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2005 Swine Research Review - Manure/Odor Control

Herd Health/Management The Impact of PRRS On Cost of Production Four pork industry analysts used a combination of techniques and data to project the current annual cost of porcine reproductive and respiratory syndrome (PRRS) to the U.S. swine industry. The USDA-National Animal Health Monitoring System (NAHMS) conducts a survey every five years to provide a valid demographic and descriptive survey

Manure/Odor Control

Organic Mineral Cuts Excretion Rates, Maintains Performance

Bioplex organic trace minerals can be utilized in the diet at much lower rates than inorganic minerals, decreasing excess mineral excretion, without impacting growth performance.

That was the finding of a team of Iowa State University researchers who measured performance and growth rates on over 500 pigs in two trials.

Today's large swine systems have generated environmental concerns because concentrations of manure can lead to mineral depositions that exceed crop nutrient requirements.

In the study, grow-finish pigs were assigned 10-12/pen to four dietary treatments. Treatment 1 was a control diet containing a common trace mineral supplement, while treatments 2-4 contained Alltech's Bioplex products at 100%, 75% and 50% mineral supplementation rates, respectively.

Fecal samples were collected from each of the treatment groups, and live performance and carcass measurements were both recorded.

Pigs fed the control diet ate slightly less feed than the three experimental groups. But there were no differences observed in live performance for average daily gain, average daily lean growth on test or efficiency of lean gain, or in overall performance and carcass traits.

Fecal analysis showed that the control diet pigs excreted much higher levels of copper across four diet phases. Pigs on trace mineral supplementation with Alltech's Bioplex at the 75% rate excreted less copper than pigs fed at the 100% Bioplex level.

Iron was excreted at much higher rates by the control group pigs than the Bioplex-supplemented pigs.

Zinc was also excreted at much greater levels by the control group pigs. Zinc was excreted at much lower levels by the pigs fed the lowest level of Bioplex.

Overall, the lowest level of Bioplex appeared to provide the most advantage of the three experimental diets in lowering overall mineral excretion levels when compared to traditional trace mineral supplementation.

Researchers: J.L. Burkett, K.J. Stalder, C.R. Schwab, W. J. Powers, T.J. Baas and J. W. Mabry, Iowa State University. Contact Powers by phone (515) 294-1635, fax (515) 294-5698 or e-mail

Reducing Ammonia Volatilization from Swine Manure

Several management strategies hold promise as ways to reduce ammonia volatilization from swine manure.

The laboratory experiment at Iowa State University studied the effects of six types of management strategies on the volatilization of ammonia and nitrogen content of swine manure during short-term storage.

Table 1. Percent Difference in Post-Storage (24, 48, 72 and 96 hours) Slurry Nitrogen (N) Composition and Headspace Ammonia-N Concentrations Compared to Experimental Controls
Treatment Slurry g./100 g. Percent of TKN1 Ammonium-N Headspace Ammonia-N mg./square meter
Urine + feces
Urine alone -80% -84% -99%
Feces alone -77% -73% -99%
Unaltered pH (6.59)
Acidified (pH 5.3) -9% -8% -75%
Alkalized (pH 8.85) +10% +11% +778%
No urease inhibitor
Single dose NBPT2 NS3 NS +48%
Double dose NBPT NS NS +130%
No nitrogen binder
Single dose yucca NS NS -14%
Double dose yucca NS NS -28%
Room temperature
75° F
95° F +11% +18% +18%
108° F +40% +40% +805%
Continuously stirred +5% +4% +115%
1Total Kjeldahl nitrogen
2N- (n-butyl) thiophosphoric triamide
3Differences were not statistically significant.

Fresh manure was collected from grow-finish pigs and diluted 1:1 with water. Twenty-four sealed vessels made of PVC pipe were filled with 1 qt. of manure and had 1 qt. of headspace where ammonia and other gases accumulated.

Treatments included modification of storage temperature; continuous agitation; addition of a urease inhibitor, N- (n-butyl) thiophosphoric triamide or NBPT from Agrotain International; a nitrogen-binding product (De-Odorase, Alltech Inc.); segregation of urine from feces; and pH manipulation.

Duplicate vessels were used for each combination of treatment and storage time. After 24, 48, 72 or 96 hours of storage, the ammonia concentration of the headspace was measured. Storage time effects are not included in this report.

Data from each trial are reported in Table 1.

Segregation of urine from feces showed great potential for preventing both production of ammonium-nitrogen and ammonia release. Separate storage of urine and feces reduced release of ammonia into the headspace to less than 1% of the amount measured when feces were mixed.

Acidification to a pH of 5.3 decreased ammonium-nitrogen concentration by 9%, and the total Kjeldahl nitrogen in the form of ammonium by 8%, while an increase in the slurry pH to 8.85 resulted in increased headspace ammonium concentration.

The yucca extract, De-Odorase, reduced ammonia volatilization in a dose-dependent manner without affecting ammonium-nitrogen concentration, and also prevented the ammonium from being released into the headspace as ammonia.

The urease inhibitor, NBPT, did not effectively reduce ammonia concentrations in the headspace.

Warmer temperatures and continuous agitation of the slurry both increased slurry ammonium-nitrogen concentrations and ammonia volatilization.

Overall, segregating management of urine and feces is the most promising strategy for preventing ammonia volatilization at the point of excretion.

Keeping manure slurry cool, unstirred and at a low pH could help prevent or slow ammonium formation. Adding a nitrogen-binding product (such as De-Odorase) could then reduce the amount of ammonium-nitrogen volatilized as ammonia.

Researchers: D.M. Panetta, W.J. Powers and J.C. Lorimor, Iowa State University. Contact Powers by phone (515) 294-1635, fax (515) 294-5698 or e-mail

Phytase Reduces Phosphorus Excretion By Weaned Pigs

Excess phosphorus (P) in the diets of weaned pigs can lead to manure application concerns.

The use of phytase enzyme allows pig diets to be formulated with less total P, decreasing P output in manure and potentially reducing feed costs.

The impact of excess P is reduced when dietary calcium (Ca) to P ratios are above 1.7:1.

Two experiments at the Prairie Swine Centre in Saskatoon, Saskatchewan, looked at the effects of Ca:P ratio on phytase efficacy and the influence of the phytase enzyme on P excretions.

In the first experiment, dicalcium phosphate was added in levels up to 2,000 units/kg. of phytase enzyme to achieve different concentrations of total P in the diet; 500 units/kg. is typically the recommended addition level.

Added phytase produced a modest improvement in growth rate, but no effect on feed intake, and therefore, no improvement in feed efficiency.

Total excreted P ranged from about 4 g./pig/day when dicalcium phosphate was added to the diet, to 2.1 g./pig/day when no dicalcium phosphate was added.

Also, the P excreted as soluble inorganic ranged from 75% to 80% of total P and was not affected by treatment. Therefore, adding phytase to the diet decreased excretion levels of total P.

The benefits of adding phytase to the diet were also achieved in the second experiment, which also showed that the effectiveness of phytase is reduced at Ca:P levels above 1.7:1.

In short, the addition of phytase enzyme to weaned pig diets resulted in about 1.4 g./pig/day less P excreted compared to the same diet with an inorganic source of P.

Researchers: Denise Beaulieu, John Patience and Mike Bedford, Prairie Swine Centre, Saskatoon, Saskatchewan, Canada. For more details, contact information specialist Ken Engele by phone (306) 373-9922, fax (306) 955-2510 or e-mail

Three Systems Tested for Hydrogen Sulfide Exposure in Barns

Exposure to hydrogen sulfide gas during manure management practices can pose harm to workers and pigs alike.

Prairie Swine Centre (PSC) engineers developed and tested three systems to alleviate those concerns.

A remote manure pit plug-pulling system allows the worker to pull the pit plug from outside the building using an extended core plug, cable and cable winch system.

In nine plug-pulling events tested at two grow-finish barns at PSC, the level of hydrogen sulfide gas was 68 ppm in the room, while concentrations at the winch were 0 ppm.

Due to the water-soluble nature of hydrogen sulfide, a second trial examined a system to spray water on agitated manure to reduce aerosol emissions. Using a hollow nozzle cone at 200 kPA (kilopascal), water was sprayed into barrels filled with swine manure. In four control barrels where no spray was applied, manure agitation produced an average of 148 ppm hydrogen sulfide with a peak reading of 520 ppm measured from the exhaust air.

When the water spray treatment was applied, hydrogen sulfide concentrations increased to an average of 273 ppm at the barrels and 690 ppm in the exhaust air.

Laboratory tests of the water spray method had consistently reduced gas concentrations released into the chamber. More tests are being conducted to assess the failure of the water spray treatment.

Finally, using a scraper blade to remove manure daily from a grow-finish room dramatically reduced hydrogen sulfide gas levels, by an average of 80% over the plug area and by 96% over the middle pen, in comparison to a control room. Scraped manure drained into a sewer line at both ends of the barn.

Also in this study, hydrogen sulfide concentrations exceeded the 15 ppm ceiling occupational exposure limit (OEL) three times for the non-scraped rooms, compared to no times for the scraper room. The ceiling OEL is the maximum concentration of a biological or chemical agent to which a Canadian worker may be exposed.

Researchers: Bernardo Predicala, Stephane Lemay, Claude Lague and Shala Christianson. For more details, contact information specialist Ken Engele by phone (306) 373-9922, fax (306) 955-2510 or e-mail

Chemical Process Converts Hog Manure to Oil

Laboratory batch process studies have shown that swine manure can be thermochemically converted to an oil product using hydrothermal processing.

The oil product might be suitable for on-farm use for boilers for winter heating, or if further refined, used as a bio-fuel for combustion engines.

The crude oil could also serve as a starting material for a number of petroleum-based products.

For the project, fresh manure was collected from pen floors of the Swine Research Center growing facility at the University of Illinois.

The manure was processed into a slurry of about 20% solids content, ground to reduce particle size, and then heated under pressure.

The continuous hydrothermal process (Figure 1) consists of a high-pressure slurry feeder, a process gas feeder, a continuous-stirred tank reactor, a products separation vessel and process controllers. It has the capacity to process 106 lb. of slurry/day and has run for 16 hours continuously in tests.

Highest oil yield of 70% (based on volatile solids content of the manure) was achieved with processing temperatures of about 572° F and pressure of about 1,500 lb./sq. in. (psi). Slurry was processed for about 80 minutes.

The addition of carbon monoxide in the process did not improve the oil yield, but did produce a more fluid oil product.

Carbon and hydrogen content of the oil were recorded at 63% and 10%, respectively.

An on-farm-integrated system could reduce on-farm manure storage needs by continuous processing of manure, minimize environmental impact and produce an economically viable product.

Researcher: Yuanhui Zhang, University of Illinois. Contact Zhang by phone (217) 333-2693 or e-mail