Mixing the perfect dairy ration requires precision. Good-quality ingredients, measured accurately and mixed properly, will produce the best bunk chow for your cows. But controlling those three factors is easier said than done, according to a study in Winona County, MN.

Focusing on forage particle length and its importance in blending total mixed rations (TMRs), county extension educator Neil Broadwater set out to discover just how well dairy farmers were doing. And he wasn't the only one who was curious. Plenty of producers in the southeastern Minnesota county were anxious to get some fiber feedback.

“I sent out a letter explaining my study to every dairy producer in the county with over 100 cows, knowing they probably had TMR mixers,” says Broadwater. “I met my goal of 30 cooperators in no time. I even had three other farmers who called, pleading to be included.”

What did he find out? On average, the particle lengths in rations from TMR mixers were within the guidelines used by most dairy nutritionists.

“But averages don't mean much when you're looking for consistency from ration to ration,” says Broadwater. “The study results showed us there was a wide range in particle length from sample to sample and from farm to farm. It's that kind of variability that causes milk production problems.”

Insufficient functional fiber can cause cows to go off feed, produce less milk and lower fat tests, and can lead to laminitis and even liver abscesses, he adds.

“There was a tendency to overmix rations,” according to Broadwater. “As they fill the mixer with the various forages and grains, producers don't realize how quickly the mixing can reduce particle length.”

He says the key to getting lengths right, batch after batch, is first knowing what's happening at the bunk.

“You've got to know what the cow is consuming, and just as importantly, what she isn't consuming. Is there sorting going on, with long particles left in the bunk, or are they licked clean?”

With that information, you can work backward to determine where and how you need to make management changes, he says.

“Maybe you need to adjust your mixing time, or your mixing procedure, or maybe you need to go back a step further and adjust your harvesting length in the field.”

To help farmers get a better handle on how ration mixing impacts particle length, Broadwater trained intern Aimee Finley to use a Penn State forage particle separator. It has three screened boxes for segregating ration ingredients of various lengths.

Traveling to each of the 33 participating farms three times over the course of the summer, Finley used the separator both before and after rations were mixed.

The amount of ingredients that ended up in the top box of the separator (¾" and longer particles) ranged from 2% to 48% of the total ration. The University of Minnesota's recommended range is 7-10%. In the middle box (0.31-0.74" particles), the amount ranged from 33% to 56%, with the recommended range being 45-55%. In the bottom box (0.30" and smaller particles), the amount ranged from 27% to 62%, while the recommended range is 40-50%.

Finley also analyzed samples of haylage and corn silage with the separator. Those results can be viewed on the Internet at www3.extension.umn.edu/county/Winona/images/dyfiberstudysummary.pdf

The lesson to learn from these numbers is that, if you don't pay close attention to your mixing, it's likely that particle lengths will vary greatly from ration to ration.

“You can't have wide ranges like this and expect that cows will do well. Consistency is the key,” says Broadwater.

To achieve ration consistency, he makes the following recommendations:

  • Develop a mixing procedure and follow it every time. Even a change in who does the mixing can make a big difference in the ration.

  • Watch ingredient weights carefully; make sure they're right on, every time.

  • Watch mixing time closely. You may have to change the ingredient sequence to avoid overmixing forages.

  • Do regular analyses of particle lengths.

“It certainly wouldn't be out of line to do it every month,” says Broadwater. “Yes, it's another chore, but it's a very important management practice.

“Many farmers rely on their nutritionist to do it, and that's OK,” he notes. “But farmers might want to consider buying their own separator. They're a very worthwhile investment.”

Did the farmers change some of their practices because of last year's study? That's what Broadwater hopes to find out from a follow-up study he completed this summer, although he's still collecting the numbers.

“I know farmers were very interested in what we found last year, and several of them started to make changes in their mixing procedures, a few in their forage harvesting,” he says. “What we want to know this year is whether they're still monitoring particle length regularly — that's the key.

“It all comes down to knowing what's in the bunk and whether the cow is eating it. If you have a handle on that, everything else will fall into place.”