IMMAG Updates

August 2016

Welcome to the monthly update for the Iowa Manure Management Action Group (IMMAG) Web site. This update is provided as a service to inform you about changes made to the IMMAG Web Page or items of interest dealing with manure management and air quality from animal feeding operations. If you wish to subscribe to this mailing please click here. You may also view this update with direct links on the CURRENT NEWS site on IMMAG.

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The last few weeks of July have been warm and humid. To help keep animals comfortable it’s important to have your ventilation system tuned up. Jay Harmon provides some times in the article “Don’t sweat the heat.” Why are we talking ventilation in a manure newsletter, because we wanted to highlight the AMPAT Pit Ventilation information!

Don’t Sweat the Heat
Jay D. Harmon, Ph.D., P.E., professor and Extension ag engineer, Iowa State University


We normally talk about “bracing yourself” or being at a high level of “preparedness” for winter, but we somehow forget that summer weather can be harder on livestock than winter. Maybe that’s because summer seems like a more relaxed time, for picnics and trips to the beach. Why wouldn’t it be easy on our animals? Two words…. Heat stress!

During the winter we focus on being energy efficient while not chilling the pigs. If we think pigs are cold, we may just turn up the temperature. We don’t have that same option in the summer so we have to be a little more vigilant on making our means of cooling function properly. Much of this system has been sitting, collecting dust all winter and will need scheduled maintenance.  Preparing equipment for hot weather, or for emergencies, can pay big dividends when they are needed. Here are a few things you should think about as we approach summer:

Summer Fans – In some systems, such as tunnel-ventilated facilities, many of the fans were likely winterized with plastic or at the very least set idle for many months. These fans should be cleaned, belts tightened and shutters adjusted to open freely. Fans with dirty blades, shutters or loose belts can move as little as 25 percent of their rated capacity. This impacts cooling of animals a great deal by limiting air exchange and allowing the temperature to reach dangerous levels.
Bandwidths on controller – Bandwidths on controllers can be reduced from 2 F in winter to 1 F in summer, so it is more responsive to warmer temperatures.
Curtain operation – Curtains should operate freely without hang-ups. It is important that pulleys and cords move easily. A curtain that hangs up provides no ventilation. Curtains should also be “trained” to fold up properly. A curtain that bunches up when fully open limits the amount of opening available for ventilation. Grease curtain machines.
Stir fans – Stirring fans should be cleaned and checked for proper operation. Tilt them slightly downward for cooling.
Water lines – Water consumption is very critical in hot weather. Check all nipple and cup waterers, and filters to be sure that flow rates meet the basic needs of the pig.  Check pressure settings. Each waterer should be checked frequently. Flush lines when possible.
Inlet adjustment – Inlets are generally adjusted to direct air across the ceiling in the winter but may point slightly downward in summer to promote cooling. Check adjustment and settings of actuated inlets. In tunnel systems, these should close during tunnel ventilation to prevent hot attic air from entering the barn.
Soffit opening – All soffit openings should be open, not only to provide for mid-range ventilation but also to allow the attic to vent and avoid extreme heat buildup.
Curtain drops/emergency measures – During summer, the possibility of thunderstorms and power outages can be a real danger to livestock in facilities. Check all emergency equipment such as curtain drops and generators on a regular basis. Review emergency plans with employees to be sure everyone knows what should be done in the event of a disaster.
Emergency thermostat – Be sure emergency thermostats on fans are set approximately 5 F above the highest controller setting in case of a controller failure.

Cooling devices are a critical part of the system but a common misconception is that water cools the pigs.  It is actually the evaporation of water that cools pigs, much like sweat cools humans by evaporating.  The combination of air movement with stirring fans, tunnel ventilation or wind, along with a cycling of wetting/drying works best for cooling animals.
Cooling Nozzles – Nozzles used for sprinkling animals may have sediment built up in the line or the orifices may be plugged. Check controller settings. These should be cycled on an off in a manner that allows animals to become dry before wetting them again.
Drip Cooling for sows – Check flow and realign all drip coolers over the shoulder of sows in crates.
Evaporative Pads – Evaporative pads are used most typically in gestation and breeding facilities. Inspect for rodent damage and bird nests.  Be sure the pump is working properly and that drip holes on the inlet tube are free-flowing. Replace damaged pads.  Make sure it is wetting the pad in a uniform way.

Preparing for summer should be taken seriously. Maintenance is important to avoid problems with heat stress.  Heat stress can take a severe toll on the welfare of your animals as well as eat into your productivity and bottom line. For more information regarding ventilation, building maintenance, livestock production systems and air quality, please contact Dr. Jay Harmon at

AMPAT – Pit Ventilation


As you are thinking about your barn ventilation system and how to deal with the summer heat, take the time to consider what pit ventilation does. Buildings with manure storage beneath the floor, often called “deep pit” buildings, generally have concrete annexes in the deep pit wall which are used for pumping manure from the building. Typically fans mounted on the covers of these annexes are used for minimum ventilation. This location is used because it is a relatively easy to mount a fan on the lid and there is a belief that gases will be drawn down through the flooring, thereby preventing gases in the manure storage from entering the animal zone. This is a fallacy disproven by research and, in fact, the pit fans tend to actually increase emission of gases.

To further understand why pit ventilation does not function as many people assume, it is important to understand the physics of pit ventilation, which have been explored by Nicolai and Hoff (2003). In order to get a downward movement through the floor so as not to allow gases to rise into the animal zone a pressure must exist across the floor between the animal zone and the manure pit. In most buildings, 6 to 8 inch slats are used with 1 inch slots which results in a floor opening of 11 to 14%. In order to create a downward draft between 36 and 44 cubic feet per minute per pig (cfm/pig) of ventilation is required. If this is compared to typical minimum ventilation rates for 60 lbs finishing pigs, which is 3 cfm/pig (MWPS, 1983), and weaned pigs, which is 1.5 to 2 cfm/pig, it can be further seen that it is not possible to cause a downdraft during minimum ventilation.

Now this isn’t to say you don’t need minimum ventilation, you certainly do, but as you think about the most effective ways to provide this ventilation fans at the animal level might can be just as effective and help keep emissions of ammonia and odors a bit lower. For more information on this and other odor control strategies check out the Air Management Practices Assessment Tool.

Manure Treatment – Nutrient Separation Technology

Nutrient separation in manure seems to be a hot topic these days. At the recent ag engineering meeting this month there was a session of 12 papers talking about technologies universities around the country, and world, are investigating, and recently the EPA revealed this list of solutions to their Nutrient Recycling Challenge (information about solutions can be viewed here). In the latest manure scoop Dan takes a look at how nutrient separation technology might impact manure management in Iowa, specifically asking the question of how much can the technology cost compared to how well it performs before we should really take a look at it as something we might want on our farm.



The IMMAG Events page is a compilation of manure management related events. Please check the events page often for new listings.

North American Manure Expo
London, OH
August 3-4, 2016
The 2016 North American Manure Expo is schedules for August 3rd and 4th near London Ohio. The show provides a great opportunity to see equipment demonstrations, tour some farm, and hear and see the newest innovations in manure. More information is available at the show’s website.

Livestock Waste 2016
Recent Advances in Pollution Control and Resource Recovery for the Livestock Sector
Galway, Ireland
August 10-12, 2016
The 2016 Livestock Waste conference will be held in August in Galway, Ireland.  The conference will cover policies and regulations on animal manure, pollution control technologies, resource recovery practices, and greenhouse gas emission mitigation. More information can be found on the conference website.

Dan Andersen
(515) 294-4210
Twitter: @DrManure

Angie Rieck-Hinz
(515) 231-2830
Twitter: @iowamanure

Rachel Klein
(515) 294-6685

Melissa McEnany
(515) 294-9075

Iowa Manure Management Action Group

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