January 2021 – Swine Vet Center

January 13, 2021January 13, 2021

Reducing PRRS outbreaks by using air filtration: What you need to know

Jeff Feder, DVM, with Swine Vet Center (SVC), has spent 15 years fine-tuning filtration systems in client hog barns. Today, Feder has records to prove air filtration does reduce outbreaks of disease like porcine reproductive and respiratory syndrome (PRRS).

Looking back over records from 85 farms with filtration, he found these farms prior to filtration were breaking with PRRS over three times more frequently than with filtration.

“Many of the early farms were located in very pig-dense areas and, as a result, were having more breaks with PRRS and other respiratory pathogens than we would like,” reported Feder who works from SVC’s clinic in St. Peter, Minnesota.

“We looked at PRRS break rates to understand if we were moving the needle and changing the number of PRRS breaks…We were able to cut those breaks by a third.”

Explaining filters

Air filtration systems are expensive. Feder said the early ones cost $150 per sow space, but today are at least three times that amount. They can be installed on new and existing facilities.

The filters are key to keeping pathogens out of hog buildings, and Feder has learned which ones are best. Fiberglass filters retain efficiency much longer than synthetic filters. He took used filters of both types out of hog buildings to be tested for filtering efficiency at certified labs.

“Often clients budgeted for those filters to last 2 to 3 years,” he said. “What we found was…the fiberglass filters will maintain their efficiency for a long time.”

Feder also recommends using fiberglass filters with a minimum efficiency reporting value (MERV) of 15 or 16. This means 92% to 95% of the very smallest particles will be removed by the filter.

“Typically, in a filtration system in a pig barn, you have what I call the main filter or end filter, and most commonly those have MERV 14, MERV 15 or MERV 16,” he explained. “Then they have a type of prefilter like the furnace filter in your home. The goal of the prefilter is to take out the large dust particles so those particles don’t plug up our expensive end filters.”

Impact on existing ventilation

Most of the filtration systems used by SVC clients are retrofits put on existing ventilation systems in hog barns.

“One common scenario in the top-down ventilation system is to simply install the filters over the top of the ceiling inlets, and that is your point of filtration,” Feder explained. “In tunnel-ventilated barns, you build filter banks in front of the cool cells before air enters through the end of the barn.”

Other modifications may be needed to accommodate air filtration. Often existing fans don’t move as much air as before the filters were added due to higher static pressure. Keeping fan shutters and blades clean may be enough to increase their efficiency. Otherwise extra fans can be installed to boost airflow.

When cool cells are involved, Feder recommends making sure they work correctly and are on a timer. Airflow filtration is reduced when water is running through the cell pads.

Negative versus positive pressure

Most existing hog facilities are negative-pressure ventilation systems, according to Feder. Some new buildings with filtration use positive-pressure systems.

“The benefit of the positive-pressure system, at least in a filtration scenario, would be if there are any leaks in the barn, those leaks are getting pushed out so it’s filtered air being pushed out,” he explained. “On the flipside in negative-pressure systems, if there are leaks, it’s unfiltered air leaking into the barn and that’s not a good thing.”

While the positive-pressure system sounds better, he cautions that ventilation rates run higher which can lead to higher LP usage rates in colder climates. In addition, there’s more potentially contaminated air being pushed into the barn, which could be a problem.

“Negative-pressure systems run at much lower ventilation rates in the winter, but we do have to worry about leaks,” Feder said. “We’ve spent a lot of time over the years figuring out how to build them tighter with different construction ideas using foam and caulk…to get these barns very tight.”

Air filtration works

“I completely believe in filtration and think that it’s a good tool to use, especially if you’re in a pig-dense area,” Feder said. “I would just caution, though, that it’s like any other tool that has to be managed.

“Along with filtration come some additional things that need to happen. Make sure we’re monitoring the performance of the filters, looking for air leaks on farms and we do all the other things for biosecurity correctly as well.”

January 13, 2021January 13, 2021

Top-notch gilt management requires attention to details

The basics of managing gilts for optimum pig production and longevity are well known. But successfully applying them requires meticulous attention to details, according to Jake Schwartz, DVM, Swine Vet Center.

“The best farms really embrace the details and make sure they’re executed 7 days a week,” Schwartz said. “That’s the difference between average farms and great farms.”

There are some basic rules he recommends for ensuring gilts realize their full genetic potential and become prolific members of the sow herd.

Disease management

The first is managing disease threats like porcine reproductive and respiratory syndrome (PRRS), which can derail gilt performance. Schwartz suggests either keeping PRRS out of the herd or finding an appropriate way to handle it in a herd.

“[If] PRRS management strategy involves vaccine or serum exposure, the timing of those two events is important,” he said. “Do exposure early in the gilt’s life so when she farrows the first time, she’s not giving birth to PRRS-positive pigs.”

He also recommends avoiding PRRS exposure around time of breeding or right after breeding to prevent reproductive issues like mummies and abortions.

Parvovirus type 1 also causes reproductive issues with gilts, including increased rate of mummies, especially when they’re exposed for the first time post-breeding. All gilts should be vaccinated pre-breeding. If there is an elevated rate of mummies, there are some creative ways to get parvo exposure pre-breeding and minimize its impact.

No breeding on first heat

One breeding rule tops the list of production techniques for optimum gilt management. “It’s been well documented that when we breed an animal on her first estrus, we give up total born and farrowing rate,” Schwartz said. “Proper gilt management includes heat-no-servicing and breeding on a second or third heat.”

This rule is in place because a gilt’s uterus is still developing during first estrus and not quite able to handle a large litter, he explained.

Also remember not to equate gilt age with sexual maturity. “Some animals will cycle for the first time when they are 24 or 25 weeks of age. Others will cycle for the first time when they are 30 or 31 weeks of age,” he said. “It’s kind of a bell curve.”

Acclimate gilts early

Another technique for good gilt development is making sure nothing occurs to throw a gilt off feed in the 14 days prior to breeding. This means vaccinations should be completed and the gilts moved to their stalls at least 14 days before they are bred, Schwartz explained.

“Both of those things will, in some animals, throw them off feed around the time of breeding,” he said. “Then in subsequent farrowings, those gilts will have less pigs.”

Early estrus equals longevity

Time of puberty can be a trait used for gilt selection because gilts coming into heat early usually are the most prolific in the herd.

“When an animal comes into heat early or is one of the first third or half…we know those gilts tend to be more long-term, prolific members of the herd versus a gilt that first comes into heat at 30+ weeks for the first time,” Schwartz said. “Those gilts tend to be more short-term members of the herd and have lagging total born and farrow rate.”

The ideal gilt management program would select females that cycle by 30 or 31 weeks of age and younger. “In a perfect world, that’s what you would do,” he explained. “But unfortunately, given the constraints of some of the system’s farms, that’s often not the case.”

January 6, 2021January 18, 2021

SVC Newsletter – December 2020

Ventilation fundamentals to optimize pig performance

Air quality and barn temperature are two of the most critical environmental components that effect pig health and performance. Poor ventilation increases disease and reduces growth rate by creating a barn environment high in humidity and excess gasses. Many ventilation mistakes are the result of efforts to save utility costs. This month Dr. Sam reviews some fundamental ventilation concepts that will help set up a barn environment that both optimizes pig health and performance while keeping utility costs in-line.

Minimum ventilation

Minimum ventilation is the amount of fresh air needed to be brought into the barn to control humidity and gas contaminants (i.e., carbon dioxide, ammonia, etc.). Accuracy with minimum ventilation settings is crucial as over-ventilating will inflate utility costs (propane and electricity) while under-ventilating will produce an environment detrimental to pig health and performance.

In most barns, the fans assigned to minimum ventilation are variable speed fans which have two important settings – minimum speed and bandwidth. Minimum speed is a controller setting that signifies the speed at which the minimum ventilation fans will operate at any time room temperature is below set point. When the room temperature rises above set point, minimum ventilation fans steadily increase speed until the maximum speed is achieved. The number of degrees for variable speed fans to go from the minimum speed setting to 100% is called bandwidth. Bandwidths can be widened or narrowed based on ambient temperatures, number of fans, pig size, motor curves, or other factors that impact pig comfort.

We recommend minimum (stage 1) bandwidth settings of 1.5-2.0°F. A bandwidth setting of 1.0°F or less is too narrow for most barns and will increase fan speed too quickly, potentially chilling pigs. Wider bandwidths (above 2.0°F) reduce the ability to efficiently remove heat from the barn.

It is important to note that the setting on the controller does not necessarily equate to the percentage of maximum cubic feet per minute (CFM) output by the fan. For most variable speed fans, there is good alignment between controller setting and CFM output between 75-100%. However, the reduction in CFM output is disproportionate to the reduction in minimum speed controller setting at 70% and below (Figure 1). Most variable speed fans will produce 50% of their maximum CFM output with a minimum speed controller setting between 55-60%.

Figure 1. Variable speed fan output vs minimum speed controller setting

Minimum ventilation needs are calculated based on the number and size of pigs in a barn. Controller settings to achieve the needed minimum ventilation are dependent on the number and size of fans on stage 1. Take the time to calculate the minimum ventilation rate needed rather than set minimum ventilation fans at an arbitrary minimum speed. Reference charts for fan CFM output (Figure 2) and required CFMs per pig (Figure 3) are helpful for these calculations.

As an example, consider a 2400-head wean-to-finish barn receiving newly weaned pigs. Minimum ventilation needs are 3600 CFM (2400 pigs x 1.5 CFM/pig). If stage 1 consists of 1 x 24-inch variable speed pit fan, 60% of the maximum CFM output would be required for minimum ventilation (3600 CFM needed ÷ 6000 CFM max output x 100). Therefore, a minimum speed controller setting of approximately 65% would be needed to obtain 60% of the maximum CFM output (Figure 1).

Keep fans clean – it is essential to routinely clean exhaust fans. Even an 1/8 inch of dust or dirt can reduce fan efficiency by up to 40%. This will significantly alter the minimum ventilation settings required to attain the correct barn environment.

Temperature probes

Ventilation controllers rely entirely on temperature data received from multiple probes located throughout the pig space. If probes are placed incorrectly, the controller will receive inaccurate readings resulting in incorrect controller operation and barn environment.

Recommended height and location of temperature probes varies by barn type and stage of production (Figure 4). Make sure to adjust probe height between nursery and finisher stages in wean-to-finish barns. Probes should be positioned away from ceiling inlets and heaters to avoid artificial fluctuations in temperature from cold or hot air.

Figure 4. Recommended probe height and location

Heaters

Improperly set heaters are a surefire way to waste propane and skyrocket energy expenses. Like variable speed fans, heaters also have two primary settings to consider- offset and differential. The offset is the number of degrees below set point that the heater shuts off. Differential is the number of degrees that the heater will run. Adding the heater offset and differential together determines the number of degrees below set point that the heater will turn on. For example, with a set point of 80°F, heater offset of 2.0°F, and heater differential of 1.0°F, the heater would turn on at 77°F and run until the room temperature reached 78°F (Figure 5). Some controllers have simplified these settings to “heater on” and “heater off” temperatures.

Figure 5. Example heater and minimum ventilation settings

Setting heater offset and differential correctly are keys to achieving consistent room temperatures and limiting propane waste. The most common problem found in barns are furnaces that shut off too close to the setpoint temperature. In these cases, room temperature rises even after the furnace shuts off as it takes some time for the heated air to circulate and the probes 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 ramp up and exhaust the heated air to cool the room – essentially blowing recently burned propane right out the exhaust fans.

A suggested heater offset of 1.5°-2.0°F and differential of 1.0°F are good starting points. Understand every barn is different based on the number and size of furnaces in a room as well as the cubic feet of room to heat. An effective way to fine-tune furnace settings is to make note of the current settings and observe the room temperature as it cycles through a heater on and off run. Ideally, after the heater shuts off the room temperature should rise to just below the set point without going over. If the room temperature rises above set point, increase the heater offset so that the heater shuts off further below set point. Correct heater settings can reduce propane use by several gallons per heater per day resulting in significant energy savings.

Summary

Barn environment has a substantial impact on pig health and performance. Incorrect minimum ventilation, probe placement, and heater settings will be detrimental to both pig health and performance. Understanding and implementing these ventilation fundamentals will help maximize performance and control utility costs.

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