National Hog Farmer is part of the divisionName Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Options For Parity Segregation

The evolution of swine production system design has been a rapid, dynamic process in the last 40 years. The progression from batch farrowing outdoors to continuous-flow, confined production to three-site production and finally, to multi-site production has led to significant improvements in productivity and cost reductions. Producers have come to recognize that even with multi-site production, there

The evolution of swine production system design has been a rapid, dynamic process in the last 40 years. The progression from batch farrowing outdoors to continuous-flow, confined production to three-site production and finally, to multi-site production has led to significant improvements in productivity and cost reductions.

Producers have come to recognize that even with multi-site production, there are still improvements that could be realized. They also recognize that gilts are a unique population of animals in the breeding herd that are often overlooked when it comes to meeting their special needs.

In addition, young breeding animals are often the source of disease for the entire production system. This fact has been reinforced to the swine industry with the emergence of the porcine reproductive and respiratory syndrome (PRRS) virus.

To address these challenges, a group of producers in Canada, led by swine veterinarian Camille Moore, began experimenting with the concept of maintaining gilts on separate farms and rearing the offspring separately.

Thus, parity segregation was born. Since that time, there have been a number of additional production systems in both Canada and the U.S. that have implemented parity segregation systems.

This article describes the authors' experiences working in and with these systems, and the potential benefits and real-world challenges of operating a parity segregation system.

Benefits of Parity Segregation Systems

Parity segregation has numerous benefits for both sow and growing pig production. As noted, gilts (also known as Parity 0 or P0 females) are the source of active disease transmission for the sow herd, creating active disease in both gilts and Parity 2 and greater (P2+) sows. The sow herd has lower mean performance and reduced predictability of weaned pig output over time due to both chronic disease and periodic epizootics from new disease introductions.

By separating out gilts, which tend to have higher rates of disease transmission than mature sows, the rate of infection in, and the risk of new disease introductions to, the majority of the sow population are reduced.

Gilts, by mechanisms that are not entirely understood, tend to clear most diseases during their first gestation. Multiple studies in Sweden, for example, have documented that Mycoplasmal pneumonia can be eliminated from sow herds by not introducing females under 14 months of age to the sow farm.

The production benefits of separating gilts are consistent and substantial. The biggest production benefit to gilt separation is the specialization of labor in breeding, feeding and caring for them. This specialization allows the customization of mating patterns and feeding practices from the first service through farrowing. If P1 females are retained for breeding on the gilt farm, then this specialization of labor can be continued though the P1 service.

As a practical matter, gilts on traditional farms are often overlooked for their special needs. The separation of the gilt farm makes implementation of gilt management practices easier, because there is only one location in a system to require implementation. In larger systems, staff can be dedicated full-time to these responsibilities, thus increasing the chance that the goals of the gilt management program are achieved.

Less expensive diets are an additional benefit. The gilt's daily amino acid requirements are higher than P2+ sows. Traditional mixed-parity farms feed diets that meet the gilt's needs. The feed costs can be reduced by feeding lower-cost (lower amino acid) diets to Parity 2+ gestating and lactating sows.

Furthermore, segregating the offspring of P2+ sows has shown substantial improvement in growing pig performance, primarily attributed to improved health. Moore, addressing the annual meeting of the American Association of Swine Veterinarians, reported on improvements in average daily gain, feed conversion ratio and a reduction in mortality in the offspring of P2+ pigs, compared to the offspring of mixed-parity sows (see opening article in this Blueprint, page 6).

And some have suggested that vaccinations against mycoplasma and many mass treatments can be eliminated in the P2+ offspring as a result of parity segregation. This allows interventions to be focused on the P1 offspring which represent 20-25% of the total pig flow.

However, there are no peer-reviewed, published data to support these anecdotal field reports. There are several controlled studies currently being conducted to confirm the many field experiences that indicate reduced need for vaccination and disease control measures in P2+ progeny.

Operating Parity Segregation Systems

The goal of a parity segregation system is to separate gilts, through the first farrowing, from P2+ sows. This separation is typically done by housing gilts and P2+ sows on separate sites in order to keep the gilts from transmitting disease to the P2+ sows. There is no agreement on how far the sites need to be separated to achieve the health benefits.

There are also several projects currently investigating whether the benefits of parity segregation can be achieved with the gilts and P2+ sows housed on the same site (similar to an on-site, off-site concept where the separation distance may consist of several hundred yards or more).

With parity segregation, the timing of the movement between farms varies between different systems. In some systems, the P1 sows are moved to the P2+ farms at weaning; others breed the weaned P1 sows at the gilt farm, then move them to the P2+ farm after confirming pregnancy (typically 40 to 60 days of gestation).

The gilt farm is sized to house all of the unmated gilts, breeding and gestating gilts and farrowing for all P1 sows. The total amount of breeding/gestation space required is determined by how long after weaning the P1 sows will be maintained in the gilt farm system.

The following are a few examples of different parity segregation system designs:

  • If the system is expecting an annualized 50% replacement rate, then the gilt farm will require about 25% of the total system capacity, assuming that P1 sows will be moved at weaning.

  • If P1 sows will be held until the middle of their second gestation, then the gilt farm will require between 30% and 35% of the total system capacity. The gilt farm would typically have isolation barns for incoming gilts. Many of the existing systems do not have an isolation barn for the P1 sows moving from the gilt farm to the P2+ farms.

However, in several systems, adding an isolation barn on the P2+ farm has reduced the risk of disease transmission from the gilt farm to the P2+ farm. This approach requires that sows be moved between farms on a periodic basis, instead of weekly, which does not fully utilize gestation space at the gilt farm. The approach does, however, lower the chance that disease would be moved between farms.

Should the gilt farm become infected with a new disease, the backup plan would be to move healthy, unmated gilts from gilt development into the P2+ farm to allow the depopulation or disease elimination from the gilt farm.

Also, the offspring from the gilt and P2+ farms would be moved to separate grow-out sites in separate trailers. These movements create two separate flows for growing pigs.

There have been several systems that have remodeled existing facilities to parity-segregated flows, and in these systems there is one gilt farm and several P2+ farms. The size of farms in these systems has been adapted to meet the existing facilities.

At least one new system has been constructed to allow for additional farrowing capacity at the gilt farm in order to increase lactation length at the gilt farm, relative to the P2+ farms. This accommodation was made to take advantage of the larger response in P1 females to increasing lactation length relative to P2+ females. This design allows for optimization of return on fixed assets across all parities.

One of the challenges with parity segregation is whether the concept is best suited to large systems. To investigate its value in smaller systems, there are several studies either planned or being conducted that are looking at the benefits of separating offspring by dam parity that were farrowed on the same farm.

In addition, there are unanswered questions about the separation necessary for the growing pigs in order to gain the benefits of parity segregation. The goal of these studies is to understand if the growing pig benefits of parity segregation can be achieved without the cost of separating the sow and growing pig facilities. This adaptation of parity segregation would allow all farms, regardless of size, to be able to achieve the benefits of parity segregation.


Parity segregation is a natural evolution of the pig flow strategies that the industry has employed. The placement of gilts on one site and P2+ sows on another location has proven to be a reliable way to increase the stability of performance in sow farms and lower weaned pig cost.

In addition, there appears to be significant improvements in growing pig performance when pigs are separated from the gilt and P2+ sow farms.

In the next year, as more systems adopt parity segregation and research is published, the best methods to implement parity segregation and the potential benefits of this production method will be further elucidated.