A new addition to the Penn State forage particle separator can help dairy producers get an even better analysis of their TMRs, says Jud Heinrichs.

“With the majority of TMRs we were sampling with the original separator, easily 40-60% of it was falling through our second screen,” says Heinrichs, a Penn State extension dairy nutritionist and a member of the research team that developed the separator. “We weren't getting a good analysis on a major fraction of that TMR.”

Introduced in 1996, the Penn State forage particle separator is a tool for measuring or evaluating the overall size of the feed particles being fed. The original model features three boxes and two screens or sieves. The top box has holes that are 0.75” in diameter, while the middle box has holes that are 0.3” in diameter. The bottom box is solid.

The new separator has a fourth box and a third screen with a pore size of 0.05” or 1.18 millimeters (mm), which is the standard mesh for a grain screen.

There are several reasons why Heinrichs and his colleagues chose 1.18 mm as the pore size on the new screen.

“That figure is used in an equation developed by Dave Mertens at the U.S. Dairy Forage Research Center to help determine effective fiber,” he explains. “It's also been determined by a couple of different references as being the average particle size of a piece of feedstuff leaving the rumen of a cow.”

“The addition of the third screen gives us another fraction to evaluate in the TMR,” notes Mike Hutjens, University of Illinois extension dairy nutritionist, who has just started using the new box and screen.

Ideally, no more than 8% of the TMR material should be retained on the upper sieve after the recommended shaking procedure. New Penn State guidelines for TMRs for high-producing dairy cows are 2-8% of the particles in the upper sieve, 30-50% in the middle and lower sieves and no more than 20% in the bottom pan.

When minimum fiber levels aren't met in a cow's diet, total dry matter digestibility can be reduced, milkfat percentage can taper off and cows can develop rumen acidosis and other health problems.

“It's been demonstrated that reduced forage particle size decreases the time a cow spends chewing and causes a trend toward decreased rumen pH,” says Heinrichs. “When cows spend less time chewing, there's a decrease in the production of saliva needed to buffer the rumen.”

Heinrichs hopes the new screen and box will gain acceptance among dairy producers and nutritionists worldwide, just as the original separator has.

“I've talked about dairy nutrition and the separator in several countries this year and it's used in all of them.”

The new box fits most Penn State forage particle separators and can be purchased separately, he says.

“It won't fit the first-generation separators, which have pegs, but it should fit all separators sold in the last three years.”

The particle separator and new box are commercially available only through Nasco in Ft. Atkinson, WI. The new box, which retails for $77.50, isn't included in Nasco's latest catalog. Ask for item No. C24078N. The telephone number is 800-558-9595.