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Agricultural Engineer Steve Pohl

Swine building designs evolve over time, and with those changes come a whole new set of rules in environmental management. But one thing producers need to remember is that despite those structural changes, the basic rules for proper ventilation never change, observes 61-year-old Steve Pohl.

To help spread the word on swine building ventilation, Extension agricultural engineer Pohl from South Dakota State University (SDSU) at Brookings, joined by a cast of engineers and animal scientists from Iowa, Minnesota and Nebraska, including swine consultant Mike Brumm, have taken the show on the road. Ten traveling workshops have been conducted around the Upper Midwest with a fully equipped mobile ventilation trailer.

Through his 25 years at SDSU, understanding the basics of ventilation have become virtually a campaign for the soft-spoken Pohl, who becomes highly charged as he attempts to explain the intricacies of air movement through swine barns.

At the ventilation workshops and classes he teaches, the discussion centers on the three keys to all ventilation systems: controllers, inlets and fans. “We show them the interaction of the three and how if one is out of balance, it can mess everything up,” he says. Three principles are therefore crucial for ventilation systems to operate smoothly:
1. Controller settings must be adjusted correctly to match the weight of the pigs, optimize pig performance and not waste energy.
2. Many large barns today rely on a series of ceiling air inlets, which need to be properly sized and adjusted to provide fresh air distribution in the room.
3. When all fans are operating, but still not providing adequate fresh air flow, it’s usually because of inadequate attic air intake.

“Matching adequate attic air intake with inlets that are properly matched with fans means that everything works out,” Pohl says with his patented broad smile.

However, if there isn’t adequate air intake or ceiling inlets to meet fan capacity, static pressure can increase substantially, and ventilation is again out of whack, he says. Put another way, static pressure rises when air flow is restricted, and fans have to work harder to try to provide proper ventilation and remove heat from the barn. The result is that energy bills rise and the performance and health of the pigs could be compromised.

Those problems are magnified in curtain-sided barns where it’s difficult to maintain a balance between a warm room environment with a cold, windy day and still properly manage ventilation when curtains open too quickly.

During a workshop, air flow meters and other measuring devices are demonstrated to help producers, technical service staffs and others understand proper swine barn ventilation settings.

With changing building designs and technologies, ventilation systems continue to become more complex, but the rules of ventilation remain the same, he reiterates.

At the end of the day, checking air flow and speed across the animal and determining how the animal is reacting in these systems will pretty much tell you about pig comfort.

Although Pohl spends much time in workshops and classrooms breaking down the barriers of misunderstanding about ventilation, his job is obviously much broader. He has a full plate as a full professor working out of a cramped office in the Agricultural and Biosystems Engineering Department. His assigned duties include agricultural structures and environment, housing, farmstead and grain storage systems planning, waste management and providing technical support to various private and public groups.

He also conducts research on how the environment affects livestock production.

Tenuous Career Track

The Rosholt, SD, native’s career didn’t exactly start out headed toward agricultural engineering. He was raised on a dairy farm in the extreme northeast corner of the state, graduated from the local high school and decided to become an electrical engineer.

Pohl was following the advice of a friend, but was also encouraged by relatives not to stay on the family farm. “Part of it was just the economics and the fact that the farm wasn’t large enough (a 15-cow dairy and 560 acres of cropland),” he explains.

Attending SDSU was a big deal for a small-town kid. The first year went fine, but the second year turned sour and he left at the end of his sophomore year to take a six-month hiatus back on the home farm.

“We were in the process of moving to a 50-cow dairy when the barn burned down,” Pohl remembers, ending any thoughts he had of becoming a dairy farmer. The farm was converted to a 4,000-head poultry farm.

Pohl returned to SDSU in the spring and decided to switch majors to agricultural engineering. The plan worked well, and he received both bachelor’s and master’s degrees. He received his PhD from the University of Nebraska.

One of the main reasons that changing his major worked was the influence of Mylo Hellickson, his graduate advisor, who was very supportive, and remains one of the experts in ventilation systems to this day. He offices next door to Pohl.

Varied Career

Pohl, who believes strongly that agriculture does not get the recognition it deserves for providing food for the world, also raves about the “phenomenal amount of ways” to enjoy a career as an agricultural engineer, from building structures to environment, to natural resources and manure management.

His early occupations are a testament to that versatility. Following graduation in 1975, he received two job offers, one from the Amana Refrigeration Co. in the Amana Colonies in Iowa and a second from the University of Nebraska for an Extension position at the Northeast Station at Concord. He took the Nebraska job as a district agricultural engineer working on conservation systems and livestock facilities.

Pohl worked next to Bob Fritschen — “the enthusiastic swine guy at Concord” — who taught him the ropes about Extension and was a leader in development of the Nebraska monoslope and popular modified-open-front hog barns. Their downfall was that they were run as continuous-flow production systems and ventilation was misunderstood; the difficulty in managing partially slotted facilities sealed their fate, Pohl says.

As inflation climbed, pay at the university didn’t keep up, so Pohl elected to try a job in industry. He went to work for Great Plains Supply Co., based in St. Paul, MN, where he served as a field engineer working out of a home office in Brookings, SD. The company built livestock confinement barns and modular, ranch-style homes. His job was to design agricultural, residential and light commercial buildings for over 100 lumberyards from Williston, ND, to Manchester, IA. He specialized in designing trusses and beams.

But the extensive travel, poor management decisions and the farm crisis of the early ’80s sent building sales plummeting. He left Great Plains and worked in a series of different jobs over the next three years. His first stop was as an engineer at James Basin Builders in Aberdeen, SD, in 1983-84; next he became territory manager at Lester’s of Minnesota in 1984; then he served as a sales engineer at Enercept Building Systems of Aberdeen in 1985-86.

Returning Home

Pohl says he got the best advice of his career from SDSU staff, when he applied for and got his current job as an agricultural engineer at the school. “Louie Lubinus was in this position from the later 1940s until 1984. He was retired at the time, but he told me this was the best job in South Dakota. I would have to say he was pretty close to being right,” Pohl declares.

He fondly recalls the past quarter century of working with cattle, dairy and hog producers. “Early on, we did a lot of Extension meetings, but also a lot of farm visits, probably averaging about 100 farm visits a year,” he says. There were more farmers to advise and a lot of interest in remodeling projects, since most farmers didn’t have enough equity to finance new construction.

Design Changes

In the early ’90s, building designs shifted to totally slotted confinement barns, and moved away from modified-open-front barns, and other partially open hog structures in an effort to improve pig health. But those early, multi-site production systems required that pigs be moved from phase to phase, and hog diseases often went along for the ride, he says.

Today’s hog systems have fewer moves and less disease transfer, but continue to pose ventilation challenges, which requires an understanding of the controllers and the overall management of the ventilation system.

But that challenge isn’t as daunting as the structural problems caused by 80- to 100-ft.-wide buildings being able to withstand snow loads. “The problem is, when it snows out of the north, a lot of it piles up on the building and we get a load at a particular point of the barn. It has probably caused more structural failures than anything,” Pohl says.

Back in the ’70s, buildings were designed to handle 20 lb. of snow per square foot very comfortably. “In today’s world, if we don’t design for 30-40 lb. per square foot,” he says, the chance of building failure has increased due to the amount of snowy winters the Upper Midwest has experienced in the last decade.

Environmental controls in these newer buildings have become more sophisticated as systems have become increasingly mechanically ventilated. “They can be easier to operate as long as the ventilation system is properly designed and managed. But remember, you can have all of the sophistication in the world, but you still have to understand the basics of ventilation,” Pohl stresses.

Air Filtration Frontier

Another challenge for agricultural engineers such as Pohl, who has been a leader in the design and construction of air filtration systems for hog barns, is how to maintain proper ventilation and keep out the PRRS (porcine reproductive and respiratory syndrome) virus.

“When Dr. G.F. Kennedy from the Pipestone (MN) Veterinary Clinic and I first started working at converting boar studs, I knew filters were going to be restrictive (to ventilation), and from the commercial-application filters that were used (in hospitals), there would be problems with the increase in static pressure,” Pohl explains.

The light bulb came on for Pohl when he figured out that the filters would have to be sized larger to reduce static pressure and match up with the current barn fans. “We knew we couldn’t run our barn fans against this kind of pressure because airflow capacity would be reduced considerably, and fan motor maintenance increased,” he says. Airflow rates for a 24 x 24-in. filter assembly were reduced from 2,000 cfm down to 600 cfm, vastly reducing static pressure.

The success of the boar studs in providing proper ventilation and filtration and restricting the PRRS virus has now spread rapidly to sow units, with similar results. The next frontier may be wean-to-finish units, but Pohl cautions that there may be additional filtration and biosecurity hurdles to overcome before those units are retrofitted.

Pohl is quick to share credit for the success of air filtration. “Dr. Scott Dee’s research has been a key to this whole thing and the promotion of filtration. I just filled in the engineering side,” he says in his humble way.

The South Dakota engineer says contrary to expectations, the cost of air filtration systems hasn’t dropped since they were first installed five years ago. In fact, as filtration systems have become more commonplace, their cost has increased as more refinements have been added to exclude all possible introductions of unfiltered air into the hog barn.

With lower airflow rates, it’s vital to match filters with fan capacity in filtered hog barns, Pohl points out. “Sometimes you may have to add more filters to lower static pressure, or add more fans to match those two components, so it is going to cost you more. But if you want to safeguard health, you may have to pay more for your buildings to get there,” he says.

Partial air filtration systems have been installed on a few farms, but Pohl believes the risk is greater than the reward.

In the future, Pohl expects hog barns to become more mechanically cooled. “Our barns run too warm the majority of the year, actually,” he says, “so if we can come up with some way to keep these barns at a cooler temperature during warm and even mild weather, there may be some significant advances in average daily gain and feed efficiency. As our feed costs continue to rise, we may want to cool pigs more to make them more efficient,” he adds.
Boar studs cool animals, as do a few production units, to keep room environments at a constant temperature.

Helping, Teaching, Learning

Pohl says as the swine industry must reinvent itself to survive spikes in production costs, so too must Extension staffs at universities. “The university staffs need to learn to network — interact with the people they are trying to serve,” he says.

He credits all of his experience and knowledge to the farmers he continues to serve in South Dakota. “Producers try a lot of stuff, and their farms are the greatest labs in the world,” he proclaims.

Helping those producers and teaching students daily are the most rewarding parts of his job at SDSU.

And working at the university has opened many doors for the small-town native, from traveling to China to learn about that giant country’s swine industry, to visits to the U.S. Congress in Washington, DC, and seminars around South Dakota learning about the various aspects of agriculture in his home state.

Besides his duties at SDSU, Pohl is co-owner and chief financial officer of Rural Technologies, Inc. (RTI), based in Brookings, along with Chris Chase, an immunologist at SDSU. RTI is a contract research company that works with pharmaceutical companies.

Pohl and his wife Kathy have two children. Son John is finishing up his economics degree at the University of Minnesota in Minneapolis, and daughter Laurie attends the University of Iowa in Iowa City, working to become a physician’s assistant.