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Audits Return to Basics

Mike Eisenmenger, DVM, has launched a return-to-basics approach to educating producers on ventilation. Many barn offices feature a dizzying array of computer-controlled settings for fans and inlets that attempt to calculate the perfect balance of temperature and humidity and ensure pig comfort. The vast display of ventilation designs faced by field supervisors overseeing contract grower barns can

Mike Eisenmenger, DVM, has launched a return-to-basics approach to educating producers on ventilation.

Many barn offices feature a dizzying array of computer-controlled settings for fans and inlets that attempt to calculate the perfect balance of temperature and humidity and ensure pig comfort.

The vast display of ventilation designs faced by field supervisors overseeing contract grower barns can sometimes be a nightmare.

“It's like all of a sudden they have to learn three or four different controllers,” says Mike Eisenmenger, DVM, Swine Vet Center, St. Peter, MN. “Some barns will have four fans on stage 1, and other systems will have two fans on stage 1. We have all of these different parameters trying to run ventilation, making it difficult for a lot of these supervisors.”

Audit Focuses on the Basics

Eisenmenger's approach is to return to the basics of ventilation management, making sure producers understand the systems they have in place.

He has formulated a four-step program to assist numerous production companies in the Midwest with an audit of their ventilation systems.

An audit has proven especially beneficial in reviewing systems installed during the recent barn-remodeling craze, he says. As barns increased hog numbers, extra fans were often added to boost ventilation rates (cfms/pig) without providing matching fresh air inlets.

Because each system is different, it's also vital to identify the controller being used and build a cheat sheet to ensure employees know how to run it.

Eisenmenger's audit includes these four basic steps to ensure everything works as a system:

  1. Make sure outside air is pulled through the attic. “Honestly, this has been a problem because a lot of older buildings were built with residential soffit material that, over time, gets sealed up with dust, rust and water vapor, which inhibits air from flowing into the attic,” he says. This step evaluates fan power and whether soffits allow air to be drawn into the attic.

  2. Make sure adequate air flows into the room. This calculation includes the number of fans available, cfms/pig and the inlets in the barn. If there are enough inlets, it is important to also check whether they are managed and functioning properly.

  3. Make sure producers know how to operate the whole system, understanding the complete ventilation package.

  4. Make sure environmental conditions are right in the barns. Eisenmenger strongly advises the use of temperature and humidity recording devices to measure room conditions and compare them with barn settings.

Positioning of temperature-recording devices is critical. They must be away from heaters and inlets to get accurate readings. Eisenmenger recommends sensitive temperature probes instead of regular mercury thermometers, which are slow to react and can miss rapid temperature swings. One or two recorders/room is adequate.

Swine Vet Center uses the Temp-Recorder from The Monitoring Company because it is durable, responds very quickly to temperature changes and can be disinfected. Price varies from $90 to $180, depending on level of sensitivity desired.

Program Confidence

Eisenmenger says it's important that the producer or grower “buys into” your barn environmental program so he/she believes your suggestions are sound. To achieve that, he sets up a trial where the producer runs one room in a barn his way and Eisenmenger runs a room his way. Then they compare results.

“The last thing you want is to get in a situation where you tell them how to set the controller, and they follow those recommendations while you are there, but then they switch it back to their method when you leave,” he explains.

Some question whether swine veterinarians are the best resource for ventilation advice. Eisenmenger responds, “I would never claim to be a ventilation expert, but I take an interest in it and try to make it work.”

In fact, he says, swine veterinarians are uniquely qualified to assess ventilation because environment and pig health are closely intertwined.

Mark Stork, nursery supervisor for Holden Farms' 17 contract pig nurseries in southern Minnesota, strongly agrees. “Mike's ventilation auditing experience and advice have helped us a tremendous amount in getting our systems up to code,” he says.

Spotting Ventilation Problems

Eisenmenger says it's easy to spot a ventilation system that's really out of whack — pigs have a bad bout of diarrhea or whole groups of pigs are piled up in the pens. More challenging are the subtle problems caused by drafts, or fine-tuning the environment so pigs do well.

Audits are nearly completed in Holdens' contract nurseries and contract wean-to-finish systems, but fine-tuning continues.

The trick in tweaking systems is keeping the pigs warm, dry, draft-free and comfortable.

For new wean-to-finish pigs, it is important to run the ventilation system just enough to take care of the moisture and the gases so they can lie down on a surface that is 85-90° F without a draft blowing across them, Eisenmenger says.

He paints this picture of a comfortable pig: “He kind of lies next to his buddy, on his side, with his feet out. If he is lying flat on his sternum or piled two pigs deep somewhere, he is not comfortable.”

Finding Comfort in New Barn

Pigs were fairly comfortable one week after arrival at Mike Spindler's new 2,000-head, wean-to-finish barn in early December. With construction work incomplete in one of the two rooms, pigs were double-filled in one room.

This was the first fill of the barn for the former dairyman-turned-contract grower for Holden Farms near Blooming Prairie, MN.

Even though the barn was double-filled, conditions were still challenging for the 19-day-old pigs as a cold snap hit the area. Room temperature was only 58° F when the pigs were placed, reports John Jovaag, who oversees all of Holden Farms' contract grower field staff.

Several key features make placing weaned pigs on 4-in. concrete slats work, relates Eisenmenger. The room features 16 brooder (radiant) heaters hung across two pens that blast out 5,000 btu (low setting) to 17,000 btu (high setting). Two biodegradable floor mats provide ample space for 70 pigs in each of the double-stocked pens.

“This barn is zoned just like a farrowing house; you've got an environment that the pigs really love, and they've got an environment on the mats that is going to be 90-95° F. The zone system reduces propane costs,” Eisenmenger says.

“Pigs urinate and defecate in the cooler area of the pens, grab a bite to eat and come back to the mat area where it is warm,” he adds. “They have a sleeping zone and a living zone, with the whole goal to conserve LP. Air comes in through the inlets and flows into the non-sleeping zone, so we can keep it draft-free and warm in the mat area next to the gates.”

After a few weeks, the brooder heaters and mats will be pulled, leaving the 200,000 btu, L.B. White heaters to provide room warmth when the temperature drops below 76° F, says Jovaag.

The tight-fitting double curtains, enhanced by 4-mil plastic designed to double the R-value of the curtain insulation, provide heat conservation. This extra sheet of plastic will be removed when mats and brooders are removed.

Nursery Family Affair

At the 4,000-head, two-room nursery run by Mark and Lyn Meany and family at Rose Creek, MN, Eisenmenger stressed that minimum ventilation be strictly adhered to with the recent cold snap. “When the temperatures have been nearly 30 degrees below the average for early December, it is doubly critical that we have the minimum ventilation set right on a weaned pig,” he says.

The Meany nursery is a solid-wall barn, so the biggest heat loss will be through ventilation. The goal is to keep the ventilation set low, maintain humidity between 50-70%, reduce heat loss and maintain temperatures on the plastic flooring at 85-90° F for about a week or so postweaning.

When Eisenmenger checked the barn, humidity readings were below 50% and floors were 82-83® F. Ventilation was lowered further to bring up room temperatures.

To check barns, Eisenmenger uses the hand-held RayTec Mini-Temp to spot-check floor and room temperatures and the Thermal Hygrometer from Mannix to measure relative humidity. His rule — if humidity is below 50%, you are overventilating; if above 70%, you are underventilating.

The Meany nursery doesn't use much supplemental heat or mats in regular pens. Pens are stocked with 30 pigs/pen to provide more body heat.

Pens are walked frequently, with fallouts moved to intensive care pens where they get special feed supplements and automatic drinkers. Mats and heat lamps are also provided.

By the time pigs reach 50 lb. and are ready for the finisher, most pens contain 24-25 pigs.

This special attention held mortalities under 1% on the last group of 4,000 weaned pigs.

Holden Farms' contract growers receive weaned pigs commingled from eight Holden sow farms. Pig health has been good because virtually the entire 30,000-sow system is free of porcine reproductive and respiratory syndrome, says Eisenmenger.

Reaching Ventilation Objectives

A barn's ventilation system provides adequate fresh air, keeps toxic gases below maximum allowable concentrations and warns producers of system shutdown.

By Joe Vansickle
Senior Editor

Your ventilation system offers comfort year 'round and helps meet productivity goals, according to Steve Pohl, agricultural engineer at South Dakota State University.

In doing so, ventilation controls humidity, reduces room condensation and lowers moisture penetration through the building's vapor barriers.

Ventilation also affects air temperature, airspeed across animals, dust and disease organisms and odor and gas levels, says Pohl, in a series of Professional Managers Conference talks sponsored by the National Pork Board.

The ventilation system must be designed to match the group size of the pigs being housed.

Realize that the air temperature in a hog barn is seldom the temperature that the pig feels. The pig's effective environmental temperature is basically influenced by those same factors that impact ventilation.

Ideal relative humidity is 50-70% for pig comfort, and to lessen the impact of bacteria, viruses and odors and gases.

Setting Ventilation Rates

Ventilation rates are based on several principles, starting with outside temperature, and including heat control and odor and moisture control rates, says Pohl.

Recommended ventilation rates for minimum (cold weather) and hot weather settings are listed in Table 1.

Pohl points out that recommended mechanical ventilation rates based on cubic feet/minute (cfm) are rising. The norm used to be about 35 cfm/pig with pit ventilation. The curtains could open to exhaust extra heat, but winter winds could cause drafts.

Today, more barns are running 45-60 cfm/pig using mechanical ventilation, with pit fans and wall fans. Curtains don't open until the temperature hits 40° F or higher.

Heating, Cooling Components

Barn environment is comprised of a wide variety of basic ventilation, heating and cooling systems to meet producers' needs in different climactic and production settings.

Pohl uses prevailing weather conditions to determine number and size of exhaust fans needed.

Buy exhaust fans that meet your needs for capacity, efficiency, quality, service and cost.

Air inlets should be placed to provide proper air distribution throughout the room and help maintain proper environment in animal zones, states Pohl. Match inlet size to maximum ventilation needs and ensure they're adjustable.

Whether inlets are sidewall, ceiling, attic or continuous baffle, it's important they provide proper room air distribution at minimum airflow rates, he stresses.

Attic air intake is a crucial part of the air distribution system. There should be 1 sq. ft. of opening for every 400 cfm of airflow. For example, 60,000 cfm divided by 400 cfm = 150 sq. ft. of opening.

Controllers, Sensors

When selecting barn controllers, ease of understanding and operation are the top two factors producers should keep in mind, says Pohl.

Other vital selection criteria include temperature tolerance, number of stages and building/room applications.

Sensors should be placed in a location that represents temperature in the pig space.

Saving Energy

Pohl ticks off a few management lapses that can cause a ventilation system to waste energy:

  • Dirt/dust ▸ in. thick can produce up to a 40% reduction in fan and shutter airflow.

  • Air inlets that are poorly maintained obstruct airflow. Shield exterior winter air intakes from wind.

  • Building curtains that drop several inches at once can produce massive drops in temperature (10-15 degrees). Curtains moving too far too fast are the number one cause of temperature swings in finishers, especially those set on minimum ventilation. Moving curtains too far or too often leads to large temperature swings, says Pohl. Curtains should move no more than 1-2 in. at a time.

Taking Responsibility

Ultimately, the manager of a swine unit is responsible for the environment inside the barn, regardless of initial factory installer settings.

Target specific temperature settings for the controller to follow.

Adjust variable speed fans to mesh with controller settings, and match up variable speed fans with the appropriate motor curves if that function is available on your controller. Determine an acceptable minimum setting and overall operating range.

More information is available at Midwest Plan Service at

Table 1. Recommended Ventilation Rates*
Minimum Hot Weather
Sow & litter 20 cfm/sow 500 cfm/sow
Nursery, 12-30 lb. 2 cfm/pig 25 cfm/pig
Nursery, 30-75 lb. 3 cfm/pig 35 cfm/pig
Finishing, 75-150 lb. 7 cfm/pig 75 cfm/pig
Finishing, 150-250 lb. 10 cfm/pig 120 cfm/pig
Gestating sows 12 cfm/pig 150 cfm/pig
Breeding sows 14 cfm/pig 300 cfm/pig
*Cfm refers to air movement rates based on cubic feet/minute.