Determining the physical effectiveness factor (pef) of forages will soon be easier for dairy producers and nutritionists who use ration balancing programs that require effective fiber data.

An easy on-farm method that uses wet forages has been developed by the research staff of the Miner Agricultural Research Institute, Chazy, NY. It's designed as an alternative to the commonly used Ro-Tap Sieve Shaker method, which requires dry forage samples.

“We needed a simpler system,” says Kurt Cotanch, who is the institute's forage lab director. “Until now, a tool to measure on-farm pef did not exist, and that's what we think we have here.”

The research was funded by Zen-Noh, a group of ag co-ops in Japan, where the CPM-Dairy ration balancing program is popular. That program, also widely used in the U.S., requires physically effective NDF (peNDF) as an input.

The new method centers around a box, called the Z-Box, which separates forage particles by length much like the Penn State Forage Particle Separator does. But this one utilizes only one screen and comes up with a single value, the pef. That number is then multiplied by the forage's lab-test NDF to get its peNDF.

The box has one removable perforated-steel screen for corn silage and one for hay-crop silage. The user places a small forage sample (50-70 grams) in the box, adds the appropriate screen, snaps on a lid and weighs the filled box. Then he shakes it vigorously using vertical motion and rotating the box similar to the Penn State box method.

Short forage particles fall through the screen and out of the box. The box then is reweighed, and the percentage of particles retained is the pef. If 50 grams of forage are reduced to 40 grams, for example, the pef is 80%. The procedure is done twice more to ensure accuracy.

“It only takes 30 seconds to do,” says Cotanch. “We do three reps so we're sure we get a good, representative sample of the forage or TMR we're testing.”

The research started with the premise, from earlier studies at the U.S. Dairy Forage Research Center, that dry feed particles must be at least 1.18 mm long to maintain proper rumen pH. But particles shrink when dried, so Cotanch and institute president Rick Grant had to identify the wet, or as-fed, particle lengths that correspond to the 1.18-mm dry forage benchmark.

They sieved several forage samples through a variety of hole sizes, in each case comparing their findings with results from the Ro-Tap dry sieving method.

“Corn silage samples sieved through a 3.18-mm hole screen exactly as they would on 1.18 mm with a dry sample,” Cotanch reports. “Haylages take a 4.76-mm hole size to match up with the Ro-Tap system.

“Corn silages are right on the money,” he adds. “For some reason, haylages don't work as nicely. They're close, but they might be a couple of units off the Ro-Tap number.”

The researchers are testing the box on a wide range of forages from throughout the Northeast, planning to report their findings at the Cornell Nutrition Conference in October. Then they hope to start selling boxes in November.

Cotanch says the box will work on a wide range of ensiled crops as well as TMRs. While it's not intended as a replacement for the Penn State box, it may do a better job of helping to monitor rumen health. Recent research has shown that the amount of forage on the top two screens of that box isn't always an accurate indication of effective fiber.

“The Penn State box is very useful for characterizing particle distributions,” he says. “But as a nutritional tool, we've found a weakness in it. I think producers will eventually want to cue in on what their actual peNDF value is, whether they put it into a ration balancing program or not.”

For more information, contact Cotanch at 518-846-7121, ext. 123, or