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 Knowledge for the CommonWealth

Are You Feeding Excess Phosphorus?

Dairy Pipeline: May 1998

by Charles C. Stallings
Extension Dairy Scientist, Nutrition
Virginia Tech
540/231-4758 email:

Phosphorus along with nitrogen can cause a problem with ground water contamination. About 80% of dietary phosphorus is excreted, mainly in the feces. Intake and excretion are highly correlated, meaning that high phosphorus diets result in manure with high levels. In the past we have fed high producing cows in excess of 0.50% of the ration dry matter as phosphorus. One reason was that by-products feeds such as whole cottonseeds did not have the phosphorus efficiently utilized. Therefore, the logic was to increase the recommended amount when significant phosphorus was coming from feed sources. This logic has been shown to be faulty. The current recommended NRC level of phosphorus for high producing cows is 0.41% and is more desirable than the 0.50% that has been commonly used by practicing nutritionists. Research indicates no adverse effects on milk production or reproductive efficiency. This is a win-win situation. You can reduce supplement costs and at the same time help the environment. Have your nutritionist evaluate your level of phosphorus supplementation.

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