Scientists say they have taken a major step toward improving water quality in the Chesapeake Bay and throughout the country by feeding chickens a hybrid corn that sharply reduces the amount of phosphorus in their waste.
Researchers at the University of Delaware fed chickens the corn, along with an enzyme that helps the birds digest phosphorus more efficiently, and found the birds produced manure with 41 percent less phosphorus and 82 percent less water-soluble phosphorus. The mineral has been related to water pollution and outbreaks of Pfiesteria piscicida.
"That's really a dramatic reduction," said Victor Raboy, a research geneticist with the U.S. Department of Agriculture who helped develop the corn. "That's the kind of level of reduction people have been hoping for."
Rob Magnien, director of tidewater ecosystems assessment for Maryland's Department of Natural Resources, said the corn will have a "major initial benefit" in helping chicken farmers "meet nutrient management plans."
Farmers spread chicken manure on their fields as fertilizer, but the manure washes into rivers and streams, where it helps feed algal blooms, reducing the level of dissolved oxygen in the water and leading to fish kills and outbreaks of the toxic form of Pfiesteria.
The issue of controlling chicken waste is particularly important in Delaware and on the Eastern Shore of Maryland, where farmers produce nearly 6 million chickens a year, generating huge amounts of waste.
Maryland's Department of the Environment is preparing regulations expected to require the big poultry companies -- such as Tyson Foods Inc. and Perdue Farms, which own the chickens -- to take responsibility along with the farmers for disposing of some of that manure. In Delaware, the General Assembly approved legislation in July creating a permanent panel to draft and enforce rules for fertilizer use and storage.
Concerns about phosphorus in livestock waste are not limited to poultry farmers on the Delmarva Peninsula, says Raboy, whose laboratory is in Aberdeen, Idaho.
"It's not just the Chesapeake Bay, and it's not just chicken waste," he says. "It's Minnesota, Iowa, Missouri, all over the country. The problem I'm working on is phosphate in livestock. And that includes hogs and other livestock."
In Missouri, Premium Standard Farms, which produces 2 million pigs a year, agreed to pay $25 million to settle a suit accusing it of violating the state's Clean Water Act by spraying large amounts of manure on its fields as fertilizer.
In Kansas, the state health department has ruled that farms with more than 10,000 animals must line their waste pits with plastic to keep manure from seeping into ground water.
Raboy says he has been working on ways to reduce phosphorus for 10 years and with a team of researchers created the hybrid corn two years ago.
Chickens require phosphorus for muscle and bone development, but they can digest and use only about 25 percent of the phosphorus in corn. Raboy's hybrid can be digested more easily, and the birds can use 75 percent of the phosphorus.
In the Delaware study, done with the help of several agribusiness companies, more than 8,000 male chickens were fed six different diets, combining regular corn with and without the enzyme that helps digestion and the new hybrid with the same enzyme and decreasing amounts of other sources of phosphorus.
In addition to measuring phosphate in the manure, scientists measured how well the birds converted food to weight and whether the reduced phosphate caused skeletal problems.
"We were pleased to the point that we planted several hundred acres of this type of corn in Delaware," says Spangler Klopp, corporate veterinarian for Townsends, the Delaware-based poultry firm that supplied the birds.
The study proved the nutritional value of the corn, says Miloud Araba, director of poultry business development for Optimum Quality Grains, an Iowa feed company. "Now, let's do it on a commercial scale and see if it works."