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How to audit your TMR for consistency

Tamara Scully for Progressive Dairyman Published on 25 October 2018
cows eating at feedbunk

A cow feeding program is only as good as the as-fed ration. No matter how good things look on paper, the reality of the cow diet is determined, day in and day out, when feeders prepare and deliver the actual rations. If that as-fed ration deviates from the formulated one, the cows aren’t receiving the optimal nutrition you think you’re providing them.

“The goal is to get as close to the nutritionist’s paper as possible,” Bill Stone, DVM, of Diamond V, said to attendees at last fall’s Cornell Cooperative Extension and PRO-DAIRY Feeder School. “You need systems in place with any feeding program, just like with milking programs.”

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An audit of your total mixed ration (TMR) examines feed storage and preparation, ingredient mixing and delivery of the ration. During any or all of the steps involved in getting feed from the bunk to the cow, the composition of the as-fed ration can be compromised. The resulting inconsistency in the diet is undesirable, with the nutritional content of each bite variable. Ration variability from bite to bite isn’t conducive to a healthy rumen and can impact milk production. Ration differences from cow to cow, due to inconsistency in mixing, are another concern.

A complete TMR audit includes a review of feed center organization, defacing protocol, mixing wagon performance and an examination of refusals. Other elements, such as coordinating feeding with the milking or barn cleaning schedules, that impact feeder efficiency are also examined.

Bunk silo defacing

A well-monitored feeding system begins with bunk management. Packing the bunk silo to decrease spoilage is the first step, but defacing the bunk properly to maintain quality and consistency of the fed ration is equally imperative. The edges of the plastic covering the bunk should be properly weighed down and only removed – following safety procedures – to allow daily defacing, minimizing feed exposure to wind, air and precipitation. An organized feed center provides protection from wind and rain, makes the feeder’s job more efficient and ensures that old ingredients are used before new feed.

Because the bunk’s face is subject to vertical variations in feed quality, defacing the bunk first and then co-mixing the defaced portion is the proper way to prepare the feed. This ensures that moisture and nutrient levels remain as consistent as possible throughout the defaced silage. Once this defaced silage is mixed together for consistency, it is then ready to be added to the mixer wagon.

A minimum of 6 inches in the winter or 12 inches in the summer is typically defaced per day, with less densely packed silage requiring added defacing. There should be little, if any, loose silage left on the ground after the day’s feeding.

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Proper ingredient mixing

“Everything falling together at the same time” is the key, Stone said, and depends primarily on the mix time and the equipment’s functioning. If the mix time is correct, and the TMR mixer wagon has been properly maintained, the as-fed ration will have a much better chance of matching the nutritionist’s paper ration.

The mixer wagon is used heavily and needs regular maintenance. Buildup of sticky feed around the augers, loose blades or parts, oil leaks, tire pressure and dirty radiator screens should be addressed daily by the feeder. Wear on augers, knife belts and auger kicker plates should be checked at least every quarter. Other routine equipment maintenance, such as checking oil levels or doing oil changes, should occur on a regular scheduled basis.

The auger rotation per minute (RPM) can be one common reason why mixing isn’t consistent, Stone noted. Worn auger kicker plates won’t mix uniformly. Dull blades can’t process hay, and inconsistently mixed hay will promote sorting by the cows. Mixing on an uneven surface causes heavier ingredients – like concentrates – to settle to the bottom. Overfilling the mixer prevents proper mixing, although underutilization of the mixer could be an issue on smaller dairies.

After the last ingredient is added, the mix time changes with load size, mixer specifications and ingredient moisture levels. Whether using a vertical or horizontal auger, or a payloader, proper mixing techniques will have a significant effect on the as-fed ration.

Assessing the ration

“We do the shaker box to evaluate how well we do mixing and to make sure we have appropriate length without too many fines,” Betsy Hicks, Cornell cooperative extension dairy specialist, said. “You would use the information to adjust mixing time or add chopped hay or straw.”

Using a Penn State shaker box, mixed TMR is sorted by particle length as it passes through a series of sieves. For high-producing dairy herds, the upper sieve should collect no more than 8 percent of the ration material, while 30 to 50 percent should settle into the middle sieve, with 10 to 20 percent in the 4-millimeter sieve, with no more than 40 percent left in the bottom, or smallest diameter sieve.

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“If there is too much in the top pan, we may have to mix longer to break long pieces down. We also don't want too much length on the top box, because we can start to limit intake by being too bulky of a diet. If there’s too little, we can shorten mixing time – to a point – or add a pound or two of chopped hay or straw to make sure we have adequate length,” Hicks explained. “Some nutritionists will use shaker boxes on individual ingredients, but my personal bias is that I want to know what the end product is that the cow sees – the TMR.”

Refusals, which should be cleared just prior to the next feeding time to limit any time without feed present, should also be examined with the shaker box to evaluate if cows are sorting. If so, there will be very little material in the bottom box, and quite a bit in the top and middle boxes. The closer all boxes are to having the same amount of material settling into them, the less the cows are sorting, which is the goal, Hicks said.

Feed is a primary cost of production for dairy farmers, and cow performance is directly related to the ration fed. Performing an audit to verify that your fed ration is as close as it can be to the one on paper is cost-effective and can help find inefficiencies in your feeding program.  end mark

Tamara Scully, a freelance writer based in northwestern New Jersey, specializes in agricultural and food system topics.

PHOTO: Performing a TMR audit to verify that your fed ration is as close as it can be to the one on paper is cost-effective and can help find inefficiencies in your feeding program. Photo by Mike Dixon.

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