November 2020 – Swine Vet Center

Lameness is now the leading cause of mortality in mid- to late-finishing pigs. How did lameness develop into such a big problem?

Mike Eisenmenger, DVM, Swine Vet Center, and Kathleen Wood, DVM, Christensen Farms, addressed the lameness issue during a recent webinar produced by the Swine Health Information Center. Both shared insights from their experiences managing lameness in finishing hogs.

First, pathogens that used to drag down finishing pigs are under control. “We worked really hard to remove the major pathogens that flow out vertically from sow farms,” Eisenmenger reported. “We want to be able to give the nursery-grow-finish system PRRS- (porcine reproductive and respiratory syndrome) and Mycoplasma hyopneumoniae-negative pigs so we can get the lowest mortality possible.

“In reality, even though mortality has improved, it seems we hit a baseline threshold. It is getting harder and harder to make continuous improvements…and there are a multitude of reasons.”

Lameness caused by bacterial arthritis has become the big reason for mortality today. Eisenmenger credits the infectious “small bugs”— Strep suis, Mycoplasma hyorhinis and hyosynoviae, Actinobacillus suis, Glaeserella parasuis — for the arthritis.

25% to 40% lameness new normal

Industrywide, lameness affects 10% to 25% of hogs in grow-finish. But Wood was stunned to see how much lameness increased during the COVID-19 shutdown.

“It has been on the upward trend in the summer months,” Wood said. “Recently 25% to 40% severe stiffness or lameness is not uncommon. Lameness is the No. 1 cause of mortality in our mid- to late-finish hogs. Unfortunately, it has become the new normal.

“Mild lameness has always been there,” she continued. “We just weren’t recognizing it as an issue because it doesn’t raise red flags as a cause of high mortality. Stiffness and subtle lameness aren’t alarming, and they don’t trigger the need for immediate treatment in the industry. But we need to change that. We need to start reacting to low-level mortalities.”

Back to basics: necropsy it

A focused, coordinated effort to reduce lameness by Christensen Farms started with the veterinary team going into the field and regularly working with service staff on necropsies to help identify causes for stiffness and lameness.

“Our service team is very well trained, but there are still nuances and additional things that they can learn about on causes of lameness and post-mortem exams,” Wood explained. “We started cutting open a lot of pigs with them and getting our team to open pigs on their own. They weren’t confident cutting open joints, so we walked it through with them.

“It’s not always about just the heart, lungs or brain,” she added. “If a pig can’t walk properly, it’s chances of making it to market as primary pig has severely decreased. This means that getting into the bones and seeing what’s going on is an obvious but underlooked necessity.”

The results of the additional training are a game changer for Christensen Farms, she added. It reset what the farm’s service teams expect with lameness.

“Pigs are not supposed to be stiff,” Wood said. “Lameness and stiffness are not normal. Pigs are not supposed to be in pain when walking.”

Treat early signs

The second part of the Christensen Farms plan involves early recognition of lameness, with a priority placed on treatment.

“We have to do what’s right for the pigs,” Wood said. “Treat them. We are limited in our options, especially with anti-inflammatories. But they are equally as important as antibiotics and give pigs pain relief. In our system, we are limited to two, and there are withdrawal times that make it difficult to use them in late-finishing pigs.”

To help caregivers identify when to treat, Wood created a chart with photos of pigs showing three stages of lameness, with the required treatments. The chart helps farms quickly identify when help is needed.

Work with diagnostics

Another part of the lameness fight means working closely with the diagnostic lab. Wood wants all lameness samples sent to the lab with a detailed history and other communications of the problem to help the lab more quickly find the cause.

Also, samples sent to the lab should be the entire limb and not be fluid from an open joint. Conditions in the barns are not sterile enough to collect the fluid, according to Wood.

Other interventions

Wood also works with other departments at Christensen Farms to determine the best treatment options. For example, she suggests working with the marketing group if 5 days are needed to provide medication with a withdrawal time to get on top of a lameness issue.

Another department that can help with lameness issues is nutrition. “Nutritionists are your friends, not enemies,” Wood said. “Ask them what we can do to make this better and be open to their suggestions. Spending time with them in the field is a great way to get aligned on the issue.

“And don’t forget the sow farm,” she added. “What are they selecting for on confirmation? What can we do to knock down their bug load? How about maternal immunity? Everything goes downstream.”

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.

Month: November 2020

How to tackle mortality-causing lameness in finishing hogs