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Articles from 2004 In August

Develop Replacement Gilts Early

There are two keys to efficient gilt pool management: early boar stimulation to induce first estrus, and achieving appropriate weights at first breeding, according to a University of Alberta, Canada research team.

The team suggests the main problem is that producers delay inducing first estrus until gilts reach 180 to 240 days of age, even though replacement gilts are normally quite capable of reaching market weight before 170 days of age.

Delays in stimulating estrus in gilts add to overhead costs and may cause welfare problems if mature sows become too large.

Gilt Study

Groups of Camborough PIC non-pubertal gilts averaging 140 days of age and weighing 133-152 lb. were housed in groups of 20 with unlimited access to feed and water.

The gilts were provided 20 minutes of daily, direct exposure to a vasectomized boar starting at around 140 days of age. Gilts were determined to be “non-selects” or culls if they failed to reach puberty by 180 days of age. “Select” gilts were bred at third estrus, regardless of age or weight.


Provided gilts grew at normal rates (1.21-1.76 lb./day), the researchers found no relationship between growth rates and age at puberty. Inherent differences in age at puberty (early, intermediate, late and non-responders) affected the number of days from first stimulation to first estrus (or designation as non-select), and weight, backfat depth and growth rate at puberty (Table 1).

Figure 1 illustrates the age at which gilts reached puberty. Fifty-nine percent of 509 gilts reached puberty within 30 days of stimulation; 77% gained puberty within 40 days of stimulation, while 23% failed to attain puberty at 40 days of stimulation.

In the study, researchers said an important point for producers to consider is the weight of the gilts considered non-responders at 180 days of age (Figure 2). Overall, 23% of all gilts failed to reach puberty, and nearly 80% were considered above market weight (264 lb. in Canada).

Age and weights at puberty ranged from 132-190 days and 167-331 lb., respectively. Figure 3 provides weight distribution at breeding.

In conclusion, producers need to develop management strategies to minimize the effect of variability in onset of puberty on breeding weight, entry-to-service non-productive days and lifetime performance.

Researchers: Jennifer Patterson, George Foxcroft, Murray Pettitt and Eduardo Beltranena, all of the University of Alberta. Contact Foxcroft by phone (780) 492-7661; fax (780) 492-4265 or e-mail

Table 1. Characteristics Measured at the Onset of Puberty (first estrus)
Item Early Intermediate Late Non-Responders†
No. of gilts 104 161 114 112
Age at Puberty (d)* 148.5a 159.7b 175.3c (>180)
Days to Puberty (d) 8.5a 19.6b 35.2c (>40)
Weight (lb.) 233a 260b 282c 288c
Backfat depth (in.) 0.50 0.54 0.54 0.53
Growth Rate (lb./d) 1.50a 1.60b 1.60b 1.60b
Avg. age of non-responders was 179.7 days at time of removal from experiment.
*Puberty is defined as the first day a gilt exhibits the standing reflex in the presence of a boar.
a,b,cDifferent letters indicate significant differences between early, intermediate, late and non-responders.

New Fertilizer Plant at PSF

Premium Standard Farms (PSF) has broken ground on construction of a revolutionary new fertilizer plant at the Valley View Farm in Sullivan County, MO.

The plant will convert hog manure into a value-added commercial fertilizer using a process developed and patented by PSF and partners to eliminate the use of traditional anaerobic lagoons for manure treatment and storage.

The $9 million fertilizer plant is truly revolutionary because it not only phases out lagoons and captures emissions, it also turns nutrients in swine waste into commercial fertilizer, says Dave Townsend, vice president of environmental affairs at PSF.

The plant will produce 8,000 tons of odor-free, pathogen-free fertilizer a year. The J.R. Simplot Company of Idaho has signed an agreement to buy all of the product from this plant.

The fertilizer plant is to be fully operational by the end of 2004.

Free Management Tool

Murphy-Brown LLC, the swine subsidiary of Smithfield Foods, has developed an environmental management system (EMS) used as a basis for improving conditions at 500 production sites in 14 states.

Smithfield's EMS program gives pork producers a way to design a farm-specific program to ensure that high environmental standards are routinely maintained.

“This is a user-friendly management tool that provides an organized approach to identifying and managing those parts of swine operations that could affect the environment, such as feeding, cleanup, waste treatment systems and spray irrigation,” explains Don Butler, director of government relations and public affairs at Murphy-Brown, Warsaw, NC.

Addressing Farm Needs

Butler says virtually every operation has small problems which, if left unattended, could escalate into big problems. Building foundations crack. Nipple waterers leak. Pipes spring leaks. It's these problems that cause citizens to file nuisance lawsuits and government officials to write regulations, he says.

At Murphy-Brown a few years back, there were problems with some lagoons, he recalls. “We had a problem with trash and foreign materials showing up in the lagoons, including gloves, artificial insemination syringes, pop bottles, you name it. Over time, it became pretty messy out there.” As foreign material falls through slotted floors, pipes become plugged, creating more problems.

When employees were told that they would have to clean up the mess, Butler says some adopted the cavalier attitude that it was just another passing trend. They didn't take the directive seriously.

All that changed one Saturday when all employees were ordered to pitch in to clean up the affected lagoons. From that Saturday on, the problem was solved and staff knew that lapses in environmental management were unacceptable.

The cleanup activity has now been adopted across the entire Murphy-Brown system.

Butler says it is kind of like the carrot-and-the-stick approach. The stick is that everyone must work to fix the problem. The carrot is by avoiding such things as clogged pipes and not having to deal with emergencies, coming to work is a more pleasant experience.

“Now we don't have to wait for bad things to happen and have everybody rush out and try to fix the problems,” he states.

Environmental management has become part of the daily routine. Checking lagoon levels, checking the calibration on the irrigation system and making sure the weeds are trimmed around buildings have become second nature, just like checking feeders.

Under EMS, staff are trained to do the daily jobs and records are kept to verify that the work was done properly and in a timely fashion, says Butler.

“I am a firm believer that if you run a good operation and you get hit with a frivolous lawsuit, by presenting a well-organized approach to environmental management, showing records of routine inspections, training your people and committing to do the right thing, you are going to fare a little better than if you did nothing,” he adds.

The program at Murphy-Brown's has led to fewer notices of environmental nonconformances from state regulators, says Butler.

The 43-page EMS, developed jointly by Murphy-Brown and the North Carolina Division of Pollution Prevention and Environmental Assistance, can meet the specific needs of producers nationwide for an environmental action plan.

Butler says the producer EMS is similar to an ISO 14001 certified program that Murphy-Brown implemented in 2001.

ISO 14001 is an international standard developed by the International Organization for Standards (ISO), based in Geneva, Switzerland. It is a voluntary standard that describes environmental management requirements that must be met to become certified. The certification process is conducted by an accredited, third-party auditor.

The producer version of EMS has been modified to enable producers to more easily adapt it to meet their individual needs.

Butler notes: “There are very good reasons for producers to incorporate sound environmental management practices on their farms: it's the right thing to do, and it demonstrates that swine producers are serious about environmental protection.”

For more information or to get a copy of the producer EMS, call Don Butler at (910) 293-5328. It can also be downloaded from or the North Carolina Pork Council's Web site,

Beware the Dancing Pigs

“Have Peach. Not Pork. A yummy way to watch carbs.”

That's the tagline under the dancing pigs in the adjoining ad. It is brought to you and millions of subscribers of USA Today, U.S. News & World Report (where I saw it) and countless other popular magazines.

The ad, copyrighted by General Mills Inc., the makers of Yoplait yogurt, got me pretty riled up. Do these people even know that pork contains “0” (that's zero!) carbs? The nerve.

How many carbs does a 6 oz. serving of the new Yoplait Ultra Peach Crème yogurt contain, you might ask?

Why, I wondered the same thing. So I hustled on down to the local grocery store and bought a carton. For the record, it contains 8 grams of carbohydrates.

Although you can hardly read it, the ad does point out that “New Yoplait Ultra” has 70% less carbs than their regular lowfat yogurt. Like that makes everything all right!

I wondered if the National Pork Board had seen the ad. A quick e-mail to Dallas Hockman (vice president of the Demand Enhancement group) and Ceci Snyder (nutrition communications director) confirmed that they had. In response, Hockman shared a letter sent to General Mills' CEO/Chairman of the Board Stephen W. Sanger, questioning their flawed motives for the ad and calling it “misleading, inaccurate and inappropriate.”

In the letter, Hockman gives the company the benefit of the doubt, recognizing the company's acknowledgement that both pork and Yoplait's new yogurt product were low-carb options. As the tagline says, General Mills considers theirs to be the “yummy” option.

I saw the ad differently. From my admittedly calloused viewpoint, I thought these guys were taking a cheap shot at pork. My loosely translated rendition of the ad was: “If you want to lose weight, choose our new, low-carb yogurt rather than pork.” The old, tired implication is that pork is fat and it will make you fat. Maybe I'm suffering from a severe case of pork paranoia. But apparently, based on calls fielded by the Pork Board staff, I wasn't the only one who saw the ad that way.

Hockman and Snyder saw the ad as a “huge compliment” to their recent marketing efforts to position pork as a low-carb option. They're probably right.

Hockman's letter goes on to admonish General Mills for the ad's implication that pork is not a tasty, low-carb option, and furthermore, points out that for those watching their carbohydrate intake, pork is a “natural, zero-carbohydrate” choice. And, he adds: “Millions of Americans turn to pork every day because of its versatility and delicious flavor.”

In the letter, Hockman requests that General Mills remedy their advertising faux pas by discontinuing all advertising and sales materials referencing pork, plus a letter of apology to the nation's pork producers, with assurances that steps have been taken to ensure such mistakes will be avoided in the future.

There are two important lessons here:

First, all pork producers must be constantly on the lookout for this type of misleading or inaccurate advertising. Popular publications such as the magazines carrying this Yoplait ad are distributed to millions of subscribers.

Second, never underestimate the need for, or the weight of, a definitive, science-based response such as the one filed by the National Pork Board on behalf of all pork producers. These are your checkoff dollars at work.

New Welfare Lab Offers Pig's-Eye View

Purdue's new USDA Farm Animal Behavior and Well-Being Laboratory, opened this summer, takes a multidisciplinary approach to animal welfare issues.

The new facility, which primarily houses laboratory equipment, covers 2,300 sq. ft. and is adjacent to a 10,000-sq.-ft. laboratory built in 1997. The additional space will allow five scientists in immunology, neuroscience, stress physiology and animal behavior and well-being to investigate swine, dairy cattle and poultry welfare from the animal's point of view.

“Currently, the facility is set to hold 16, 200-lb. pigs in 6 x 6 ft. pens, but we could hold more, smaller pigs in the same pens or we could put in farrowing crates, sow stalls, etc., and make many configurations,” explains Donald Lay, physiologist and research leader for the lab.

The work is aimed at improving current management practices, increasing productivity on the farm, and assisting producers in meeting current and future regulations.

“We're trying to tackle the hard questions related to feelings — pain, frustration and motivation,” says Lay. “These are things that you can't measure, but you can get data that is indicative of various states. The idea is to find out how the animal feels about a situation rather than how we feel about it.

“We want to get away from the idea that humans subjectively decide whether their welfare is okay, and let the animal provide data on these subjective states to allow us to objectively make these decisions,” he adds.

Measuring Fear, Anxiety

Scientists will study swine cognition, fear and anxiety, measuring the levels of the stress hormone, cortisol, in the blood. They'll also study the hippocampus, the part of the brain related to short-term memory and emotional experiences.

Pigs' intelligence and their ability to formulate goals will impact animal welfare. For example, if a sow desires to wallow in the mud, but she can't, she may become frustrated, explains Lay.

Or, if a pig understands that restraint is only temporary, it may feel less stress and be less likely to fight the restraint than if it does not have the cognitive ability to predict its freedom.

Quantifying Hunger

Lay and his colleagues will also attempt to determine whether sows being fed adequately, or underfed, is a welfare issue. In a production setting, sows often exhibit the stereotypical behaviors of tongue rolling, bar biting and excessive rooting. Some suggest these activities indicate that their environment is somehow inadequate.

Researchers have hypothesized that this behavior is related to diet and hunger, since they occur most frequently around feeding time, Lay says. One theory is that these behaviors create more saliva, which buffets excessive stomach acid.

“The issue is, you can be hungry, but it's not a big deal,” Lay says. “Or you can be starving to death, which is a welfare problem. But before you change the management of the diet, such as adding roughage, you need to determine where the animal is on the hunger scale.”

Purdue researchers will measure hunger from a physiological and a behavioral perspective. Lay measures the levels of neuropeptides, the hormones related to hunger, at different intervals. Elevated levels indicate the animal is motivated to look for food.

Satiety, or the state of being fed to fullness, can also be measured with the use of diet pills. The hungrier the animal is, the more diet suppressants are needed for satiety.

Mike Toscano, a PhD candidate, designed a feeder system that requires pigs to push up on a bar, in a rooting motion, to open a door that provides access to food. Once scientists train the 5-month-old pigs to perform the test, they can measure the amount of force the pigs use in accessing food, an indication of how hard they are willing to work for their meal.

Data collected from the study can be used to quantify hunger when food is provided at intervals of up to 36 hours, a common interval feeding regimen.

Studying Controversial Issues

This fall, researchers will study pig transportation and processing, and other topics that may elicit public concerns. Lay believes the U.S. reaction to animal welfare issues will soon mirror those in Europe, where industry standards of livestock management practices have been widely implemented.

“Our group is looking at issues that might be contentious for the public, and ones that producers are struggling with,” he says. “We're trying to come up with solutions before they become a problem. So we're looking at sow housing and tail docking — all those issues that could explode tomorrow.”

The highly controversial sow housing issue will continue to be debated, Lay says. The use of farrowing crates can be justified because they are used for a limited amount of time and they save the lives of pigs. They also provide producers with an economic incentive. Gestation stalls are more difficult to justify to those who are unfamiliar with commercial management practices, he adds.

“Most of the people in the U.S. have no clue how animals are raised, nor where their food comes from,” Lay says. “And when they find out, they are immediately shocked. They want the pigs to be free, but they don't know the implications of that either.”

What the critics don't understand, he explains, is that some sows housed in groups will not perform well. Many will suffer from injuries due to fighting over available space, food and water. And some will have less access to these resources than if they were housed in individual stalls.

In a recent Agriculture Research Service/Purdue collaborative study, researchers removed the back section of the stalls, allowing sows to congregate in an alley. As they studied these sows, researchers found they had more lesions from moving between the stalls and the group area. Interestingly, sow performance did not differ between those sows and their contemporaries housed in closed stalls. Growth rates and coping abilities were higher in pigs from group-housed sows, however.

Tracking Salmonella in Pigs

In addition to the welfare studies, the Purdue scientists are studying salmonella infection in swine to understand how infections increase from 5% in market hogs on the farm to as much as 40% at the slaughtering plant, all in a matter of hours.

Donald Lay at Purdue and Scott Willard, associate professor at Mississippi State University, engineered a strain of salmonella that exhibits the luciferase gene, the gene that emits light in fireflies.

Lay will use the new Purdue facilities to study the movement of salmonella in live piglets. A photon imaging camera will show where bacteria congregate in the body and how swiftly it moves through the animal's digestive system.

Until now, this type of research required killing the animal and looking for signs of salmonella infection in the lymph nodes, tonsils and digestive system.

This new research allows scientists to view the engineered bacteria through a sedated pig at various intervals. The next step will be to refine the process for market weight hogs, possibly using fiber-optic probes to follow the routes of transmission.

PRRS Projects Funded

Nine, one-year projects have been funded in the National Pork Board's PRRS Initiative.

The PRRS (porcine reproductive and respiratory syndrome) projects include:

  • Serum markers of PRRS virus infection, University of Minnesota;

  • Physical characterization of the complete PRRS virus particle, University of Minnesota;

  • Sampling of adult boars during early infection using a new serum collection technique, Swine Vet Center, St. Peter, MN;

  • Development of a killed subunit vaccine, Iowa State University;

  • Design of a new generation of PRRS virus differential marker vaccines, University of Nebraska;

  • Macrophage (tissues that protect the body against infection) cell lines for laboratory propagation of the PRRS virus, University of Nebraska;

  • Implementation of a PRRS virus strain database, University of Minnesota;

  • Development of a porcine adenovirus-based vaccine for PRRS, University of Saskatchewan; and

  • A pilot project for controlling PRRS within a selected region, University of Minnesota.

Swine Flu Still Wreaking Havoc

Swine influenza virus (SIV) continues to plague our swine industry, and the results are often economically catastrophic.

Moderate to severe weather changes, especially in the spring and fall, account for the majority of stresses that trigger the clinical outbreaks of this disease.

We continue to see outbreaks across the Midwest due to this year's unusual summer weather fluctuations.

We have also seen that age holds no limits on the disease. Nurseries, grow-finishers and sow units are all affected, making the “quieting” of the herds much more difficult.

Case Study No. 1

I was called to a 1,000-head finisher with a severe cough and lethargic, off-feed and feverish pigs.

The facility is a totally slotted, double-curtain-sided barn with all-in, all-out (AIAO) production. The pigs weighed about 60 lb. and had been placed in the unit 10 days earlier.

Two pigs died suddenly and a necropsy indicated Streptococcus suis. The pigs were placed on water medication. Diagnostics confirmed the presence of Strep suis. SIV was also isolated from nasal swabs.

The cough continued for 7-10 days with some pigs developing chronic pneumonia and becoming poor-doers.

At closeout, death loss was 3%, while 6% of the pigs ended up as culls.

After the finisher was empty, it was cleaned, disinfected and refilled. Incoming pigs were given SIV vaccine twice, upon arrival and again in two weeks.

Upon further investigation, neither the sow herd source nor its off-site nursery showed any clinical signs of SIV. Further diagnostic tests showed the sow herd to be negative for SIV.

Another finishing unit nearby had broken with SIV recently, so area spread was suspected as the cause of SIV in this finisher.

Case Study No. 2

A 1,200-sow, farrow-to-wean operation experienced erratic farrowing rates for three months, from 65% to a high of 83%.

This 5-year-old unit has averaged 20 pigs/sow/year.

The breeding facilities are excellent, and the breeding management team does a very good job with heat detection and insemination techniques.

The isolation/acclimation (I/A) of incoming breeding stock is done off-site and appears adequate. New gilts and boars are held 45-60 days in I/A before moving into the breeding barn. They are given a prebreeding vaccine prior to movement into the sow unit.

When reviewing the breeding records, the Parity 1 and 2 females showed the lowest farrowing rates, averaging 70%.

Blood tests revealed the herd to be positive for H1N1 and H3N2 SIV, but serological levels varied drastically. This is common in younger animals.

Records indicated early resorption and abortion primarily in the younger females, with a few false pregnancies.

Feed samples were also taken, and zearalenone mycotoxins were found at mild to moderate levels. Feed bins were cleaned out and mold inhibitors were added to sow feeds.

The breeding herd was vaccinated for SIV twice, two weeks apart.

New breeding stock is vaccinated twice while in the isolation unit.

Since this incident, farrowing rates and herd health are improving.


As we continue to strive for better control of SIV, it will demand more stringent measures:

  • AIAO production;

  • Strict biosecurity;

  • Farm-specific vaccination protocols targeting all phases of production;

  • Limited commingling, especially in postweaning phases of production;

  • Altered management schemes as needed to minimize stressors such as empty feeders, ventilation problems, plugged waterers, etc.;

  • Better understanding of various disease actions and interactions; and

  • Proper I/A of incoming breeding stock. Lack of proper I/A and area spread continue to be the primary sources of infection and reinfection.

When viral load becomes high, the disease will often manifest itself.

Due to the immunosuppressive nature of SIV, we often see other disease entities, including but not limited to: Streptococcus suis; Haemophilus parasuis; Mycoplasmal pneumonia; porcine reproductive and respiratory syndrome (PRRS); and other respiratory, enteric and systemic disease complexes.

Every herd's experience with SIV is different due to the various levels of immunity within subpopulations.

Remember, whatever vaccination protocol you choose, the potential for failure exists because of constant changes in strain variation and the growth of mutant strains.

With these developments, commercial and farm-specific autogenous vaccines are our options.

If you are fortunate enough to have a homologous (similar) strain in the vaccine that you are using, then your chance for success is improved.

Work closely with your veterinarian to establish the diagnostic tools and database for your herd.

Ready to Group Sows?

Pork producers looking to switch from stalls to group housing for sows and gilts should scrutinize their options closely.

Most U.S. pork producers still house sows in individual confinement stalls. And there are many good reasons why stalls are preferred over group housing, says Don Levis, director of the Ohio Pork Industry Center, Columbus.

Individual stalls permit proper management of larger numbers of sows; physical aggression, especially during feeding, can be reduced; environment is controlled; more sows are housed in a smaller area; overall hygiene is improved; and herd reproductive performance is enhanced.

Levis says BanCruelFarms (www.ban released an interpretation of 28 scientific papers alleging gestation stalls cause sow suffering.

But he says his experience suggests sows benefit from stalls.

“When I go on farms where there are both stalls and penned gestation, there is consistently a 3-5% difference in farrowing rate in favor of stalls,” says Levis. “And litter size is always a little bit less in group housing.”

Some group sow housing operations wean sows into stalls for 35-40 days, then turn them out into group pens.

Levis has seen problems with group sow housing systems. “In every group system I've seen, whether it be 20 sows or 300 sows in a pen, I can always find a few sows that are really in a high-risk situation. For group housing to work, I think producers are going to have to rethink a lot of management aspects.”

Group Housing Limitations

Levis, in a presentation for the fall Leman Swine Conference in St. Paul, MN, says producers may not be ready to switch to group sow housing.

“Pork producers who house sows in groups manage their dry sows in a group-penning situation without an abundance of scientific evidence to support their management practices.

“Pork producers need to carefully evaluate whether procedures recommended for the design of facilities and management of group housing systems will work for their operations,” he says.

When switching to group housing, staff must focus on identifying and enhancing the welfare of non-competitive sows.

Aggressiveness in group-housed sows can't be stopped because it stems more from sow personality than housing type.

Also, productivity is unpredictable with different stable or dynamic sow groups, where sows are moved in or out periodically.

Proper space requirements for group systems haven't been adequately researched to take into account physical needs and space to act out normal behavioral patterns, says Levis.

Space/sow varies widely in group systems. Housing systems that feed on the floor average 16-24 sq. ft./sow. Systems with individual stalls for feeding and resting provide 24-40 sq. ft./sow. Systems with electronic sow feeders without bedding have 18-32 sq. ft./sow.

The Danes have developed a system that provides 37.1 sq. ft./sow (Figure 1). The T-pen provides 30 sows/pen with individual, lockable feeding stalls; a 14-in.-wide feed trough; solid slotted feeding stall floor; mechanical feeding system; and solid floor bedded resting area.

Number of sows/pen needs to be researched. Currently, the number is determined by the feeding program; sow numbers to fill all-in, all-out farrowing rooms; breeding group; and pen size.

The number of sows/pen ranges from five to 200 head. “Most likely, the establishment of large social groups of sows in an appropriate size pen allows sows to avoid or flee from physically aggressive sows. But the speculation that large social groups of sows reduce physical aggression has not been scientifically evaluated,” observes Levis.

Five Group Sow-Feeding Systems

  1. Floor feeding has been documented to produce the most aggression in the first 30 minutes of feeding.

  2. Group feeding with non-locking individual feeding stalls allows freedom of movement in a large pen and sows are fed on the floor or in a trough.

  3. Group feeding with or without shoulder barriers is a way to possibly eliminate dominant sow aggression. This system features trickle feeding (about ¼ lb./minute) to keep sows in small groups “biologically fixed” in a feed space.

  4. Group feeding with locked, individual stalls is a European design used for a variety of management practices.

  5. The electronic sow feeding system allows sows to be group-housed but fed individually, says Levis.

Waste Handling Innovations

Queen Mary of sludge

A handy, remote-controlled boat removes the risks of measuring sludge depth in lagoons.

The electronic fish-finder nearly fills the inside of Mark Rice's boat — not because the electronics are so large, but because the boat is so small.

The vessel is a remote-controlled model of a tugboat, just a bit longer than a yardstick. The fish-finder mounted inside the boat allows Rice to measure the sludge depth of lagoons without the danger of launching a regular-sized boat on them.

Measuring sludge is a legally mandated imperative in North Carolina where Rice works as a North Carolina State University (NCSU) agricultural engineer. In some states, the tracking of sludge depth is mandated only at problem sites.

“The remote-controlled boat is faster and safer than getting out on the lagoon in a boat,” Rice says.

In about 10 minutes of navigating the boat across a lagoon, Rice takes some 30,000 measurements, backed by global positioning system (GPS) locations. The data is stored on a memory card similar to those used in digital cameras, then plugged into a computer and uploaded to calculate an average depth.

When done by hand, Rice says NCSU recommends a minimum of eight measurements to determine average depth, which certainly would take longer than 10 minutes. Per measurement, those eight hand readings technically would be more accurate, but the fish-finder allows many more points to be measured.

“So you have a much more accurate sludge survey with the remote-controlled boat and the fish-finder,” he says.

Safer Sampling

Rice first raised the question of using a fish-finder for sludge-depth measurements at a meeting where swine company representatives were present. After he began his work documenting the concept's accuracy potential, one swine company began surveying lagoons with a fish-finder mounted on a johnboat.

But Rice felt a remote-controlled boat would better address safety concerns.

“My original concept was to put together common, relatively cheap components that producers could duplicate,” he adds.

A fish-finder with GPS capability costs about $900. The boat can range from as little as $300 to the $2,000 Rice spent to have the model boat completely prepared and the fish-finder mounted.

The university is in the process of protecting Rice's “sludge boat” design from patents or trademarks so it can remain in the public domain. To contact Rice, call 919-515-6794 or email him at

Sludge measurements

A guide to proper lagoon sludge measurements is available from North Carolina State University at:

Separating fact from fiction

Realistic equipment expectations will make your solid separator purchase more successful.

When Jack traded the family cow for magic beans, he didn't get what he thought he was buying. Sometimes, livestock producers suffer the same fate when they buy solid separators to sort their waste flow. Expectations and reality don't match.

The reality about solid separators is they only separate a portion of the solids, says Doug Hamilton, Oklahoma State University waste management expert. Hamilton recently organized a guide to solid separators at the request of the National Pork Board.

“What they should be using solid separators for is making their manure handling easier so the manure will flow down a pipe, or removing the floaters from dairy lagoons or scum from hog lagoons,” Hamilton says.

He adds that standard solid separation, from a purely mechanical standpoint, will not affect nutrient content of the effluent or solids very much. Nor will it make a large difference in sludge buildup in lagoons.

The two basic designs for mechanical solid separators are:

  • screens and filters, and
  • centrifuges and spinners.

Settling basins are a third type, but they won't be covered here other than to note they typically remove about 60% of the solids if properly designed and operated.

Screen separators

The efficiency of screen separator systems is purely logical. How much is removed depends on the fineness of the screen and the type of manure being filtered. “Hog farmers are usually very disappointed when they buy a solid separator,” Hamilton says.

Particle shape and size determines if they will fit through the holes in a screen. Simple gravity is the primary power involved.

Hog feed is so finely ground these days that most hog manure exits the hog as slurry with very fine particles. So, it takes a very fine screen to capture much of it.

For example, a pork producer might catch 50% of the solids with a very fine screen, while a dairy farmer might catch 10% of the solids with a coarse screen. “But the dairy farmer may see a greater effect because it's those stringy 10% of the solids that create most of his headaches,” he says.

This illustrates a very important point about screen-type separators: The finer the screen, the slower they operate.

Most manufacturers have washing or vibrating equipment to deal with this issue, Hamilton says. The simplest screening devices remove an average of 10-20% of the solids and leave them in a rather wet form.

A subcategory of screen separators is the pressure screen. One type forces the manure against a screen, usually with an auger that essentially squeezes out the liquid. Others use various combinations of permeable belts and rollers to squeeze out liquids.

One benefit of pressure screens is they usually present the solids in a rather dry form that is stackable and movable with equipment such as a front-end loader.

The most common pressure-screening device in agriculture is the screw press. On average, screw presses catch 20-30% of solids that pass through them. Results with hog manure might be in the lower end, while dairy manure might be in the higher end.

To get the most from a screw press, the in-flow material must be fairly thick, and the rate of flow may be significantly lower than the machine's maximum rating since it was most likely established using thinner slurry.

Table 1. Characteristics of common solid separators
Device Separation Efficiency (%) Mass Removal Efficiency (%) Cake Total Solids (%) Factors Affecting Performance
Settling Naturally: Up to 65
Chemically: Up to 95
Naturally: Up to 75
Chemically: Up to 95
1 to 3 Influent total solids concentration, Settling time and/or overflow rate
Gravity Screens Naturally: Up to 40
Chemically: Up to 95
Typically: 10 to 25
Naturally: Up to 45
Chemically: Up to 95
Incline: 8 to 22
Vibrating: 5 to 22
Rotating: 5 to 16
Screen opening size, Influent total solids concentration influent flow rate
Pressure Screens Naturally: Up to 40
Chemically: Up to 95
Naturally: Up to 55
Chemically: Up to 98
Screw Press: 20 to 30 Screen opening size, Influent total solids concentration, influent flow rate
Fabric Filters Up to 60 Up to 65 15 to 20 Fabric opening size, Influent total solids concentration, influent flow rate
Decanting Centrifuge Up to 65 Up to 70 25 to 40 Influent solids content, drum speed, auger speed, influent flow rate
Liquid Cyclone Up to 30 Up to 40 Less than 10 Influent solids content, influent flow rate
Source: Doug Hamilton, Oklahoma State University

Other filtering options

Fabric filters function in the same way as screens, although the openings are much smaller so separation efficiency is higher.

A belt press filter uses a continuous belt of filter fabric to move material through the system. Press rollers squeeze moisture from the solids, and a rotary brush removes solids that stick to the belt.

Vacuum drum filters drop the in-flow mixture across a rotating drum made of filter fabric. A vacuum inside the drum draws moisture into it by negative pressure. Solids stick to the filter fabric and are removed from the fabric with a metal edge as the drum rotates.

Media filters use sand or synthetic material to trap solids. They can achieve a high rate of separation efficiency and remove smaller particles than other filters. Thin media filters, such as sand beds, dry as well as separate. Deeper media filters usually perform biological treatment, in addition to separation.

Centrifugal separators

Because centrifuges can effectively increase the gravitational force on particles, and because centrifugal forces can be greater than the earth's gravitation field, Hamilton says centrifuge solid separators can achieve efficiencies approaching that of settling. They also leave the solids, sometimes called cake, dry and manageable.

Two types of separators use centrifugal force: centrifuges and hydrocyclones. Both rotate the solid/liquid mixture and force particles to move to the outside of the rotating motion. In effect, an artificial gravity is created, and particles move by the force of gravity as they do during settling.

Decanting centrifuges are horizontal or vertical cylinders continuously turned at high velocities. Centrifugal force presses solids onto the inside wall of the cylinder. An auger, which turns slightly faster than the cylinder, removes the cake.

Decanting centrifuges can attain high separation efficiency producing semi-solid cake. They require influent total solids concentrations in the 5-8% range, and are considerably less efficient when operated with more dilute influent.

Hydrocyclones are cone-shaped separators with no moving parts. Slurry is pumped into them at an angle near the top of the cone, creating a vortex motion. The swirling motion increases the settling of solids to the bottom of the cone. Liquid leaves the cone from the top.

Separation efficiency of hydrocyclones is not as great as that of decanting centrifuges, but they're fairly good at separating dense particles.

The efficiency of nearly all these separators can be improved by adding one or two chemical agents.

Coagulants are used to cause the particles to coagulate or join together. When manure particles are dispersed in water, they carry a small negative electrical charge that keeps small particles separated. Adding positively charged particles or chemicals to a mixture collapses the negative charges and allows the particles to move closer together.

The most common class of coagulants is salts of positively charged metals such as aluminum sulfate, ferric chloride and lime. Although these substances make the particles stick together, they create a gooey substance that can clog equipment.

Metallic salts are very effective coagulants and, at the right rates, will virtually remove phosphorus from manure slurries through sedimentation. Lime and ferric chloride are caustic and must be handled with care to protect people and equipment.

Some metallic salts are toxic to plants and animals, so they must be used judiciously to avoid problems during land application.

Flocculants are chemicals that bind particles together. Most flocculants used by farmers are organic polymers that carry positive charges.

Flocculants are weak coagulants and are relatively ineffective at removing phosphorus from manure. But, by binding particles together, flocculants create larger particles that are more easily screened. As particle size becomes heavier and stronger, they're more easily removed by centrifugal force.

Polyacrylamide (PAM) is the only commercially available flocculant useable for this purpose. It can increase efficiency of screen filtration dramatically — some research shows up to 95% removal. PAM also improves centrifugal separation.

PAM is non-toxic to plants and animals, and creates strong, easily filtered solids. Cationic polymers are most effective at pH higher than 7.

Although coagulants and flocculants increase the amount of solids settled, they also increase the time needed for a cloud of solids to settle. Chemical coagulants and flocculants can greatly improve the performance of solid separators, but they do it at a higher cost.

Buy big enough

Buy a separator with enough capacity, Hamilton warns. It's critical to calculate flow rates of material passing through the separator accurately, thereby preventing it from becoming a bottleneck in your manure handling flow.

“Outflow must equal inflow. Remember, a solid separator takes a single waste stream and creates two waste streams,” he says.

Forethought and wisdom may be the most important part of the analysis. Solid separation should make handling easier, but it must fit into the manure handling system and timing requirements of the operation, he cautions.

Animal feeders must not choose solid separators based on an arbitrary standard such as percent efficiency, Hamilton says. The most effective system is likely one that combines benefits of multiple subsystems.

Above all, don't forget the cost-benefit analysis.

Irrigation network provides flexibility

An extensive network of irrigation piping lets this Oklahoma hog operation pump effluent and fresh water to 20 center pivots, up to three miles away.

When the Hitch family got into hog production 10 years ago, they wanted more options for applying lagoon slurry to cropland. Their goal was to spread slurry over more acreage, at the times and rates they needed.

Curtis Raines, Hitch Farms manager, and employee Cecil Goetz designed and built a system that ties most of the pivots and wells together and takes effluent from the hog lagoons to the pivots.

Hitch Farms' swine effluent system uses 27 hog lagoons, five portable pumping units, 15 booster pumps, 20 center pivots, 30 wells and 50 miles of underground pipe. It allows more cropping flexibility and makes the timing of effluent pumping less critical.

Raines and his crew manage a variable rotation of corn, wheat, sunflowers and silage corn under the pivots, plus dryland production of wheat in the corners outside the pivots' influence.

“We try to put it on the circles closest to the lagoon,” Raines says, “but if something comes up, we can put it wherever we want it.”

The slurry is 40% effluent, 60% fresh water. An environmental specialist conducts effluent and soil analyses on a carefully regulated schedule.

Hog effluent is the only animal waste flowing through this part of the system. Effluent from Hitch's cattle feedlot lagoons flows into another, smaller system.

A starting place

Five, trailer-mounted, portable pumping units move the effluent. Propane powers the engines. A trailer is parked on the bank of a lagoon and the inlet hose is put into the effluent. Eventually, Raines plans to have a permanent inlet hose at every lagoon to eliminate that step.

A hand-priming device draws fluid into the pump, then the engine is started and the pump activated. Some units have a chopper ahead of the pump. A solid separator puts larger material back into the lagoon through a 2-in. hose.

An in-line meter records gallons per minute (gpm) and acre-feet pumped so operators can record the information for the environmental department's work. A check valve prevents back-flow of freshwater into the lagoon in the unlikely event the engine should shut off.

The pumps have a capacity of 500 gpm but Raines runs them at 200-250 gpm to provide the right amount of flow for the standard mixture of fresh water and effluent to his pivots.

As it leaves the portable pumping unit, the effluent enters the underground system through a portal at each lagoon and is directed to the desired pivot or pivots through the system of pipes, valves and booster pumps.

The 1,000-head finishing houses are mostly grouped in threes, so the effluent from 3,000 hogs goes into each lagoon. Raines says the portable pumps usually stay at each location four to five days.

A web of underground pipes

The underground piping — mostly 8-in. PVC pipe, with some 10-in., and most rated for 50 lbs. of pressure — is the heart of the system. But, three, old, quarter-mile sections with 30-lb. lines are still in the system, so booster pumps are doubly important when water must be moved long distances.

With the area's slope mostly northwest to southeast, that's the general direction of flow for the system. In principle, the system begins with two central lines running from northwest to southeast, with one cross-over point near the high point and many branch lines to pivots and lagoon pumping points along the way (see diagram at right).

Pivots and pumps

For years, Raines has run his pivots at 20-lb. pressures and 500 gpm, but he ischanging nozzles to 700 gpm.

“There were just too many times we couldn't keep up at 500 gpm,” he says. “If we got a little bit behind, or if the transpiration rate was extremely high, especially with corn, we didn't have enough capacity.”

The higher pumping rate will allow application of enough water when irrigation is needed and shut down when it's not. Gypsum blocks are used to monitor soil moisture.

“When the soil profile is full, we shut off the irrigation,” Raines explains.

The 15 booster pumps are indispensable. Some sections of the underground system require low pressure, and friction loss from sending water long distances also can be high.

“My underground water system is really just a reservoir, and I use booster pumps to pick up the water and put it through the pivots,” Raines says. Booster pumps can serve up to eight pivots.

A series of valves at each location allows the water and effluent to be directed where it's needed.

Connections are important

The wells on this portion of Hitch Farms vary from 250-500 gpm. The better-producing wells are on the north and northwest ends, the poorer ones at the southern end, Raines says. All pivots were in place before the swine-finishing units were built. Before hogs, there was some sharing of well water between pivots, but water stayed on the section where it was pumped.

Some states don't allow groundwater to be moved about in this manner. Raines says he's lucky Oklahoma regulations allow it.

The combined piping available for each pivot and the combined use of water for hog and crop production give Hitch Farms options other operations may not have. Raines maximizes water usage through strip-tillage and by limiting irrigation to crop needs. The gypsum blocks used to monitor soil moisture confirm his water conservation efforts.

“My goal is to conserve every drop of water Mother Nature gives me and grow something with it,” Raines says.

Arrested undulations

This Oklahoma pork producer found a simple solution to wave problems.

One very windy day three years ago, Vic Little drove to the lagoon near one of his 3,400-head hog nurseries and was horrified to see huge waves rolling across the surface and crashing against the northeast shoreline.

“It almost looked like you could surf them,” says Little, of Rosston, OK. “I thought about how much those waves were increasing the surface area of the lagoon and how much more odor was coming off it. And also, how much the wave action was stirring it and probably messing up the biological activity.”

Little says his first concern when he got into contract hog production with Murphy Farms in 1998 was odor and its effect on neighbor relations. In fact, Little's emphasis on getting along with neighbors and taking care of the environment earned him an environmental stewardship award in 2003 from the National Pork Board and National Hog Farmer.

“I had to find some way to slow down the wave action,” Little explains.

He first considered large, floating squares of PVC pipe tethered in the lagoons to interrupt wave action, but realized they would be too expensive and cumbersome.

Then he struck upon a brilliantly simple solution. He bought a roll of 1½-in., black polyethylene pipe and cut it to fit the nearly full width of his lagoons. He heated, mashed down and sealed each end of the pipe. Next he drilled a hole through each end of the pipe to which he tied a piece of nylon rope.

Finally, he drove steel T-posts on either side of the lagoon and draped the piece of pipe across and tied it to the T-post on the opposite side. He allowed just enough play for the pipe to float on the surface of the effluent.

It worked perfectly, even on the windiest days.

Little uses just two of these wave levelers on each of his 250 × 325-ft. lagoons. The levelers are spaced so they nearly divide the lagoons into thirds.

“That first one really slows the wave action. Before it can get going good again, it hits the next one. After that, it's not much farther to the edge and it can't get much of a wave going in that amount of space,” Little says. “It's really just a buffer on the surface of the lagoon.”

The banks of Little's lagoons are lined with riprap so bank erosion isn't much of a danger. Many lagoons aren't, so wave action can damage bank slopes and impair the lagoon's function, say lagoon-engineering experts.

Let sleeping sludge lie

Research says old lagoons might best be filled in and monitored.

The old saying that “only the rocks live forever” reminds us that all of our man-made inventions have an end-point. That includes animal waste lagoons.

Most of today's large-scale, animal-feeding facilities are too young to have reached the end of their useful life, yet at some point they will. And, their expiration may pose quite an expense for animal feeders who use them.

An estimate from North Carolina says it costs an average of $43,000/acre of lagoon surface to haul the wet sludge and apply it to land elsewhere. Other states show similar figures.

North Carolina State University (NCSU) is studying an alternative closure method that shows promise. Researchers say unneeded lagoons might be covered with soil and planted to trees to help draw out the moisture, as well as the nutrients. The process, known as phytoremediation, is essentially the same process being used on many municipal landfills across the U.S.

The two lagoon sites in the research project are planted to hybrid poplar trees provided by Ecolotree, an Iowa company specializing in reclaiming landfills and contaminated sites.

Native species of trees may also be considered, but have not been yet planted, says NCSU agricultural engineer Frank Humenik.

Monitoring wells at the sites check for seepage of the nutrients away from the lagoons.

Only one year of data has been drawn from the site, Humenik says, but the second-year data was being gathered at press time. If the process is successful, it could be vitally important as North Carolina is considering the elimination of all lagoons, pending the outcome of a large research project on alternative waste handling technologies.

NPPC Lauds COOL Passage

The National Pork Producers Council (NPPC) applauds the House Agriculture Committee's passage of a bill that would establish a voluntary country-of-origin labeling (COOL) program.

The “Food Promotion Act of 2004” is a bipartisan bill offered by committee chairman Bob Goodlatte (R-VA) and ranking member Charles Stenholm (D-TX). The bill would amend the Agricultural Marketing Act of 1946 to direct the Secretary of Agriculture to establish voluntary labeling of produce, meat and seafood with country-of-origin information.

“The proposed voluntary COOL system is designed to inform consumers without unduly burdening producers,” explains NPPC Vice President Joy Philippi, a Bruning, NE, producer. “We've long supported producers, packers and processors who choose to explore alternative markets to build demand for their products.”