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The TMR Mineral Mismatch

Virginia A Ishler, Penn State Extension

Frequent forage testing and regular updates to diets help achieve precision feeding.  Ration formulation has come a long way with advanced computer models and balancing requirements based on many details related to the animal and the feeds. To reap the benefits of the nutritional research conducted over the past decades good feeding management practices are needed. It still boils down to how well the ration is being implemented on farm, which in some cases may vary greatly from the formulated diet.

Production Perspective

Starting in 2016 twenty-four herds began an on-farm project to evaluate practices related to cropping, feeding and financial management. During the sampling period, which included the analysis of the lactating cow total mixed ration (TMR), information was collected on the feeding weights and refusals, pounds of milk shipped, and the nutritionist’s ration. One of the major goals of the project is to evaluate precision feeding – how closely does the TMR analyses match the formulated ration for nutrient specifications, dry matter intakes and milk production. Protein and carbohydrates are critical nutrients in precision feeding however, some interesting observations on calcium and phosphorus agreement have materialized.

Nineteen of the twenty-four farms have complete data for 2016 and their average production was 78 pounds. There was very good agreement on the dry matter percent with the actual TMRs trending wetter (45.5% dry matter) than the formulated (46.2% dry matter) and the difference was less than one percent on average. Basing dry matter intakes on the batch weights fed (including refusals) and the dry matter percent from the TMR, there was generally good agreement with the trend being on average 0.70 pounds lower actual intakes compared to the formulated ration. Two herds were big outliers, one came back consuming 10 pounds less dry matter than expected and the other herd 10 pounds more than formulated. 

The discrepancy and range in calcium levels tested and formulated were huge. The range in calcium percent was 0.63% - 1.63% for actual and 0.59% - 1.00% for formulated however, the lows and highs did not match on the respective farms. When herds were divided based on milk production (<69 lbs., 70-79 lbs., 80-89 lbs., and >90 lbs.) the low production group had the greatest mismatch on calcium percent in the diet. For the herds averaging over 70 pounds, the agreement between actual and formulated was very similar. When calcium intake was evaluated, there was no pattern based on milk production but it was fairly consistent that cows were consuming more calcium (0.48 pounds) compared to the formulated ration (0.44 pounds). The range for calcium intake was very broad (0.33 lbs. – 0.65 lbs.).

Phosphorus is generally the mineral of most interest due to its environmental concerns. Overall, there was good agreement with the actual trending higher on average compared to the formulated (0.42% versus 0.38% on a dry matter basis, respectively). The lower producing herds tended to have the lower percent phosphorus and the higher producing herds the higher percent. The positive aspect on the phosphorus is the excellent agreement on the pounds fed (actual and formulated). Only four herds had phosphorus exceeding the cow’s nutrient requirement (average 0.28 lbs.) with one farm deliberately formulating for the higher level.   

The herds participating in the Extension Dairy Team’s project would be considered very progressive and well managed. There is a tendency to focus on the key nutrients that influence milk production and performance. Minerals should not be overlooked in their agreement between the actual ration fed and the paper diet. A mismatch on calcium and phosphorus can give insights on where bottlenecks may be in nutrition or management. The other major and trace minerals can give clues to problems in mixing or ingredient nutrient content.

Action plan for implementing precision feeding.


Validate mixing procedures and ingredient specifications by analyzing the total mixed ration at least two times per year.


  • Step 1: Determine key times during the year when TMR sampling would be appropriate.

  • Step 2: Record batch weights, refusals and the number of cows fed when the TMR is sampled.

  • Step 3: Calculate the actual dry matter intake based on the batch weights and the dry matter percent of the TMR.

  • Step 4: Compare the TMR analysis with the formulated ration. Discuss any discrepancies with the nutritionist and feeder.

  • Step 5: Record milk production and intakes. Make notes of any events that may have affected results.

Economic perspective

Monitoring must include an economic component to determine if a management strategy is working or not. For the lactating cows income over feed costs is a good way to check that feed costs are in line for the level of milk production. Starting with July's milk price, income over feed costs was calculated using average intake and production for the last six years from the Penn State dairy herd. The ration contained 63% forage consisting of corn silage, haylage and hay. The concentrate portion included corn grain, candy meal, sugar, canola meal, roasted soybeans, Optigen (Alltech product) and a mineral vitamin mix. All market prices were used.

Also included are the feed costs for dry cows, springing heifers, pregnant heifers and growing heifers. The rations reflect what has been fed to these animal groups at the Penn State dairy herd. All market prices were used.

Income over feed cost using standardized rations and production data from the Penn State dairy herd.



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