Poultry scientist Paul Patterson shares strategies that reduce phosphorus in poultry manure.

What farmers feed their animals affects the concentration of nutrients in the manure. Extension programs run by animal scientist Ken Kephart and poultry scientist Paul Patterson focus on reducing the amount of phosphorus and nitrogen in animal diets. "Ordinarily, pigs can't digest most of the phosphorus in corn or soybean meal because it's tied up in a compound called phytic acid," Kephart says. "So producers compensate by adding inorganic phosphorus to the feed. Rather than jeopardize the performance of the animals, they often added excess phosphorus as a safety margin. But now that swine operations are larger and volumes of animals greater, it makes economic sense to make formulations more precise. It also makes sense environmentally. If producers add less inorganic phosphorus to the feed, less phosphorus goes into the manure. This helps bring the ratio of phosphorus to nitrogen in manure more in line with what crops require."

Producers also are beginning to add an enzyme called phytase to diets, which allows animals to glean more phosphorus from feeds. "Phytase cleaves open the phytic acid -- it's like cracking a peanut," explains Joe Garber, nutrition and analytical services coordinator for Wenger's Feed Mill, Inc. "This allows the animal to obtain more phosphorus." Wenger's Feed Mill, which produces feeds for animals in south central Pennsylvania and parts of Maryland and Delaware, has added phytase to their feed since May 1995. Phytase had been used in Europe since 1990, but it wasn't approved for sale in the U.S. until the spring of 1995, Garber explains. "We immediately began using it in feeds for layer birds, decreasing our use of inorganic phosphorus by 25 to 30 percent, and still got equivalent performance. It only took three weeks for our inorganic phosphorus suppliers to call, wondering what was happening."

Because enzymes are proteins, they're heat-sensitive. Feeds for layer birds aren't heat-processed, so Wenger's was able to add the enzyme to the mash. But the pellet feeds used for broilers, turkeys, and swine are another story. "To make pellets, we grind the feed, heat it with steam to agglutinize the starches, then run it through a pellet mill -- a kind of glorified pasta maker," Garber says. "The phytase would volatilize during the process. But in the last 18 months, a new technology has allowed us to spray the enzyme on the feed after it's cooled down, so we can expand its use to other animals. We get monthly phone calls from producers who are looking for help to reduce the amount of phosphorus in their farm's manure. Feed companies need to give producers a manure they can work with. At the same time, we have to do it economically and not harm the performance of the birds or swine. That's what phytase has allowed us to do."

Except for the initial equipment costs, Wenger's savings from buying less inorganic phosphorus compensate for the price of the phytase. "The product pays for itself," Garber says. "That's the tangible benefit. But there's also the intangible benefit of being environmentally friendly and proactive, which is valuable beyond dollars and cents."

Sam Young (front left), professional engineer with Larsen Design Group in Bloomsburg, and senior extension associate Robert Mikesell (front right) conduct an on-farm odor and environmental assistance audit, while pork producer Matt McClellan (back left) of Granville Summit and Ken Kephart (back right) discuss nutrient management strategies.

To share strategies such as phytase with swine producers, Ken Kephart and county agents conduct environmental audits of swine facilities. The audits cover pollution prevention strategies, odor, disposal of dead animals, manure storage and treatment, and community relations. "We walk through the operation and talk with the producer about all the things he or she is doing that affect the environment, then make suggestions for improvement," Kephart says. "There's no more effective way to get a producer to change his actions than getting on the farm and talking face-to-face." So far, specialists have visited more than 120 swine operations, which included more than 275,000 hogs. "Most of the operations are already environmentally sound," Kephart says, "but these audits help producers make further improvements."

Poultry producers can use similar strategies to minimize the amount of phosphorus excreted in poultry manure. "Selecting ingredients with highly available phosphorus, such as meat and fish meal, instead of cereals can make a major impact," says Paul Patterson. "Another strategy is to decrease calcium in the diet, because too much calcium reduces phosphorus retention. Producers can add more vitamin D to feed, add phytase, and not add extra phosphorus. We can also avoid stressing the birds, because they excrete more phosphorus when they're under stress."

Patterson also has applied a modified lighting program that reduces the amount of calcium hens draw from their bones when making eggshells -- a process that releases phosphorus. "When hens draw calcium from their bones, rather than from the food in their gut, they release phosphorus into their urine," he says. "The modified lighting program gives them 15 minutes of light every hour for 19 hours each day, which encourages small meal feeding throughout the day. That way, the hen doesn't eat large meals, deposit calcium in her bones, then draw it out later when making eggshells." Some phosphorus still will be excreted in the manure, but producers also can add compounds to the manure, such as alum, to prevent it from washing off into surface waters, says Patterson.