Sow parity management is always worth scrutinizing, as costs and returns associated with sow attrition rates certainly affect your bottom line. 

Challenges start early, as first-litter gilts often do not consume enough feed and thus pull from body reserves to support piglet growth. This can result in gilt litters that are lighter-weight and lower in number when compared to older sows. Consequently, productivity per sow can generally be increased by reducing the percentage of gilt farrowings.

Parity-1 and parity-2 sows also may be more susceptible to increased weaning-to-estrus intervals and lower farrowing rates and litter size compared to parity-3 or older sows. Parity-specific insemination schedules may be beneficial, given parity-1 sows’ longer weaning-to-estrus interval and shorter estrus duration.

Reproductive performance through the first few parities can be improved by removing sub-fertile females from the breeding herd. On the other end of the scale, sow productivity can decline beyond the sixth or seventh litter. However, nutrition and management often can extend sow productivity by two to three parities.

Attaining the optimal parity distribution within a herd is a complex task. It involves analyzing replacement-gilt costs, feed-ration prices, litter size and performance, conception rates and weaned-pig values, according to Kevin Dhuyvetter, Kansas State University agricultural economist.

Dhuyvetter estimated budgets based on culling sows from parity-1 through parity-10 to determine if an optimal culling strategy exists. His results showed that a breeding herd comprised of 18 percent to 20 percent gilts and a herd parity average of 3.5 to 4 provided optimal return.

To achieve a parity distribution of less than 20 percent gilts, the study found that sows needed to remain for at least eight parities. Dhuyvetter also found that weaned-pig costs decline at a decreasing rate as sows remained in the herd for additional parities.

Fluctuating sow, gilt and feed prices will make the optimal sow parity a moving target, which prompted Glynn Tonsor, fellow Kansas State agricultural economist, to update Dhuyvetter’s work. (You can access the study at

Tonsor found when replacement gilts are valued at 25 percent less than the assumed value, returns over total costs increase by $1.77 per head and are maximized after eight parities. When replacement gilts cost 25 percent more than the $225-per-head base, returns over total costs are further reduced by $1.70, but the optimal cull time is parity-9.

His update reveals that the most economical time to cull a sow is after her eighth or ninth parity. He also found only small differences in returns for any strategy keeping sows between six and 10 parities.

Tonsor discovered that feed-ration prices, conception rates and weaned-pig values have relatively little impact on optimal culling strategies. He also found that the increase in returns associated with improved conception rates is notably less than the drop in returns accompanying a setback in rates, illustrating the need to monitor actual conception rates.

Many factors can affect a sow’s longevity, notes Ken Stalder, Iowa State University swine geneticist, including gilt development, nutrition, body condition, housing, feet and leg soundness, season and management, among others. “This can make solving sow longevity challenges a long and difficult process,” he adds. “If a pork producer is experiencing challenges with sows having long, productive herd lives, then focusing on one or more of these factors should help improve longevity.”

Identifying optimal sow culling is an important component of a sound management plan. Keeping a watchful eye on the factors listed here can help determine the optimal parity distribution for your herd.

Dam Parity Affects Offspring Growth Performance

The effect of dam parity on piglet growth performance was studied and reported by Tom Burkey, swine nutritionist, and Erin Carney, graduate research assistant, both of the University of Nebraska. According to their report, progeny from parity-1 sows have lower weaning weights, decreased average daily gain in the nursery and finisher, and higher mortality when compared with progeny from parity-2 or older sows.

Their research compared the growth performance in the nursery for 96 offspring from parity-1 and parity-4 sows, with initial bodyweight averaging 12.56 pounds and 13.98 pounds, respectively.

Piglets from each parity received a control diet or a control diet plus carbadox at 50 pounds per ton of feed. Pigs were housed in a temperature-controlled room and all diets were fed in meal form.

The study found that the bodyweight of parity-4 progeny exceeded parity-1 progeny on days 0, 7, 21 and 42, when averaged among dietary treatment groups. Overall, parity-4 progeny tended to have greater average daily gain and average daily feed intake when compared to progeny from parity-1 gilts. The differences on day 0 did not affect performance on day 7, 21 or 42. Also, on day 42, pigs fed the control diet tended to have greater bodyweight than did the pigs fed the control diet plus carbadox.