By Marlys Miller
Sows leave the breeding herd because they die or are culled, but to advance productivity, animal well-being and financial returns, producers need to better understand why.
“With about 40 percent of female pigs selected for breeding having nine or fewer pigs in their lifetime, there’s substantial opportunity to improve production efficiency,” said Chris Hostetler, animal science director for the Pork Checkoff.
The Checkoff’s Sow Lifetime Productivity (SLP) Task Force and the Pig Survivability Working Group pursue research to learn more about sow productivity, culling and mortality. With much research complete, the SLP Task Force set an industry-wide target of 45 quality pigs per a sow’s lifetime. But to reach that bar, a sow has to remain in the herd, Hostetler said.
About 61 percent of all sow deaths occur immediately before or after farrowing, according to John Deen, DVM, University of Minnesota. The majority of sow mortality occurs in the farrowing room, even with pelvic organ prolapses removed from the equation, he noted.
“One in 40 sows doesn’t make it past the farrowing stall,” said Deen, a long-time sow researcher.
There’s also a bump in sow mortality about 130 days post-farrowing, nearing a sow’s next farrowing event, as the chart (upper left) shows. Bottom line, as for all species, giving birth and lactation place significant stress on the female.
“However, few species put as much body mass and food intake into its progeny as do sows,” Deen said.
“For example, a litter born weighing 35 lbs. could reach 200 lbs. in 23 days, with the gain coming from the sow,” Deen said. “That demands that the sow gets up, eats, drinks, lays down and lactates repeatedly. Anything that inhibits that will challenge the sow.”
Lameness Is No. 1 Risk
Lameness inhibits the sow’s actions, but so do high environmental temperatures, fevers, infection and disease. These factors can cause a sow to go off feed, lose body condition and become infertile, leading to culling or death.
Lameness remains the No. 1 reason why sows leave the herd, accounting for more than 30 percent of culls and the same for mortality.
Even with today’s ventilation and cooling systems, extended summer heat and humidity can challenge sows, particularly when night-time temperatures don’t drop below 70°F for weeks. But lame sows are dealing with two factors that prevent them from getting up and eating.
“Of course, a sow that doesn’t eat has an increased risk of dying or being culled, but the take-home point is that the time off feed doesn’t have to be very long,” Deen said. “Even one day off feed signals a sow’s in trouble.”
Better Culling Decisions
Making better culling decisions can improve sow mortality rates. But culling rates don’t tell you much unless they’re designated by successful and unsuccessful culls, contends Deen.
• A successful cull occurs after a sow has farrowed the targeted number of litters and receives a good cull-sow price at market. Deen estimates that 10 percent of culls are successful culls.
• An unsuccessful cull occurs at an early age or parity or when the sow is sold at a discounted price.
“We don’t put enough weight on when culling occurs,” he said. “Culling after one litter is a lot different than after six. Our aim is to improve the quality of culls by prioritizing pathology throughout a sow’s life.”
Pay Attention to Details
Monitor and record risk factors, such as treatments, disease, off-feed events and lameness, to get a more complete picture of what has brought the sow to the point of culling, he advised.
“Reproductive failure doesn’t occur on its own,” Deen said. “We’re better off culling sows for known pathologies and visible issues versus historical records and also by not making the three-strikes rule firm.”
For example, when lameness is recorded as the sow enters the farrowing barn, Deen has found a greater impact on productivity and mortality than if it was recorded after the sow dies.
“Don’t get too picky about defining lameness,” Deen said. “I ask the person moving the sow into the pen to note anything they detect as being lame.”
Be Specific and Timely
Valarie Duttlinger, a Gentryville, Indiana, producer who serves on Pork Checkoff’s Animal Science Committee, agrees that timeliness and simplicity matter. She cited a farm with 128 reasons for sow removals.
“It was too complicated to assign the loss to the right reason, so workers just picked any reason,” she said. “It’s also important to designate and record the reason when you cull an animal or it dies. It’s too easy to forget later and end up with overly general reasons.”
Finally, sow retention rates to meet breeding and farrowing targets can contribute to sow mortality. While summer mortality rates trend high, it’s not solely due to the heat. It’s also because questionable sows are kept in the herd.
“No question, there is less margin of error with today’s highly productive sows,” Deen said. “We’ve created opportunities for increased reproductive capabilities, but we have to be extra vigilant with management.”