Here’s a thought worth chewing on: By better managing what goes in an animal’s mouth, scientists say they can reduce—sometimes dramatically—the amount of nutrients coming out the other end.

The potential nutrient reductions are not small potatoes, either.

Chickens, cows, cattle, hogs and turkeys in the Bay watershed churn out about 44 million tons of manure each year. Altogether, they are responsible for about a fifth of the nitrogen and phosphorus entering the Bay.

Researchers, farm advisers and water quality managers increasingly believe the best way to deal with those nutrients is to keep them from coming out of the animal to begin with.

When the Chesapeake Bay Commission last year reported on the six most cost-effective strategies for cleaning up all nutrient sources to the Bay, it ranked diet and feed adjustments second behind wastewater treatment plant upgrades.

“By far, the most cost-effective way to minimize the environmental impact of the large volumes of manure generated within the watershed is through adjusting feed formulation for poultry and livestock,” the report said.

A new Bay Program strategy for managing excess animal manure in the watershed agrees. It ranked adjusting animal diets to reduce nutrient excretion as its top priority. “This can often save the farmer money and prevent the problem in the first place,” said Kelly Shenk, of the EPA’s Bay Program Office, who led the development of the strategy.

Nutrient pollution caused by excess manure has been a growing problem in parts of the watershed where large numbers of livestock are raised. That’s because livestock operations tend to import much of their food—and the nutrients it contains. Animal farms nationwide often import 50–70 percent of their food.

And much of what comes into the farm ends up coming out the rear of the animal. Animals are inefficient at using nutrients; about 70–75 percent of the nutrients that go into their mouths is eventually excreted.

This results in regional imbalances of manure where more accumulates than can be used. Many farmers who don’t produce animals are reluctant to import manure. In addition, manure often does not contain the right proportions of nitrogen and phosphorus needed by crops—something that has contributed to the buildup of excess phosphorus levels in many parts of the watershed.

Historically, efforts to keep manure nutrients out of the water have focused on such actions as reducing the amount of manure that can be spread on land or fencing streams to keep cows out. But whenever manure is used, it is more likely to run off than chemical fertilizers because it is more difficult to apply, especially during the times of the year when it is most needed by crops.

As a result, many have concluded that the best first step to control nutrient problems from manure is to minimize the amount of nitrogen and phosphorus excreted. “We are trying to prevent the problem in the first place,” Shenk said.

By better managing the food consumed by animals, researchers have shown they can increase the proportion of nutrients going into milk, meat or eggs, and reduce the amount in manure, which becomes a disposal problem.

Interest in reducing nutrients by managing feed began to grow a decade ago when the enzyme phytase was approved for use in farm animals. The stomachs of poultry and pigs cannot easily absorb much of the phosphorus in their feed, so farmers previously had to add extra to make sure the animals were getting enough of the nutrient. Phytase allows the animals to absorb more phosphorus from the feed.

Since then, the use of phytase has become widespread in the poultry industry, The Bay Program estimates that phosphorus concentrations in poultry litter have declined, on average, 16–20 percent.

More may be possible: Roselina Angel, an associate professor of animal and avian sciences at the University of Maryland, estimates that phosphorus reductions of 50 percent may be possible in litter from broiler chickens without compromising the health of the birds.

Not only is the additive effective and relatively inexpensive, almost all of the poultry in the watershed is controlled by a handful of processors who determine the diet for the birds. This ensures that essentially all of the animals get the additive.

But scientists caution that phytase represents about the closest thing in the pantry to a magic bullet—at least for now.

The Bay Program’s manure strategy’s most aggressive goal is to achieve a 20 percent reduction in nitrogen and phosphorus from a third of the watershed’s dairy cows by 2010, and half of the cows by 2015. Securing reductions from cows—the source of a third of all nitrogen and a tenth of all phosphorus from animal wastes—will be more challenging than it is for poultry.

Rather than a handful of large processors controlling the feed, as in the poultry industry, dairy cows are reared by hundreds of independent farmers in Maryland and Virginia—and on more than 8,000 farms in Pennsylvania.

Plus, cows don’t have stomachs; they have four-chamber digestive systems. The first chamber, the rumen, contains billions of microorganisms that break down much of the hay, grass and grains that the animals eat, extracting nutrients that animals with simple stomachs—including humans—could never reach. The rumen is already doing the job of phytase, so the additive does little, if any, good.

“With poultry and swine, you have a single stomach animal where you can feed one ingredient and it makes a difference,” said Virginia Ishler, an extension associate at Penn State University who specializes in dairy feed nutrition. “Unfortunately, with dairy we are trying to feed four stomachs.”

Reducing nutrients from dairy farms means relying almost totally on optimizing the amounts of nitrogen and phosphorus being fed to animals to maximize production while minimizing nutrient output.

Of the two, phosphorus is easier to manage. Many dairy cows have historically been overfed phosphorus, and that phosphorus largely came from added mineral supplements that had to be purchased. “Five years ago, we surveyed the herds in the major dairy regions of the state,” said Katharine Knowlton, an associate professor of dairy science at Virginia Tech University. “Every herd was overfeeding (phosphorus), and they were overfeeding by an average of about 45 percent.”

As more research has shown that those levels of phosphorus are not needed—and only constitute an extra expense for farmers—the rate of overfeeding has decreased, she said. “No research study has ever shown a benefit to overfeeding phosphorus to dairy cows,” Knowlton said. “It just comes out the other end.”

Nitrogen is trickier. It comes in the variety of grains and on-farm forage (grasses and legumes) that are consumed by the animals. The amount of nitrogen in that feed can vary dramatically—and even from week to week. The amount of sunlight and rainfall affects how effectively plants used as feed absorb nitrogen; even the way hay is stored can affect nitrogen concentrations.

Further, the exact mix of feed, and the amount that is home-grown, varies from farm to farm, so there is no one-size-fits-all ration. That means optimizing for nitrogen can mean more frequent tests of feed, which take time and money—things often in short supply, especially on small dairy farms.

And nitrogen, a key building block of protein, is closely related to production. If cows are fed too little, production will drop—and quickly. “If you are doing things incorrectly and you are not controlling what the cow consumes when trying to balance that lower protein level, you can see it immediately,” Ishler said. “You lose production. As soon as a producer sees that, they are going to say this low protein ration is a failure.”

That means achieving reductions from dairy farms, in many cases, means working one-on-one with farmers.

That has been happening in New York’s Delaware County since 1999, where Paul Cerosaletti, a precision feed management specialist with the Cornell Cooperative Extension and his cooperative extension team have worked with a handful of farmers, analyzing—and adjusting—the grains and nutritional additives coming into farms, as well as the forages grown by the farmers. In some cases, farmers have begun to grow more of their feed, thereby reducing imports.

By optimizing diets, farms reduced the amount of phosphorus excreted by a third, while actually increasing productivity, Cerosaletti said. The cooperative extension agents have recently begun working to manage nitrogen in feed, and Cerosaletti predicted “we are going to see as much or more reductions in nitrogen excretions as we have seen in phosphorus.”

The effort is labor intensive. Because feed is so important to production, he said, ongoing contact with the farmers was critical. “We are there working with the farmers on a regular basis, at least once a month,” Cerosaletti said. “When we suggest a feed change, the farmers know we are going to be there to support them in that change.”

The U.S. Department of Agriculture this year has awarded $4 million in “conservation innovation grants” which, along with state and other funds, are helping to test ways to make that happen in other states.

In Pennsylvania, scientists from Penn State, the University of Pennsylvania and the Chesapeake Bay Foundation have teamed to launch a similar effort in which nutritionists will work closely with about two dozen farms a year to optimize feed to reduce manure nutrients in the hope that those producers will become models for others. They also plan to produce and distribute educational information to other farms to promote precision feeding among a broader farm audience.

On a larger scale, Virginia Tech researchers are planning a three-year project that will analyze feeds from 300 dairy farms—nearly a third of the state total—every other month for the next three years. The samples will be examined for nitrogen and phosphorus and other nutrients so that the farmers can better balance the animal rations.

At the end of the first and second year of the programs, farmers who are feeding within 15 percent of the phosphorus requirement will get an incentive payment of $6 per cow; those who feed within 5 percent of the requirement will get $12 per cow, up to a maximum of $4,800 per year.

An even broader outreach method has been devised by researchers at the University of Maryland, who have developed a technique that will allow labs—which routinely test milk from individual farms—to also test for urea nitrogen. All milk contains small amounts of urea, which is not harmful to to consumers, but can serve as an indicator of how much nitrogen is being excreted in the waste.

Grants will partially subsidize the purchase of equipment and of testing costs at participating labs in Maryland and Virginia so they can analyze milk urea nitrogen and report it to farmers, according to Rick Kohn, an associate professor of animal and avian sciences at the University of Maryland. The analysis is a way for farmers to learn whether they are overfeeding nitrogen without doing more frequent tests of their feed, which takes time and money.

Farmers who consistently get results showing high nitrogen levels will likely opt to adjust the diet of their cows, Kohn predicted. “They will save money if they get that lower,” he said, adding that the nitrogen reductions in excretions stemming from the test could be about 10 percent. As an added incentive, the Maryland Department of Agriculture plans to give small payments to farmers who demonstrate reduced nitrogen excretion through the program.

If successful, Kohn would like to see government farm programs purchase testing equipment for other labs in the watershed. The testing equipment costs about $30,000 and associated lab upgrades about $300,000. “With just a small amount of money for equipment, we can get a big result,” he said. After those investments, the actual test will only cost about $1.

While headway is being made, researchers say there are still roadblocks.

A new challenge is the emergence of cheap byproducts from ethanol and alcohol production that are being used to supplement feed. Nutrients are highly concentrated in those byproducts, which easily results in overfeeding.

“These things are great feeds for cows, and they have a lot of energy, they have a lot of protein,” Knowlton said. “Unfortunately, they also have a lot of phosphorus in them. If we did not feed them to cows, we would be putting them in a landfill. So feeding these byproduct feeds to cows is an environmentally sound thing to do, but it has led to a lot of unintentional overfeeding.”

In some cases, she said, dairy farmers who no longer add phosphorus supplements are still feeding 20–30 percent more phosphorus than is needed because of the concentration of nutrients in the distillers grains. “That is going to be a harder nut to crack,” she said, “and it is only going to get more prevalent.”

Although cheap in the short run, those byproducts may prove costly over time. Eventually, phosphorus-laden manure can cause soil—which normally can hold the mineral for long periods of time—to become saturated. At that point, no more manure can be added to the land, creating a bigger manure disposal dilemma for farmers.

Another challenge is working with feed producers and salesmen who often advise farmers. Although feed management is touted as a win-win solution for farmers and the environment, it is not necessarily true for feed producers — especially salesmen who often work on commission. But headway is being made.

“What we are doing is critical, we believe, for the sustainability of agriculture in our region,” Cerosaletti said. “In the long term, it allows the farms to stay around, and reduces the impact of new regulations. We believe the feed industry understands that vision.”

In addition, Kohn said, feed companies are actively researching their own products that will reduce nutrients in manure. While such feeds tend to be cost-prohibitive now, the belief is that environmental concerns will eventually result in a widespread demand for so-called “green” feeds.

In coming years, research will likely yield new ways to achieve further nutrient reductions.

Because the dietary needs of individual animals on a single farm may vary, another possibility is to identify animals with similar feeding requirements and to feed them in groups, allowing the further optimization of rations.

Another promising technique is to optimize feed based on amino acids. It’s not so much the nitrogen that animals need as it is the amino acids within the nitrogen. Amino acids are the building blocks for proteins needed by the animals. One reason an animal uses nitrogen inefficiently is that it typically does not have the right amino acids in the proportions needed by the animals, so the acids are not readily metabolized.

“If you can supply exactly the right profile of the amino acids, then there is less need for inefficiency,” Kohn said. “But that can’t be completely overcome with our current knowledge, and we also don’t have cost-effective methods of delivering the right amino acid profiles to cattle.”

Given time, though, researchers believe that those and other techniques in development could reduce nutrient contents in dairy manure by 20–40 percent. Put another way, when it comes to managing manure, the path to a cleaner Bay may increasingly lead through an animal’s gut.

“We have tremendous potential to reduce the nutrient content for animal waste,” said Tom Simpson, a soil scientist with the University of Maryland and the chair of the Bay Program’s Nutrient Subcommittee. “In the next 5 or 10 years, we will meet and exceed the goals in the manure strategy. I’m very optimistic about feed management.”

Animal Feed Goals

Precision feeding goals set in the Bay Program’s new manure management strategy for different livestock sectors include:

Dairy: Achieve a 20 percent reduction in phosphorus and nitrogen levels in manure in one third of the Bay watershed dairy animals by 2010. By 2015, achieve those reductions in half of the dairy animals.

(Dairy farms contribute about 32 percent of the nitrogen from animal waste reaching the Bay, and 9 percent of the phosphorus.)

Poultry: By 2010 achieve at least a 30 percent reduction in total phosphorus in poultry manure from pre-phytase levels through a combination of adjusting supplemental phosphorus levels in feed and adding phytase.

(Poultry operations contribute about 31 percent of the nitrogen from animal operations reaching the Bay and 26 percent of the phosphorus.)

Swine: The strategy calls on the Bay Program’s Nutrient Subcommittee to develop a plan for achieving manure nutrient reductions from swine operations by July 2007 if science shows reductions are possible without a detrimental impact on animal health and growth.

(Hog operations contribute about 7 percent of the nitrogen from animal operations reaching the Bay and 6 percent of the phosphorus.)