Sep. 12, 1997 Managing the 19.5 million tons of chicken and turkey manure produced each year by the U.S. poultry industry is no simple task, but a Penn State poultry nutritionist is looking at ways to more carefully balance chicken diets and reduce waste.
"Nutrient management is an important aspect of chicken production and benefits both cost and animal health," says Dr. Paul H. Patterson, assistant professor of poultry science. "Management of poultry feed can also control the amounts of nitrogen and phosphorus that passes through the birds and becomes a waste disposal problem."
The options for manure use are many, but the more practical ones are fuel, feed and fertilizer. Chicken manure can be burned, producing one third the fuel value of coal, or converted to methane in biomass converts. Chicken manure can also be used to feed ruminant animals, such as cattle, that can extract unused nutrients. However, the most common use for chicken manure today is as a fertilizer for agricultural fields.
Excess nutrients in fertilizer are a source of non point source pollution targeted by environmental initiatives like the Chesapeake Bay Pollution Program. The two components of chicken manure that cause the most concern for runoff are nitrogen and phosphorus, but both elements are necessary for good bird health, egg laying and weight gain.
"U.S. lawmakers are looking to the Netherlands' Policy on Manure and Ammonia as a model because it aims for nutrient equilibrium," Patterson told attendees today (Sept. 9) at the fall meeting of the American Chemical Society in Las Vegas, Nev. "The Dutch approach is to match the amount of nitrogen and phosphorus in fertilizer applications with the crop requirements.
"Today, some producers manage their birds to minimize manure and nutrient production, in essence, designing chicken manure to reduce the load on the environment."
Farmers can control the nitrogen content of manure by using better feed formulation, lower protein diets, and feed additives. In many cases, these approaches save money as well as control the nitrogen output of the birds.
Modern breeds of laying and meat birds are more efficient than older varieties. In a study funded by the Pennsylvania Poultry Foundation, Patterson has reevaluated the nutrient balance of modern birds to better optimize nutrition and cost.
"By looking at available rather than total protein, farmers can lower the protein content of feeds and reduce the amounts of nitrogen in manure," says Patterson. "Synthetic amino acids are also cost effective and reduce nitrogen waste."
The practice of phase feeding -- tailoring feed to the life cycle of the bird -- also reduces nitrogen waste. Feed additives that allow birds to better use available nutrients can also help.
Controlling excess phosphorus centers around supplying phosphorus in a form the birds can use. Feeds such as corn and sorghum contain only 19 to 22 percent bioavailable phosphorus with the rest in a chemical form difficult for the birds to digest. The phosphorus in meat or fish meal is 81 to 100 percent bioavailable so birds require less phosphorus in their feed thereby reducing the amount of phosphorus in the manure.
"Some forms of vitamin D can improve phosphorus retention by 20 percent," says Patterson. "Enzymes added to the diet can also improve phosphorus uptake."
Reducing the nitrogen and phosphorus in feeds, in many cases, decreases the cost of the feed. Lowering the nitrogen and phosphorus levels in the manure can also reduce disposal costs for the enormous amounts of chicken manure produced by the poultry industry each year.
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