Environmental improvement not just chicken feed

If you’ve been dieting lately, you have some company that might surprise you—chickens.

Millions of them in Delaware, one of the nation’s top poultry producers, have been on a diet to reduce their impact on the environment and improve the health of the state’s waterways. And, researchers say, it appears to be working.

Extensive studies led by William Saylor, professor of animal and food sciences, have confirmed that Delaware chickens now digest more of the phosphorus, an essential nutrient, in their feed, thanks to the addition of a natural enzyme called phytase. As a result, the chicken’s manure contains about 23 percent less phosphorus than it did before the enzyme was used.

So now, when poultry litter is used to fertilize a farm field, a lot less phosphorus is available to potentially leach from the soil or be carried off in storm water to a river or bay.

That’s good news for Delaware’s Inland Bays and other waterways, where overloads of nutrients, particularly phosphorus and nitrogen, have contributed to such serious water-quality problems as massive blooms of algae and fish kills.

To put it in perspective, Delaware farmers last year produced about 269 million broiler chickens—1.8 billion pounds of poultry—valued at more than $739 million, according to the Delmarva Poultry Industry. Those chickens produced more than 280,000 tons of waste.

According to recent analyses by David Hansen, assistant professor of plant and soil science, who studies soil and environmental quality, a ton of Delaware poultry litter currently contains about 19 pounds of phosphorus, compared with 25-30 pounds just five years ago. The 30-40 percent reduction is credited to phytase-modified diets and other nutrient management practices adopted by poultry farmers under Delaware’s Nutrient Management Law of 1999. The reduction means that the phosphorus load to the environment has been reduced by some 2 million to 3 million pounds per year.

“Phosphorus is essential to all life,” Saylor says. “Livestock, particularly poultry and swine, are fed a diet of seeds and grains. However, two-thirds of the phosphorus in this food is phytic acid or phytate, which is a form of phosphorus that poultry and pigs can’t digest, so it goes right through them.

“Phytase is an enzyme that is added to poultry feed at the mill that helps broilers and other poultry utilize more indigestible phosphorus.”

Over the past several years, Saylor and colleague J. Thomas Sims, the Thomas A. Baker Professor of Plant and Soil Sciences and associate dean of the College of Agriculture and Natural Resources, have led a team of experts in analyzing the nutritional requirements of poultry and swine. The researchers have examined the effects of phytase-modified diets on the livestock and on the environment as part of a “feed-to-field” approach to nutrient management. The research was funded by an $821,000 grant from the U.S. Department of Agriculture.

The scientific team included poultry nutritionists Roselina Angel from the University of Maryland and Todd Applegate from Purdue University; and Wendy Powers, a swine nutritionist formerly at Iowa State University and now at Michigan State University.

At UD, Saylor and his students formulated various phytase-modified diets for a series of studies involving thousands of broiler chickens. The birds were examined for bone health and growth, as well as the phosphorus content of their manure, beginning as chicks and continuing until they were market-size birds.

The painstaking research defined the boundary at which the total phosphorus levels in a broiler chicken’s corn-soybean-meal diet can be reduced without harming the bird’s health, as well as the percentage of phytase that can be added to the feed to allow the birds to digest more phosphorus, leaving less to literally “go to waste.”

The data have been shared with a nutrient management partnership involving the poultry industry, environmental regulators and the academic community.

“It certainly factors into our decision-making process,” Ted Miller, director of nutrition and research at Mountaire Farms Inc., in Selbyville, Del., says of the research.

Miller serves on an advisory committee in the College of Agriculture and Natural Resources and meets regularly with UD and Maryland scientists as an industry cooperator.

“Phytase has been at the nucleus of industry cooperation and regulations to deal with nutrients,” William Rohrer Jr., administrator of the Delaware Nutrient Management Program, says. “It has significantly reduced the phosphorus going into our waterways.”

William Vanderwende, chairperson of the state’s Nutrient Management Commission, says he has been contacted by several states that want to model their nutrient management program after Delaware’s.

John Schneider, manager of the Watershed Assessment Section at the Delaware Department of Natural Resources and Environmental Control, calls phytase “a positive piece of the water-quality puzzle” that is having an impact.

“We are seeing less phosphorus in water samples from all over the state,” Schneider says. “Clearly, we’re doing a lot of things right.”

—Tracey Bryant