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Virginia Cooperative Extension - Knowledge for the CommonWealth

Virginia Tech ration mineral analysis for the lactating herd recently checked

Dairy Pipeline: November 2001

Charles C. Stallings
Extension Dairy Scientist, Nutrition

We are currently doing several research projects at the Virginia Tech Dairy Center involving feeding of both macro and micro minerals. As a result we have been evaluating our rates of supplementation. A recent lab test indicates total mixed ration calcium is 1% of dry matter, phosphorus .40%, magnesium .28%, potassium 1.87%, sodium .41%, iron 269 PPM, zinc 67 PPM, and manganese 79 PPM. We have had a problem with analyzing for copper and no results are available for it as well as iodine and selenium. These concentrations meet or exceed the 2001 NRC guidelines. Our mineral mix contains molasses, zinc sulfate, limestone, potassium & magnesium sulfate, manganese sulfate, mono/di calcium, phosphate, salt, potassium chloride, trace mineral premix, EDDI (iodine), magnesium oxide, vitamins A, D, & E, and selenium premix. How do these numbers look relative to excess nutrients in the ration? Calcium is not typically a concern and the 1% concentration is typical when fat or high fat feeds are in the ration. We feed whole cottonseeds to our herd. Phosphorus is the mineral of most conern in terms of the environment and indications are we have been over supplementing in the past. The .4% concentration is in line with the current thinking and still may be more than is needed. We have phosphate in our mineral mix but some herds may not need any especially if using a lot of byproduct feeds high in phosphorus. Research from Virginia Tech indicates the phosphorus in these feeds is available to the animal. The other mineral concentrations are not a concern but we do know that some of the trace minerals can be a problem at high levels due to various interactions. The levels we are feeding are within two times the requirements except for iron. Iron typically is high because of the amount in forages but may not be in a form to be digested. Two times the requirement for the trace elements is not generally excessive except for selenium. Since many of the trace minerals interact and compete for absorption excess amounts in the diet should be avoided.

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