Distiller's grains offer new opportunities for dairy producers. However, there is concern over the possibility of increasing the amount of phosphorus that cows excrete in manure.
A study by Cornell University found that incorporating moderate amounts of corn distillers dried grains with solubles (DDGS) at 10 percent of diet dry matter did not significantly increase phosphorus excretion in lactating cows. When DDGS increased to 20 percent of the diet dry matter, manure phosphorus increased about 20 percent. Dry cows and heifers are more sensitive due to their lower phosphorus requirements. When DDGS was fed to dry cows and heifers at 10 to 13 percent of diet dry matter, the amount of phosphorus excreted in the manure increased by 20 to 25 percent, according to an article in the December 2009 issue of the Journal of Dairy Science. It is important to remember that these results apply to the feeds and assumptions used in this trial. Work with your clients to review the ration phosphorus levels as they evaluate the feeding level of DDGS in their herds. If ration phosphorus levels increase above requirements when DDGS is added, the quantity of phosphorus excreted in the manure is expected to increase.