Odors from pork operations have become a hot enough issue that it is preventing producers from building new or expanding current facilities. In some cases, neighbors have expressed concern about health issues and property values. Too often the results are lawsuits and regulations. Strict facility setback distances are one such outcome in many states. 

Many techniques to reduce odors are being tested on pork operations. Studies at Purdue University and Pennsylvania State University have focused on the odor source ù the pig.

Since most odors come from manure the pig excretes, changing its diet may reduce odor-causing agents found there. If this works, it would be an easy and, we hope, cost-effective way to reduce odors while maintaining efficient production.

The study involved a typical corn/soybean meal diet fed to grow/finish pigs. Researchers compared the following protein levels:

- A standard 13 percent crude-protein diet.

- A 10 percent crude-protein diet, which is actually protein deficient.

- An 18 percent crude-protein diet (protein excess).

- A 10 percent crude-protein diet supplemented with four synthetic amino acids (lysine, methionine, threonine and tryptophan). 

Researchers analyzed fresh manure from the pigs and manure stored in simulated anaerobic pits. They also took head-space air samples to identify and measure odor-causing compounds.

Reducing crude protein to 10 percent and adding the four essential amino acids cut nitrogen (see chart, top right) and ammonium levels by 28 percent in fresh manure. Those compounds in stored manure were 43 percent lower compared to the standard diet of 13 percent crude protein.

Researchers analyzed more than 40 volatile organic compounds in the air samples. Of that, volatile fatty acids were 50 percent lower in manure from the low crude-protein diet with synthetic amino acids vs. the standard diet. Actually, total volatile organic compounds were lower in the low-protein/amino-acid diet.

In another study, researchers added 5 percent cellulose or 2 percent oligosaccharide (a byproduct of the sugar industry) to a 10 percent crude-protein/amino-acid diet. They compared it to a standard 13 percent
protein diet. Adding cellulose reduced fresh manure’s pH from 7.8 to 6.4. That reduced the chance of ammonia emissions into the air and ammonium excretion by 68 percent.

In stored manure, ammonium dropped 73 percent and consequently so did ammonia (see chart, lower right). Bacterial fermentation increased in the colon of pigs fed the cellulose diet. This is confirmed by increased volatile fatty acid concentrations and lower ammonium nitrogen in fresh manure.

Volatile fatty acids in stored manure dropped when both cellulose or oligosaccharides were added to diets. Pigs fed the low-protein/
amino-acid diet with cellulose had less volatile organic compounds in air samples, creating less odor from stored manure. Sulfur-containing volatile compounds, which can create odors with small quantities, dropped only 12 percent with cellulose added to the diet.

So scientists dug further. They reduced the sulfur amino acids, methionine and cystine, and sulfur-containing minerals, copper sulfate and ferrous sulfate, in the diets.

A 13 percent protein diet was compared to an 8 percent protein diet with additional lysine, threonine and tryptophan. Only methionine was added when necessary to meet National Research Council requirements for the pigs. The copper and ferrous sulfates were substituted with copper oxide and ferric chloride. 

As in previous work, reducing crude protein in a diet and supplementing with essential amino acids
reduced ammonium nitrogen in fresh manure by 45 percent and reduced the pH by more than one unit. Similar responses occurred in stored manure. Volatile fatty acids were reduced by as much as 61 percent in the low-protein/amino-acid diets.

The low-protein/amino-acid diet with copper oxide and ferric chloride

reduced the volatile organic compounds as well. The sulfur-containing volatile organic compounds in air samples declined 63 percent with the low-protein/amino-acid diet compared to the standard diet.

It is apparent that manipulating crude protein,
especially amino acids, carbohydrates and specific fiber ingredients, in pig diets will reduce nitrogen excretion, pH, volatile fatty acids and other volatile organic compounds in the air.

Reducing manure nitrogen excretion means you’d need about 50 percent less land to apply manure ù on a nitrogen basis. Reducing volatile organic compounds results in a reduced odor impact on neighbors throughout the year.

A current negative aspect observed with the diets tested was the cost of certain synthetic amino acids. That could add $1.50 to $2 per pig marketed.

We need additional research to determine fiber inclusion limits, practical sources and cost in the diets.

Alan Sutton is a manure management specialist at Purdue University, West Lafayette, Ind.

He acknowledges the following contributors: Purdue University: John Patterson, O. Layi Adeola, Brian Richert and Albert Heber. Pennsylvania State University: Ken Kephart and Ralph Mumma.


The biggest issue facing Iowa’s pork industry is: Who will regulate environmental matters? As of mid-February, the state awaited an Iowa Supreme Court decision in the case of Goodell & Humboldt County Livestock Producers v. Humboldt County.

In that case Humboldt County adopted ordinances imposing environmental requirements beyond those outlined in Iowa’s 1995 animal livestock regulation act. Among the requirements, the ordinance demands additional permitting and financial assurances.

The Goodells and Humboldt County livestock producers have challenged the ordinances as county zoning in disguise. In that case, the county ordinances would be invalid under Iowa’s agriculture exemption to county zoning and preempted by state law.

A few Iowa counties have adopted ordinances similar to Humboldt County’s, but the Supreme Court imposed a stay on enforcement pending its ruling. Although the Iowa General Assembly reconvened in January, it also awaits the court’s ruling before taking further action. At press time, the court had not yet ruled.

In other news, Iowa’s Environmental Protection Commission initiated new rules regulating confinement feeding operations. They include concrete design and earthen manure-storage standards, which require a minimum 1-foot-thick clay liner and berm erosion-control measures.

County zoning continues to be at issue in at least one county. In November 1996, the Iowa Supreme Court overturned a 1971 case and ruled that confinement livestock production is considered agriculture and thus exempt from county zoning under state law. While some counties are revising their ordinances to comply with this ruling, at least one is  standing by its original°ordinance which imposes setback distances on a confinement sow operation. The matter now is going to district court.

The Iowa Supreme Court also will rule on two cases involving Iowa’s agricultural area law. Under that law, farmland owners may obtain nuisance defense by requesting a county board of supervisors to designate areas involving 300 or more acres as an agricultural area. To receive such a designation and the nuisance defense, land must be used for farming only.

In one case, neighbors are challenging the nuisance defense’s constitutionality. In the other case, a producer who was denied the agricultural-area designation is challenging the county’s action as improper under state law.

Finally, the Iowa legislature will consider many environmental bills. Some would strengthen the manure storage indemnity fund, ban earthen storage, allow counties to zone confinement operations requiring state permits, strengthen Iowa’s habitual-offender law, and appropriate funds to add state inspectors.

Submitted by the Iowa Pork Producers Association.