Is a longer chop better?

Recently, there has been interest in the dairy industry of lengthening the theoretical length of cut (TLOC) of corn silage from its industry standard of 19 millimeters (mm) to a longer 26 mm cut (moving from ¾ to 1-inch).

“Farms feeding most of their forage as corn silage, desiring more physically effective fiber (peNDF) in the silage to displace dry hay or straw from the TMR (total mixed ration), have expressed the most interest,” Randy Shaver, professor at the University of Wisconsin-Madison, said at the 2018 Iowa-Wisconsin Silage Conference held in Dubuque, Iowa.

“People want to chop corn silage longer, but the longer the particle length, the harder it is to process the kernel,” the extension dairy specialist explained. He went on to suggest that a 40 to 50 percent speed differential between rolls has now improved kernel processing.

While modern processors with a greater roll speed differential are better able to create a longer particle size, is that really the best for cows?

The University of Wisconsin-Madison conducted a pair of feeding trials to compare different lengths of TLOC to the industry standard. There was no measured improvement in milkfat content or rumination time, which are indicators of peNDF.

Researchers from Italy, Cornell University, and the University of Pennsylvania School of Veterinary Medicine conducted a study on the length of particles following mastication or chewing during eating. They found that the length of particles entering the rumen had very little correlation with the feed particle length.

Forage particle length does influence eating time, but since particle size entering the rumen is rather uniform due to mastication, there is no effect on rumination (cud chewing) times or rumen fiber mat formation.

However, chopping forage particles to a length that is at or below the critical size for swallowing reduces eating and rumination times, which then reduces peNDF.

“More research is needed on longer chopping if the practice continues to be of interest to dairy managers and their consultants,” Shaver stated.

There are some potential downsides to a longer TLOC such as poor silo packing, more feed sorting, and reduced kernel processing. All three of these factors were measured in the University of Wisconsin-Madison study and were unaffected by the longer-chop treatment.

“Whether or not issues in these areas emerge for long chop silages most likely depends on silage and TMR moisture contents, harvest equipment type and setup, and management of the silo packing and TMR mixing and delivery processes,” Shaver explained.

Kassidy Buse

Kassidy Buse is serving as the 2018 Hay & Forage Grower summer editorial intern. She is from Bridgewater, S.D., and recently graduated from Iowa State University with a degree in animal science. Buse will be attending the University of Nebraska-Lincoln to pursue a master’s degree in ruminant nutrition this fall.