How to avoid winter ventilation pitfalls

During winter, swine facilities usually operate at minimum-ventilation rates. But if those rates aren’t correct, high humidity and excess gases will build up leading to increased disease and reduced growth rates, reported Sam Holst, DVM, Swine Vet Center, St. Peter, Minnesota.

“A good understanding of basic ventilation concepts and some routine monitoring to make sure everything is working properly will help set up a barn environment to optimize health and performance while also keeping utility costs in check,” he said. “A lot of ventilation mistakes result from efforts to try to save propane or other utility costs.”

Holst offered several tactics to avoid common winter ventilation mistakes that increase costs.

Calculate minimum ventilation

A big mistake that increases costs and reduces pig performance is an incorrect minimum-ventilation rate.

“Minimum ventilation is the amount of fresh air needed to be brought into the barn to help control humidity and gases like carbon dioxide and ammonia,” Holst explained.

“It’s important to get this correct because over-ventilating will waste propane and electricity leading to inflated utility costs,” he said. “On the flip side, if we under-ventilate, we’ll produce an environment that’s detrimental to health and performance.”

Minimum-ventilation rates should be calculated based on the number of pigs in the room and size of the fans on stage one. Use the following reference charts to help determine the minimum rates. Reference charts for required maximum cubic feet per minute (CFM) per pig and fan CFM output (Figure 1) and  (Figure 2) are helpful for these calculations. (Located at end of article.)

“It’s worth the time and effort to calculate the minimum-speed setting for stage one rather than use an arbitrary setting,” Holst added.

Set heater correctly

During the winter, heater and furnace use increase greatly. Holst stressed making sure the heater is set correctly to achieve consistent room temperature and limit propane waste. He’s seen propane use drop by several gallons per heater per day when settings were corrected.

One costly mistake is setting the heater shutoff temperature too close to the set-point temperature. Room temperature rises even after the furnace shuts off as it takes some time for the heated air to circulate and the probes in the building to detect the increase in room temperature. If the heater is programmed to shut off too close to set point, the room temperature will rise above the set point causing minimum-ventilation fans to speed up and exhaust heated air – essentially blowing recently burned propane right out of the building.

“A good way to finetune furnace settings is to make note of the current settings and watch the room temperature as it cycles through a heater on-and-off run,” Holst explained. “Ideally, once the heater shuts off, the room temperature should rise to just below set point without going over. If the temperature rises above set point, then adjust the heater setting so it shuts off further below set point. In most cases this will be 1.5˚F to 2.0˚F below set point.”

Check temperature probes, fans

All the temperature data fed into the controller to determine ventilation settings comes from temperature probes located in the facilities. If the probes are not functioning correctly, are placed in incorrect locations or are at the wrong  heights, information fed into the controller is inaccurate.

“If that happens, the result is an unfavorable barn environment,” Holst said.

Also, make sure fans are clean and not covered with  debris and dust. Just 1/8 inch of dust will reduce fan efficiency by 40%, he added.

Wrap curtains in plastic

“It can be beneficial to cover curtains with bubble wrap or plastic in the winter to help reduce drafts and heat loss,” Holst said.

His recommendation is to fully cover curtains on the north side of buildings with bubble wrap or plastic. On the south side, cover the curtains up to one foot from where it opens at the top so the curtains can be opened during a warm day.

Following these recommendations for winter ventilation should help keep utility costs in check and provide a healthy environment for pig growth through cold weather, he added.

 

Figure 1.

 

Figure 2.

Ventilation systems need winter check-up to keep pigs healthy

Ventilation systems in hog buildings need regular check-ups to prevent environmental issues that can compromise pig health. Winter audits are especially important, with ventilation running at low levels with little room for error.

“A lot of the winter is spent in minimum ventilation mode,” reported Sam Holst, DVM, Swine Vet Center, St. Peter, Minnesota. “When we do run into ventilation issues, it can be when we are in minimum ventilation, and winter is a good time to monitor that and make adjustments.”

A common problem is moving too much air and chilling pigs, especially in the critical time shortly after weaning. “Pigs will be cold and won’t have the energy to get to the feeder and start on feed,” Holst said.

“On the flip side, if there’s not enough ventilation, humidity will build up,” he added. Gas contaminants like carbon dioxide and ammonia accumulate, causing growth and performance problems. At certain levels, the contaminants can increase respiratory disease and other pathogens in a group of pigs.

Ventilation basics

Many variables go into determining correct ventilation rates. “It is a pretty intricate process,” Holst admitted. “We have multiple barn styles and ventilation systems to start with, and multiple controllers. It’s pretty easy to set up incorrectly and make mistakes.

“Even when I’m on visits for something other than looking at ventilation, there will usually be some issue or adjustment to improve ventilation,” he added. “There’s no doubt it has a big daily impact, and there’s room for improvement on almost every site.”

Minimum ventilation rates are based on the number and weight of pigs in a barn. A reference chart is needed to know how much air (cubic feet per minute or CFM) must be moved per pig per room. Settings to achieve minimum ventilation will then vary, depending on fan inventory and size. Things can go wrong when calculations are not correct.

Incorrect ventilation rate

The first big issue is the efficiency of the fans. Fan CFM ratings are determined at the factory when the fans are new. Fan efficiency takes a hit after being used for several months, and the accumulated dust and dirt aren’t removed.

“A lot of times we overestimate what the output will be in the barn because we are not dealing with factory conditions,” Holst said. “Make sure to clean up those fans with a power washer, and get the dirt off the fan blades and louvers.

“Even 1/8-inch of dust or dirt will reduce efficiency up to 40%,” he added. “That can really throw the ventilation settings out of whack.”

Also be sure to clean fans after fall harvest because extra dirt and chafe will accumulate on them.

Poorly placed temperature probes

“Improper probe location can be another often overlooked cause of ventilation issues,” Holst said. “The controller is getting data from multiple probes, and if they are next to a heater or an inlet, it won’t be an accurate read of what’s going on in the room.”

He recommends setting temperature probes for nursery pigs at 35 inches off the slats and finishing pigs at 51 inches off the slats. In barns with curtains, the probes should be located 5 feet from the outside wall or curtain. In tunnel-ventilated barns, the probes should be located over the areas where pigs sleep most of the time.

Heater issues

When heading into cold weather, all heaters should be cleaned and checked over to make sure they are working. It’s also important to review heater settings.

“The common error I see is incorrect heater settings with the heater programmed to shut off too close to the set point,” Holst said. “Typically, we want the heater to come on 2 to 3 degrees below set point and shut off at least 1 to 2 degrees before getting to the set point.”

If heater shutoff is set too close to set point, the minimum ventilation fans will start up and blow heated air out of the building, leading to higher utility costs.

Blocked inlets

Attic inlets and soffits that are plugged with dirt or chafe also lead to insufficient ventilation.

“If not enough air gets into the attic, then there’s not enough air going into the barn to be exhausted,” Holst said. “You will end up with improper mixing and air exchange.”

He recommends regular cleaning of the soffits and inlets, especially in the fall after harvest.

Fall is also an important time to clean pit fans. “It’s even more critical because a lot of barns are getting close to full manure capacity which can decrease pit fan output,” he added. “Make sure those fans are clean.”

Help solving problems

Producers with ventilation problems that aren’t easily solved can call on veterinarians like Holst to help. He uses several sophisticated meters and data collectors to spot problems in ventilation.

For example, a client of Holst’s noticed an increase in tail biting in a barn and could not find the source. Holst sent a Hobo data collector to the barn where it was installed for a couple of weeks to chart room temperature.

After reviewing the temperature data, Holst noticed the barn at night was not cooling off enough to make pigs comfortable. So the pigs were agitated, leading to increased vice behavior. Without the data collector, he would not have seen the incorrect overnight temperatures.

He also uses meters that measure percent of oxygen, carbon dioxide and ammonia, as well as meters measuring air speed.

“There are a lot of tools and gadgets that I utilize on the full workup that allow me to fine-tune ventilation and find out what’s going on and potential problems,” he said.

Any producer experiencing ventilation issues in hog buildings should contact their veterinarian for help identifying the problems.

 

Inadequate iron supplements cause subclinical anemia in weaned pigs

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The standard 200 mg iron shot for baby pigs at processing may not be enough iron to last until weaning. Anemic pigs at weaning also grow slower in the nursery, reports Sam Holst, DVM, veterinarian with Swine Vet Center, St. Peter, Minnesota.

“The 200 mg injection of iron at processing was the gold standard…We need to relook at [it] to make sure we’re optimizing iron supplementation,” Holst said.

Checking hemoglobin

What he’s learned is no iron protocol works for all hog systems. Using a hand-held hemoglobin reader called HemoCue, Holst conducts diagnostic hemoglobin tests on-site for clients. He usually tests 20 to 30 piglets in a unit right before weaning.

“If we end up with greater than 20% or 30% of pigs iron-deficient or anemic at weaning, then we decide if we need to increase the dose,” he said. “Sometimes we review injection techniques with the staff to make sure [they are] giving a quality dose and not getting iron running out of the injection sites. Or we may decide to administer two doses of iron.”

The most common solution is increasing the dose. Holst sees farms use from 250 mg to 300 mg in a single injection. Going higher in a single dose may cause iron toxicity. If more iron is required, two doses are recommended.

Holst has clients using two doses, especially on farms with extended weaning ages. “If we’re getting out to 23, 24 days at wean age, we really tax that initial iron dose,” he explained. “In those situations, we have gone to either two 150 mg doses or two 200 mg doses.”

Subclinical anemia cases

The iron deficiencies Holst sees are not clinical cases where the deficiency is obvious, such as rough hair coats and pale pigs. Instead, it is subclinical anemia and not visually obvious.

“If we were to identify a group that had some significant anemia issues at weaning, we may go in and inject some iron [right after] weaning to try to catch them up,” he explained.

“There’s been some data that shows piglets that are anemic at weaning will actually grow slower throughout the nursery,” Holst continued. “So if it’s a severe group, it is advantageous to go in and supplement that group.”