Satter surveyed consultants, feed industry reps and state extension specialists across the nation last year, and found that on average, diets for milking cows contained about .48 percent phosphorus.
Many producers feed high phosphorus levels in hopes of improving reproductive performance.
That's a barnyard myth, at least for dairy cows. At very low phosphorus levels, .15 percent to .2 percent, reproduction can suffer. Beef cows might encounter these levels grazing corn stalks or winter pasture, for example. Reducing the amount of supplemental phosphorus to NRC-recommended levels will save money and also reduce the phosphorus in manure by 25 percent to 30 percent. Current regulations in Wisconsin are based on nitrogen levels, and apply to herds of 700 cows or more.