Virulent PRRS outbreaks in grow-finish require fast action to cut losses

A particularly difficult variant of the porcine reproductive and respiratory syndrome (PRRS) virus recently hit hog farms in south-central Minnesota. Henry Johnson, DVM, with Swine Vet Center in St. Peter, Minnesota, was called to diagnose and treat the PRRS outbreaks on client farms.

The virus has been identified as PRRS 1-4-4 and, to date, is the most virulent PRRS variant to infect hogs in the US.

“More herds have gotten infected, and this PRRS strain seems to be extremely pathogenic and more prone to airborne transmission,” Johnson said.

When it affects grow-finish units, he recommends immediate and aggressive treatment to reduce mortalities.

First symptoms

“When you walk into a PRRS 1-4-4 outbreak, you see a lot of pigs with varying degrees of respiratory challenge,” Johnson explained. Often, he sees pigs “thumping,” where the animals labor to breathe through airways blocked by bacterial and viral pneumonias.

“Other times, pigs are very, very lethargic because PRRS attacks and disables the whole immune system in pigs,” he said.

An outbreak can be identified early if grow-finish units are tracking water consumption. Pigs will quit drinking first, causing a dramatic drop-off in water usage. This should signal the need to start intensive pig care immediately, Johnson noted.

These symptoms may affect 5% to 25% of the pigs, depending on where they are in the disease challenge.

Diagnose, separate sick pigs

Johnson’s first action is to gather samples and send them to a diagnostic lab. The PRRS virus strain needs to be verified, and secondary bacterial infections identified.

“Get good bacteriology and susceptibility information from the lab, so you can make better microbial decisions and have confidence that you are putting the right medication for the right bug and utilize it appropriately,” he said. “It’s also good, judicious antibiotic use.”

At the same time, he wants to be aggressive and get help started for ailing pigs. He recommends moving critically ill pigs to sick pens for individual care.

“The best thing to do is provide a warm, dry, comfortable area with less pressure and competition for feed, water and space,” Johnson said. “Pigs can recover and subsequently move back to the general population where they are mixed in with other pigs. Then you can cycle other pigs through that sick pen.”

Another immediate action should be to increase barn temperatures, especially for young pigs. Pigs rarely die from being too warm in the winter during the nursery phase but can die of complications from being too cold.

Suppress secondary bugs

“A lot of times with these nasty PRRS [outbreaks], you are already behind the eight ball when you start,” he said. “You will never cure viral disease with an antibiotic. You are just trying to suppress secondary bacterial infections and control them when the immune system is devastated and rebooting after going through the PRRS infection.”

Depending on the herd and challenge, Johnson said they will use different antibiotics and delivery methods. He recommends starting water medication right away to address common secondary bugs like Streptococcus Suis, Glasser’s disease, Mycoplasma hyopneumoniae and Pasteurella.

When pigs are unable to get up to drink, Johnson recommends a mass injection followed by oral antibiotics or water medications.

“A lot of focus for me is to make sure we use the right antibiotics and follow up with caregivers to make sure the pigs that need help are moved and getting the necessary care,” he said.

Even with these care regimens, mortalities can still be high. He estimates as much as 15% mortality can occur.

Biosecurity alert

“When you get a virus that is really severe like this and spreads quickly across multiple production systems and geographies, it is a wake-up call to biosecurity practices in grow-finish,” Johnson said.

If any labor or equipment is shared, make sure all parties involved know what is going on. It’s also good to keep the feed mill in the loop as well.

“It’s a hard culture to establish, but if you are able to reduce a break like this, it demonstrates the importance of keeping our barns clean,” he said.

 

 

 

Lowering pre-wean mortality starts at day 1

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Pre-wean mortality continues to be a challenge to producers across the industry as genetic improvements allow sows to be more prolific and achieve higher total born. As a result, producers face the difficult task of reducing mortality rates that are as high as 15% on some farms.

A big part of the solution starts with a focus on the first few days of a piglet’s life when roughly 50% of pre-wean mortalities occur, reports Henry Johnson, DVM, Swine Veterinary Center, St. Peter, Minnesota.

Day-1 focus

“It all ties back to day-1 care and getting those pigs started right,” Johnson said. “You really want to identify piglets that are cold, in the corner or isolated and don’t have a belly full of milk. These are no-brainers, but it’s really hard to do consistently on the larger farms today.”

There’s pressure on farm employees to be fast and efficient when checking over litters and still catch all the problems.

“That’s what makes it a challenge, especially on farms dealing with a lot of labor shortages,” Johnson added. “But once [employees] get to a level of understanding what it takes to be successful from day 1, that’s where we see the best farms really start to excel.”

After day 1, the focus continues on managing the smaller, left-behind pigs, often with the use of a nurse-sow system. Johnson says they do a lot of two-step nurse-sow collections, which usually involves a newly weaned sow to nurse a younger litter from a donor sow. The donor sow is then available to nurse the youngest, poor-performing piglets.

Bump in gestation feed

Gestation feed also affects piglet weight at birth and the ability to thrive.

“Farms that are most successful are the ones managing feed correctly at the beginning and end of the gestation period to avoid those low birthweight pigs,” he said.

“It seems to have an effect when we increase feed intake the last 2 to 3 weeks of gestation. [We are] just trying to add some extra ounces on those piglets right before they farrow.”

Important metric

During visits to client sow farms, Johnson focuses on the farrowing house and pre-wean mortality rates.

“It’s definitely a metric that all our clients are looking at every day, every week and comparing from farm to farm,” he said. Good farms strive to be under 10%. Really good farms target 8%, and farms with challenges will be 12% to 15%, he added.

On farms with challenges, it is difficult to lower the mortality rates because there are many possible scenarios and causes. It also requires a lot of employee training to help “understand what risks are presented to those young pigs and how to mitigate them through the farrowing house,” he explained.

But clearing these hurdles to lower pre-wean mortality rates pays off. Few metrics have a bigger impact on the bottom line than this rate. Saving one or two more piglets per litter means more market hogs out the door.