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Modified Diet Reduces Chickens' Impact on Environment

Media Contact:
Jennifer Martin, CSREES Staff (202) 720-8188

October 30, 2007
By Stacy Kish, CSREES Staff

Chickens, like millions of Americans, are beginning a new diet. But instead of reducing their waists, this diet is intended to cut out excess waste, which creates a major pollution problem for waterways. Scientists at the University of Delaware devised a new poultry feed that limits the impact of animals on the environment.

William Saylor and colleagues at the University of Delaware evaluated a natural enzyme, called phytase, which helps animals digest more phosphorus. The addition of the enzyme to animal feed resulted in a 23 percent reduction in the phosphorus content of chicken manure.

Phosphorus is an integral component in any animal's diet, but scientists have known for some time that animals do not digest much of the phosphorus in most animal feed. Poultry are fed a diet of seeds and grains with the majority of the phosphorus in the form of phytic acid or phytate, a form that poultry can not digest. The undigested phosphorus is released in the animal's waste.

The development of phytase "has been at the nucleus of industry cooperation and regulations to deal with nutrients," stated William Rohrer Jr., administrator of the Delaware Nutrient Management Program. "It has significantly reduced the phosphorus going into our waterways."

Poultry waste is used for fertilizer. After years of applying litter to cropland, phosphorus accumulates in the soil, which can result in excess phosphorus leaching into local waterways. The addition of phytase to chicken feed results in less phosphorus in poultry litter.

The phytase-modified diet reduced phosphorus content of chicken litter by 25 to 40 percent in the last five years, dropping from 25 to 30 pounds of phosphorus per ton of chicken litter to 19 pounds of phosphorus per ton of litter. The modified diet has been accepted as part of the nutrient management practices adopted by poultry farmers under Delaware's Nutrient Management Law of 1999 and equates to a reduction in the environmental phosphorus load by some 2 to 3 million pounds per year.

A key part of the research involved observing animal productivity and health to be certain that both were maintained when birds were fed the modified diets. The birds were examined for bone health and growth beginning as chicks up to sale at market. This research defined the boundary of total phosphorus content necessary in animal feed to ensure animal health as well as reduce phosphorus content in animal litter.

The USDA's Cooperative State Research, Education, and Extension Service (CSREES) funded this research project through the Initiative for Future Agricultural and Food Systems program. CSREES advances knowledge for agriculture, the environment, human health and well-being, and communities by supporting research, education and extension programs in the Land-Grant University System and other partner organizations. For more information, visit www.csrees.usda.gov.