Who isn't looking to boost sow productivity? It's a topic that industry specialists revisit time and again. After all, everyone wants more pigs or more parities per sow.

The place to start is to focus on gilt development and sow condition, say pork production experts polled across the country.

Gilt development protocols in the United States are not optimal for the reproductive female, says John Mabry, director of the Iowa Pork Industry Center. "We've taken a lot of fat off these females and some of the leaner maternal lines don't reproduce as well. That's had an impact on overall reproduction."

When the National Pork Board-funded maternal-line project was completed in 1999, one significant finding was that sows lose backfat every time they farrow, even while they are still growing. "Breeding gilts carry as much fat as they will ever have in their lifetimes," reports Rodney Goodwin, National Pork Board director of production research.

Producers may not have been receptive to gilt development strategies back in 1997 when the maternal-line studies began, adds Goodwin, but they're paying attention now.

University of Tennessee Extension specialist Ken Stalder, who was involved in NPB's gilt- development research project, says you should avoid maximizing lean-growth accretion in developing gilts. "The objective is to build fat reserves. A slower, flatter lean-growth curve is conducive to getting gilts into proper body condition and be reproductively prepared to enter the breeding herd."

Stalder completed a net-present-value analysis that shows sows need to stay in the herd until third or fourth parity to guarantee positive returns over their lifetimes. "Many sows barely reach that point," he says. "They exit the herd just when they reach a profitable parity. Herds that are run that way will not be sustainable long-term."

Parity distribution has put a crimp on productivity, the experts agree. "Not enough good gilts get into parities three, four and five," says Purdue University reproductive physiologist Wayne Singleton. "When sows would be ready to really pop out pigs in the fourth parity, there aren't enough sows left."


"Some gilts are being bred too early, plus poor sow condition and lactation feed intake are making them drop out of herds far too soon," says Singleton.

Then there's the feed-intake issue, a problem in many farrowing houses. "The first five to seven days are critical to get hormones started again," says Don Levis, Ohio State University Pork Industry Center coordinator. "Too many people think they'll crash sows, so they work feed intake up too slowly."

Levis adds that this can be the consequence of labor challenges and inexperienced labor. Farrowing-room feeders should be checked within three hours after the morning feeding, he points out. (The table on page 21 lists his feeding recommendations during lactation.)

Kansas State University's Mike Tokach agrees that no more than 20 percent of feeders should be empty in the farrowing house at one time. Simple things like counting empty feeders can help ensure that feed is in front of sows.

"Sow condition has a lot to do with mortality rate," continues Tokach. "Changes in body condition from one farrowing to the next and missed meals in gestation or lactation, sets sows up for ulcers or other intake-related problems, and it can affect mortality. Low backfat also contributes to developing lameness and shoulder sores."

The Kansas State nutritionist is looking at ultrasound as a means to adjust feeding levels during gestation so sows farrow at a target backfat level. "We don't know yet what the goal is, but we're trying to maintain 19 mm (0.75 inch) of backfat," adds Tokach. "We hope to avoid the precipitous drop to 13 to 14 mm (0.50 to 0.55 inch) that causes sows to leave the herd. Leaving the herd too early because of reproductive failure and mortality definitely needs work."

Current high replacement rates also compromise herd immunity from diseases that cause reproductive failure.

"Parvovirus doesn't keep us from getting 25 pigs per sow per year, but it's a significant cause of reproductive failure," contends Steve Sornsen, director of swine veterinary services for Pfizer Animal Health.

"High replacement rates make it a challenge to keep young-parity animals immune to reproductive diseases without vaccination," he notes.

Both parvovirus and erysipelas are issues facing today's breeding herd. Brett Bowers, a veterinarian with PIC USA, says parvovirus infections, characterized by increased returns to service and elevated numbers of mummified piglets, are still endemic in may units.

"The industry needs to be aware that there may be more 'negative' gilts out there than we ever thought," explains Sornsen. "Housing systems and closed herds have reduced circulating virus, which means there is more variation within herds. That justifies revaccination."

Timing of initial vaccination and boosters are critical-control points, since maternal antibodies may persist up to six months and interfere with development of active immunity, adds Sornsen. A comprehensive reproductive vaccine should be used four and two weeks prior to first breeding in gilts, as well as before each subsequent breeding.

Erysipelas risk also is on the rise, not only in the United States, but in other countries as well, says Laura Batista, a University of Minnesota swine veterinary researcher. Eliminating erysipelas vaccination may be a contributing factor.

"Vaccination is the only way to develop consistent immunity against parvo-virus, Leptospirosis and erysipelas," says Neil Shantz, a swine practitioner in Warman, Saskatchewan. He believes vaccination is a least-risk method to prevent reproductive failure.

The potential for increased productivity is huge, continues Sornsen, but producers need to shoot for lower gilt replacement rates. "Bringing in high numbers of replacement animals challenges acclimatization, and that's 90 percent of the battle in gilt development.

"At the end of the day, health is a significant factor in achieving higher productivity," he adds. "Parvovirus, lepto and erysipelas are major players that are easily stabilized with vaccination programs."

He acknowledges that proper nutrition and feed intake impact health as well.

"If gilts or sows are undernourished, they are more susceptible to disease. There's no doubt that some of the porcine reproductive and respiratory syndrome wrecks we've seen are in underconditioned sows," Sornsen says.

A Few Statistics
The latest USDA National Animal Health Monitoring System figures show that all herds surveyed averaged 10.9 pigs born per litter in the six-month period ending May 2000. The same herds averaged 10 pigs per litter born alive and 8.9 pigs weaned per litter. Herds with more than 500 sows averaged 11.1 pigs born per litter, with 0.9 stillborns or mummies.

Age was the most prevalent reason for culling sows (41.9 percent), while reproductive failure accounted for 21.3 percent and lameness accounted for 16 percent of the culls. Other reasons for culling included performance, upgrading genetics and poor body condition.