'Within five years, almost every forage harvester will have a crop processor," Kevin Shinners predicts.

Shinners, a University of Wisconsin ag engineer, is enthusiastic about this latest wrinkle in corn silage production, and he's not alone. Growing numbers of dairy farmers are finding that running chopped corn through processing rolls can put more milk in the tank.

The benefits come from increased silage digestibility. Often called kernel processing, crop processing actually works on the whole plant, says Shinners. Besides damaging the kernels so they don't pass through animals undigested, it breaks up cob pieces, making them easier to digest and preventing separation in the feedbunk. It also damages stalk pieces, perhaps making them more digestible, too.

However, farmers need to pay attention to certain machine adjustments, as well as to crop maturity, in order to get the desired results, says Shinners.

He and his colleagues harvested corn silage with a kernel processor the last two falls, comparing several equipment settings and corn-crop maturities. Their recommendations:

* Increase the forage harvester's theoretical length of cut to 3/4". The coarse silage may improve rumen health, and the crop processor will break up the big cob pieces that otherwise would result.

Don't cut longer than 3/4", however. Coarser material could cause excessive wear on the processor, and may not pack well in the silo.

* Set the processing roll clearance at 3 mm.

"Also, if a custom harvester is doing your work, be diligent and work with him to set the clearance on the machine correctly to make sure you're getting the end product that you want," Shinners advises.

In the research, the 3-mm clearance resulted in 3% undamaged kernels, compared with 12% undamaged kernels for the 5-mm clearance. Virtually all kernels were damaged with the 1-mm clearance.

"We think it doesn't pay to have a kernel processor and leave 12% of the kernels undamaged. But 1 mm may be a little too aggressive, and it takes more power."

He adds: "If you operate the machine at 3/4" length of cut and a 3-mm clearance, you'll have about the same horsepower requirement and about the same throughput as if you were cutting without the processor at 3/8" length of cut."

* If you set the rolls at 1-3 mm clearance when chopping at early dent, you may not have to change the clearance as the crop matures. Some farmers think they need to reduce the processing roll clearance as the corn ripens. But the Wisconsin researchers found that to be unnecessary.

* Don't delay harvest beyond the 1/2 kernel milkline stage of maturity, as sometimes is recommended for silage processing.

"As the crop matures, stalk lignin and fiber levels increase, and starch binds with protein in the ears. The processor can't do much about it," says Shinners.

Currently, crop processors are optional on all self-propelled forage harvesters and several pull-type models. In addition, at least two companies sell retrofit crop processor kits for pull-type machines.