Enhanced Integrated Nutrient Management:

Top points from Larry Satter
Topic: Management of Dietary Phosphorus in Dairy Production Systems

1. Dairy producers feed phosphorus (P) to lactating cows about 20-25% in excess of National Research Council (NRC) recommended amounts.

2. Excess dietary P is excreted in the feces in a readily soluble form, and is potentially available as a contaminant of lakes and streams, promoting algae growth.

3. A lack of research showing the bare minimum of P required for lactation, and concerns that inadequate dietary P could impair reproductive performance, has contributed to excessive feeding of P.

4. Recent research has established that high producing dairy cows start showing P deficiency symptoms when dietary P approaches 0.30% of ration dry matter content.

5. The NRC recommendation that high producing dairy cows be fed diets containing 0.33 to 0.38% P is a good recommendation, and does provide some margin of safety.

6. There is no evidence in the literature of any benefit from feeding more than 0.38% dietary P to lactating cows. This includes observations on milk production, milk composition, animal health, and reproductive performance.

7. A cow fed 0.35, 0.40, or 0.48% dietary P, and producing 20,000 lbs of milk per lactation, will require 1.3, 1.6, or 2.0 acres of land, respectively, in the Upper Midwest to utilize the P excreted by the cow.

8. The dairy industry can significantly reduce the risk of P pollution of lakes and streams by removing excess P from dairy diets, and can save $12-15 per cow per year in reduced P supplementation costs.