As corn silage season fast approaches, it is important for dairy farmers to consider how to maximize its nutritional value to their herds.

Rather than using a combine to harvest dry kernels of corn, harvesting corn silage is quite different. When harvesting corn silage, a chopper is used in the fields instead.

According to Dr. Luiz Ferraretto, an assistant professor and Extension specialist focusing on ruminant nutrition at the University of Wisconsin – Madison, just how a farmer processes that harvest can have a profound effect on their dairy herd.

Corn silage processing can be done with a processor mounted on the forage harvester or by a stationary roller mill, normally located at or near the silo where it will be stored. The more frequently used system is having the processor attached to the forage chopper. The processor unit is made up of two counter-rotating rolls positioned between the cutter head and blower. This results in the crushing of the grain as well as the crushing and shearing of the cob and stem.

The feed is also a seed

Dr. Luiz Ferraretto

Ferraretto said, “It’s key to remember that the feed is also a seed.” He explained that corn kernels are themselves seeds, and like all seeds, the inner space is contained within a protective outer layer. The endosperm, which contains the starch content of the kernel, is surrounded by the outer wall called the pericarp.

“A healthy diet for dairy cows should be about 25% starch,” he said. “So if we can maximize the amount of starch the cows absorb from the corn silage, we can help farmers improve their herds’ diets while keeping feed costs down.”

Starchy foods are the main source of carbohydrates and play an important role in any animal’s healthy diet. They are also a good source of energy and the main source of a range of nutrients. As well as starch, they contain fiber, calcium, iron and B vitamins.

Ferraretto described research which recorded the rate of starch absorption from corn silage broken up into various sizes. The rates of starch absorption were determined by observing the amount of starch that passed through the cows and expelled with their fecal matter.

The corn kernels were fed to cows whole as well as broken up into 1/2, 1/4, 1/8, 1/16, 1/32 and 1/64 size pieces. In short, the smaller the pieces the kernels were broken up into, the better.

“Whole kernels proved largely indigestible and most of their starch content passed through into the manure,” Ferraretto said.

He said that while he doubts grinding up the kernels into a full powder might not be practical, he believes that breaking down the kernels into smaller pieces will save farmers money.

“If you feed low digestibility diets, in terms of fiber, cows will have between 5% and 15% lower intake and they will spend 5% to 20% more time in the feed bunk,” he said.

by Enrico Villamaino