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Feeding Trials Cut Nitrogen Excretion Rates

Article-Feeding Trials Cut Nitrogen Excretion Rates

Iowa State University (ISU) leads a four-year air emissions project funded by the U.S. Department of Agriculture (USDA) conducting animal feeding studies to determine if diet modification can improve air quality around confinement barns. From the swine feeding trials in the first year of the USDA air emissions study, ISU Environmental Specialist and project leader Wendy Powers learned diet changes

Iowa State University (ISU) leads a four-year air emissions project funded by the U.S. Department of Agriculture (USDA) conducting animal feeding studies to determine if diet modification can improve air quality around confinement barns.

From the swine feeding trials in the first year of the USDA air emissions study, ISU Environmental Specialist and project leader Wendy Powers learned diet changes could greatly reduce ammonia emissions in growing pigs.

“Our goal when we started the trial last September (2004) was to try and see how we could reduce dietary crude protein by supplementing with amino acids to minimize emissions,” she explains.

Barrows were placed on feed as feeder pigs and fed to market weights averaging 272 lb. They were given three dietary treatments:

  • A control (C) diet based on lysine that is fed to the majority of pigs in the United States;

  • A low crude protein (LCP), three-amino acid diet (lysine, methionine and threonine) that is being fed by 10-15% of the industry and has been adopted to a greater extent by the poultry industry; and

  • An ultra-low crude protein (ULCP), five-amino acid diet (lysine, methionine, threonine, tryptophan and either valine or isoleucine) that is generally not being fed by pork producers.

Four Feeding Phases

There were four feeding phases. The first grower phase (pigs averaged 54 lb.) included crude protein levels of 22.5%, 20.0% and 18.4% for the C, LCP and ULCP diets, respectively.

As feeding phases progressed, crude protein levels were decreased, explains Powers. By the late finishing phase (pigs averaged 245.1 lb.), crude protein levels were reduced to 16.6%, 15.4% and 13.8% for the C, LCP and ULCP diets, respectively.

Crude protein was dropped 20-25% in the LCP and ULCP diets compared to the control diet. Ammonia concentrations declined 25% in the ULCP group compared to the LCP group, and 36% compared to the C group, she adds.

The dietary study showed no impact on hydrogen sulfide concentrations, nor on the amount of manure produced.

Performance Maintained

Dietary treatments also had no effect on growth performance. “We fed these pigs all the way to market because one of the concerns, from a producer perspective, is whether there are any long-term, negative impacts on performance by feeding these really low-protein diets, such as the five-amino acid diet,” she comments.

Again, while producers are not yet feeding the five-amino acid diets to pigs, that day may come, points out Powers. As demand increases for these products, along with the pressure to reduce air emissions from animal feeding operations, the price will come down. And as the number of amino acids in swine diets increase, there will be a corresponding decrease in the waste margin that occurs from overfeeding nitrogen (protein), according to Powers.

Baseline Emissions Data

In addition to testing rations for developing diets that reduce aerial emissions, Powers says researchers have a second, larger goal of trying to establish baseline emission levels that will be used by the Environmental Protection Agency (EPA).

In early 2006, the EPA is projected to start a two-year monitoring study of more than 2,000 animal feeding operations (AFOs) that signed up to participate in EPA's air compliance initiative. By signing up, farms commit to air monitoring and taking steps to comply with clean air standards. In return, EPA will not sue AFOs for certain violations of the Clean Air Act, although any violations must be corrected.

The four-year project at ISU is also studying feeding patterns for broiler chickens and lactating cows to establish baseline feeding patterns for control of air emissions.

Economic Evaluation

While data collection for the swine feeding study has been completed, the jury is still out on the economic impact. “Emission reduction results are very good. Now it is just a matter of whether producers are willing to absorb the increased cost of the diet,” adds Powers. The ULCP diet costs $18/ton more than the C diet, while the LCP diet costs $4/ton more.

ISU Extension Animal Scientist Ken Stalder says because some producers have grown their hog operations, but not their land base, the economics of diet modification extend from what it costs to feed the ration to how to spread manure on the same number of acres without causing nutrient buildup.

Future Swine Feeding Studies

The National Pork Board has funded a year-long study at ISU, starting next summer, to look at the value of feeding corn co-products to pigs from an emissions and performance perspective, says Powers. Products tested will include distiller's dried grains with solubles; degermed, dehulled corn; and corn gluten meal. The high- and low-fiber rations will be compared with traditional diets.

A full-scale performance study is also being conducted at a commercial hog farm in Iowa. Brian Kerr at USDA's Agricultural Research Service in Ames, IA, is also conducting a metabolism study on corn co-products.

Unique Lab Conducts Emissions Testing

On the outskirts of Ames, IA, is Iowa State University's (ISU) one-year-old emissions testing laboratory.

The building, which formerly housed ISU's swine reproduction facilities, was converted into a unique research lab to study the impact of diet modification and animal/manure management practices on air emissions.

The facility features eight adjoining rooms, 7 ft. wide by 13 ft. long, that can be adjusted to feed everything from pigs to an individual dairy cow to broilers and turkeys.

A goal is to identify specific compounds that correlate to odor, so that diets can be adjusted to eliminate production of those compounds, observes Wendy Powers, ISU environmental specialist and lab director.

Pigs are fed in groups of six/room on a 12-in.-high raised deck that is bolted to a metal structure resembling a mattress frame, she explains. The self-contained structure includes plastic-coated flooring and 50 sq. ft. of penning. Subtracting 2 sq. ft. for a feeder, there is 48 sq. ft. or 8 sq. ft./pig. Manure drops through the slotted floor onto a removable tray for collection. (See photo on p. 12.)

Room conditions are closely monitored to maintain optimum environmental conditions. Probes monitor temperature and humidity in the chambers on a regular basis.

Only fresh air is brought into the facility, tempered during cooler conditions. Air enters each chamber through ceiling inlets, and is exhausted out the front of the rooms. Airflow into each room is measured every 30 seconds to ensure the emissions data is unbiased. Room emissions are sampled 10 or 11 times/day.

During monitoring, a sample of the exhausted air travels through tubing into a manifold, where gases break off into a series of gas analyzers in the adjoining instrument room. Gases measured by the bank of instruments include ammonia, hydrogen sulfide, methane, sulfur dioxide, carbon dioxide and nitrogen oxide. Samples are also sent to ISU's olfactometry lab for odor testing by human sniffing panels.

Computers link researchers to conditions in each room from any location in the world.

In the event of a power outage at the lab, an emergency telephone alarm system continuously dials up to eight numbers until a response is received.

While the current focus of the facility is diet modification and air emissions, ISU's intent was to construct a facility with broad capabilities to meet the research needs of the state's various animal industries, Powers says.

For example, cameras will be added to monitor actual animal activity in the rooms as part of the animal behavior research program being implemented by ISU researcher Anna Johnson.

‘Decision Tree’ Outlines Best Management Practices

Iowa State University (ISU) has built a “decision tree” that provides producers with a tool to help weigh the pros and cons of the best management practices for minimizing air quality concerns.

The database has just been launched, says Ken Stalder, ISU animal scientist. Access the database via

Stalder says the program includes four online, interactive trees for livestock operations and covers:

  • Practices to reduce ammonia concentrations;

  • Practices to reduce hydrogen sulfide emissions;

  • Practices to reduce odor; and

  • Practices to reduce dust and particulates.

When viewing the flow charts, producers choose between liquid and dry manure, type of housing, storage and application practices.

Each practice provides a list of options to address emission concerns, says Angela Rieck-Hinz, Extension program specialist, who developed the Web-based application. The options spell out relative costs (low, moderate or high) and conservative percentage estimates of emission reduction.

At the bottom of each tree are blue buttons that producers can click on for additional reference materials, says Rieck-Hinz.

The materials provide a comprehensive listing of the best peer-reviewed emissions control information available in the United States, adds Wendy Powers, ISU environmental specialist, who helped prepare the documents.

It's a faster way for producers to look anonymously at potential emission control solutions, says Stalder.

The project was made possible by a $47,000 grant from the National Pork Board.

TAGS: Nutrition