drier corn silage to try to increase starch content,” he says.

The data showed no significant differences on the fat and protein content of milk. There also was no real evidence to show that a delayed harvest reduces neutral detergent fiber digestibility. If anything, Shaver says, the drier silage increased NDF digestibility. However, as the kernel becomes harder, there is a significant depression in total tract starch digestibility.

Shaver and graduate student Luiz Ferraretto examined two dozen published research papers, looking specifically at the effects of different corn silage harvest practices on parameters like milk production and dry matter intake. They reported these findings in July at the American Dairy Science Association’s annual meeting.