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Audit team: Worn mixer knives frustrate feeder and milk yields

Brian Perkins Published on 09 February 2012
over filled feed mixer

One of the main goals of a dairy business is to maintain a consistent environment for its cows. Daily routines for the cows should occur at the same time every day, with their physical environment varying as little as possible.

Freestalls, milking barns and corrals should be maintained so cows don’t experience any drastic daily differences.



One aspect of the cow’s life that is often taken for granted is the presentation of the TMR.

After all, the nutritionist balances the ration on a computer using the latest and greatest ration software, the diet is entered into the most current version of feed management software, and the TMR is mixed in a high-tech mixer worth tens of thousands of dollars. After all of that, the TMR has to be correct, right?

One of the things our Diamond V consultants have found after running more than 400 TMR audits is that TMRs are much more inconsistent than you might think.

One of the goals that we often lose sight of is providing an extremely consistent rumen environment for the microbes, and, in order to do this, we must create a TMR that doesn’t vary from one end of the feedbunk to the other and from the top of the TMR to the bottom.

TMR audits involve taking 10 sequential samples from each of the multiple loads of TMR, shaking them through a Penn State Shaker Box and analyzing the results statistically and graphically.


During an audit, the auditors also observe the behavior of the feeders in how they remove silage from piles or bags, how they handle grain ingredients, how they work with equipment, if there are shortcuts in the mixing process and whether there are changes to their work routine that would streamline the mixing process.

We also ask for input from the feeders regarding how to make the process more efficient. The feeders often have wonderful ideas, but sometimes they don’t have an opportunity to express them.

The audit may also involve using an infrared imaging camera to evaluate storage and handling of silages and to see where heating is occurring. The TMR audit also includes checking the maintenance and condition of the mixer, observing whether bunks are being read properly or whether dropped feed is being adjusted for push-out amounts.

It also includes an analysis of feed software reports, with particular attention to daily feeding times and bunk calls, coordination of feeding times with milking times, and any other issue deemed important by the manager and/or nutritionist.

At the end of the audit, the manager is given a report and slide presentation with key observations and recommendations that can be used in conjunction with input from the feeders to improve feeding routines and to improve consistency of mixing and delivery of the TMR that will ultimately create a healthier rumen environment for the cows.

One such TMR audit in which I was involved happened at the request of a nutritionist who was frustrated with butterfat running roughly two points lower than typical for that dairy during that time of year. We arrived at the dairy well before dawn to watch the entire feeding process from start to finish.


The feeder was very careful with his handling of both forages and grains, and he seemed to be extremely concerned about hitting target weights in the mixer within tolerances.

One issue that surfaced early was that he was running the mixer for roughly 10 minutes after he added the hay and before he added any other ingredients.

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When questioned about this lengthy mix time, he indicated that he had to increase mix time in order to get the hay processed adequately. We also noted that the mixer was filled well beyond capacity. ( See Photo 1 at top )

We watched him unload the first TMR and were surprised to see him driving forward and backward along the feedbunk to drop feed. This turned out to be his attempt at evening out a poorly-mixed TMR.

Photo 2 depicts what the manger looked like that morning. There were clumps of low-quality hay in many locations along the manger, and cows were sorting around them as they ate the TMR.

Statistical analysis of the sequential shaker box samples showed exactly what one would expect – substantial variation in the amounts on the top, middle and bottom screens of the shaker box.

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We also used the infrared imaging camera to analyze forage storage and handling. Corn silage in the pit was acceptable, but silage piled on the feed pad overnight was very hot, as shown in Photo 3 .

After the feeder was done with his morning routine, we were able to look inside the mixer to observe the condition of the augers and knives.

Photo 4 shows what we saw: Knives so worn it was almost impossible for them to process hay, straw or any long-stem forage.

When we finished, we made several recommendations to the feed manager. The first was to immediately replace the worn mixer knives with new ones.

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Second, reduce the batch size so the mixer was no longer filled over its top line. Third, add a portion of the coarser hay (about 5 lbs) to the grain premix, so that it would be preprocessed before adding it to the TMR.

Finally, we recommended bringing the silage from the pit to the feed pad early in the morning rather than the evening before to avoid heating and potential growth of unwanted organisms.

The manager implemented these suggestions almost immediately, which was very gratifying since he was anxious to regain the lost butterfat. Within two weeks butterfat had climbed two points, and milk was up 1 to 2 pounds.

The feeder was also pleased, because after the knives were replaced his mixing time was decreased by about eight minutes per batch. He no longer had to drive forward and back while dropping TMR in the mangers.

The TMR audit was able to point out several areas for improvement that were easy to implement and helped create a better rumen environment for the cows and more profit for the dairy. PD

Perkins has a Ph.D. in nutrition and reproductive physiology from Cornell University and is employed by Diamond V as a technical service specialist for the western United States.

PHOTO 1: Feed mixer filled well beyond capacity.

PHOTO 2: Clumps of low-quality hay in many locations along the manger.

PHOTO 3: Silage piled on the feed pad overnight was very hot.

PHOTO 4: Knives so worn it was almost impossible for them to process hay, straw or any long-stem forage. Photos courtesy of Brian Perkins.

Brian Perkins
  • Brian Perkins

  • Technical Service Specialist
  • Diamond V Research and Technical Services
  • Email Brian Perkins