Purdue's Low-Cost Hog Feed Lowers Manure Pollutants, Odors

Nitrogen and phosphorus in pig manure have been associated with ground water and surface water contamination, and the increasingly close proximity of neighborhoods to hog farms has brought a rise in public complaints about odors from confined-feeding hog facilities.

Purdue animal scientists Alan Sutton and Brian Richert worked with Purdue agricultural engineer Al Heber and others to develop the new diet.

"By reducing the crude protein of a standard hog diet and supplementing with synthetic amino acids and 5 percent cellulose, we were able to cut nitrogen excretion nearly in half," Sutton says. "The exact reduction of nitrogen in the manure was 48 percent."

By lowering crude protein to 10 percent and supplementing with synthetic amino acids alone, nitrogen in the manure was reduced by 33 percent, compared to excrement produced by hogs on a standard 13 percent crude protein diet. Ammonia emission -- another key odor-causer in manure -- also was reduced by 33 percent with this diet.

Adding 10 percent soybean hulls to such a diet resulted in a 40 percent ammonia reduction, and another odor-causing agent, hydrogen sulfide, was reduced by 26 percent. Total odors were diminished by 30 percent compared to that from pigs fed a standard diet.

In addition, the low-protein, soy-hull diet cost $3.86 less per ton than the standard diet.

Pigs had less backfat when fed the reduced-protein, soy-hull diet, but average daily weight gains dropped a little.

Richert and Sutton say a variety of management practices can reduce the chance of polluting the environment with excess nitrogen. They advise producers to carefully limit amounts of dietary protein by feeding high-quality, low-protein, amino-acid-supplemented diets to reduce nitrogen in manure.

The article about these dietary recommendations, "Nutritional Strategies for Reducing Manure DM, N, and P Concentrations," is written by Richert and Sutton.