Components Of Parity Segregation

Components Of Parity Segregation

Byline: Camille Moore, DVM Swine Consultant, Quebec, Canada

The evolution of the swine industry over the past 20 years has been quite phenomenal. Techniques like segregated early weaning (SEW) and three-site production were not in existence at all 20 years ago, yet they are probably the gold standard of pork production today in North America.

In the beginning, the dream of SEW was disease elimination. But in reality this technique is much more of a disease control technique than a disease elimination technique. The improvement in productivity was probably related to the true application of the all-in, all-out (AIAO) principle, and also the specialization of both staff and site.

Parity segregation aims to take those AIAO and specialization principles one step further to enhance the productivity of the overall system.

Defining Parity Segregation

There are basically two components to parity segregation: sow herd and progeny/offspring.

At the sow herd level, parity segregation is the segregation of gilts and first-parity (P1) sows from the older, second-parity and above (P2+) sows. The segregation of P1 sows can be done any time after a sow weans her first litter, and before she farrows her next and becomes a P2 sow.

For the progeny of the sow, the goal is to achieve complete segregation between the offspring of the P1 sows and the offspring of all the other parity sows.

As with SEW and multi-site production systems, many options could exist within this general definition based on production goals, production status and problems to be solved.

In consequence, during the implementation of parity segregation, animals could be moved at different times of their cycle and many different scenarios would exist.

Figure 1 summarizes the five main components of parity segregation. Within those five main production points, other subcomponents could be added based on needs. Keep in mind that there may be advantages from using only a part of the total parity segregation system.

In the first system where we developed parity segregation, the steps outlined below were followed:


Early gilt exposure to the pathogens in the production system;


Segregation of gilts during the rearing process;


Gilt breeding and gestation;


Farrowing of P1 sows and rebreeding;


Introduction of P1 pregnant sows as replacement animals in the “old sows” breeding herd; and


Complete flow segregation of the P1 and P2-plus offspring.

Why Parity Segregation?

The original driving force for the establishment of parity segregation was in response to all of the problems related to gilt development, introduction, gestation and farrowing.

Based on the lessons learned from three-site technology, it was thought that this concept of segregation could be pushed one step further to enhance gilt development.

Advantages and reasons for parity segregation can be divided into three groups:


Focus on gilts – Parity segregation will allow pork producers to raise gilts properly – providing them with the right feeding program, the right building and the right amount of space to grow properly.

After gilts have been grown out, it’s crucial to focus on their final development. Parity segregation will ease the implementation of programs that support proper backfat deposition on gilts and provide adequate boar exposure. These are critical to final reproductive development of gilts.

Regrouping gilts in one building with dedicated staff will allow for better estrous detection and make specific matings easier.

When all gilts are farrowed in the same barn, a specific lactation diet can be fed to take into account the normal lower feed intake during the first lactation.

And, it’s a well-known fact that first-parity sows act completely different at weaning than older sows do. Regrouping the P1 sows will make usage of specific programs and mating patterns easier.


Health advantages – Gilts can often be a destabilizing factor when they are introduced into a herd. In a designated gilt grower barn, having animals of the same age with a prolonged acclimatization period greatly helps to reduce the risk of destabilization in mature sow herds when P1 gestating sows are introduced. Gilt introduction normally acts as a destabilizing factor on most farms.

With parity segregation, herd health is stabilized, even in older sow herds dealing with porcine reproductive and respiratory syndrome (PRRS) virus.

Health problems related to gilts and their progeny at first farrowing are common. Undoubtedly, gilts and their progeny carry a lower immune status. Therefore, gilts are generally more susceptible to diseases like mastitis-metritis-agalactia (MMA), and their piglets are more prone to scouring.

Regrouping all gilt farrowings in one location makes the implementation of disease-specific prevention programs much easier.

However, using parity segregation to control Mycoplasmal pneumonia in progeny from first-parity females has struggled. The problem seems to disappear in progeny from P2 and older sows without the aid of vaccination.

For example, in one system looking at slaughter check lesions for enzootic pneumonia, a three-fold reduction was seen in the severity of lesions in the progeny of P2 sows vs. P1 sows. In that system, no vaccinations medications were used on the P2 progeny, and both were provided to the P1 progeny.


Management advantages – Another advantage to regrouping all gilts on a given farm allows for the development and use of more specific equipment.

For example, producers could use narrower and shorter gestation crates, as well as narrower farrowing crates. Because we know we will have to deal with prolonged wean-to-first-service intervals in P1 females, more space can be provided in the breeding square, or hormonal therapy may be applied more aggressively.

Weaning weights of gilt progeny are normally lighter than those of older sows. This is probably due to lighter birth weights and to lower feed intake. Lower weights at weaning will usually result in lower weight gains in nurseries and finishers.

Keeping P1 litters together allows producers to design a system that builds in the extra space needed to reach optimum market weights while reducing variation within a barn.

Parity segregation can also help achieve consistent throughput. Designing a production system that allows gilt production to be segregated and maximized provides for a consistent supply of quality gilts into the breeding herd, enabling weekly farrowing targets to be met week after week.

Better Pigs Through Progeny Segregation

Assessing the advantages of the offspring in a parity segregation system is not always easy. We have already mentioned some of the health advantages related to PRRS and mycoplasma control. Table 1 describes the differences in production seen between the P1 offspring and the P2 offspring in a given system over a two-year period. In this case, the advantages of the P2 offspring over their P1 counterparts add up to a $2.50 advantage.

Specifically, offspring segregation has:


Allowed us to stabilize PRRS in the progeny. Today most nursery batches from the mature sow herd are negative for PRRS at the end of the nursery phase.


Helped us to stabilize PRRS in the mature sow herds we oversee, where there hasn’t been a PRRS break in the past three years.


Improved control of mycoplasma. Vaccine is no longer used on the progeny of the P2-plus sow herd, while a strong vaccination program is still needed on the P1 progeny. As described earlier, lesions due to enzootic pneumonia have been reduced three-fold for the P2 progeny at slaughter.

Table 1. Production Results for Parity 1 and Parity 2+ Progeny

As a caution, the figures for the two progeny groups in Table 1 were obtained from side-by-side comparisons, and do not provide a good basis for results obtained prior to the split of the two groups. However, a retrospective analysis of the records of that enterprise indicates that the results obtained today with P1 offspring are similar to those obtained when the two progeny groups were raised together.

Transportation costs of offspring segregation are not included in the cost structure.

All in all, there still appears to be a real cost of production advantage to using parity segregation on the offspring of P1 and P2-plus sows.

Gilt Acclimatization and Development

One of the main goals of parity segregation is to focus on the gilt. Even with parity segregation, producers must pay close attention to acclimatization and development of gilts. This process has three main components – an exposure phase, a cooling-off phase and a final development phase.

Exposure phase – In the vast majority of the industry today, replacement gilts are healthier than the receiving herd. Therefore, gilts must be exposed to the pathogens of the receiving herd. This exposure needs to be done as early as possible to make sure the potential setback caused by the pathogens will not interfere with sexual development and subsequent reproductive performance of the gilts. With PRRS, for example, we know that the development of immunity might take longer, so the exposure should occur as early as possible.

This exposure can be accomplished by direct animal contact, by exposure to animal tissue or by the injection of infected serum. Usage of commercial vaccination or medication programs could also help in gilt development and immunity.

For direct animal contact, our recommendation is to raise replacement females in a continuous-flow (batch system) nursery. For each nursery pen of 10 to 20 gilts, place one growing pig derived from the progeny of P1 females. Belief is that the P1 progeny carry a more representative sampling of pathogens in the system. The replacement animals should be kept up to 70 days of age in the nursery exposure phase.

Cooling-off phase – After animals have been exposed to a specific pathogen, they could shed that organism for a period of time. To avoid re-infection of the existing herd, it is very important that any replacement gilts introduced to a herd are not shedding.

This makes the cooling phase after exposure very important. Depending on the targeted disease, this cooling-off phase could be up to 120 days.

The cooling-off or quarantine phase provides an opportunity to finish the gilt development process. A proper feeding program should maximize protein deposition up to 135-140 days of age, then maximize backfat deposition.

For this phase, we place gilts in a small, isolated finishing barn from 70 days to 150 days of age, maintaining group integrity and providing 10 sq. ft./gilt of space.

Final development phase – After 150 days of age, the gilt enters the final development phase. Between 150 and 190 days of age, the diet should maximize backfat deposition. During this period, direct boar contact is advised. Animals should be kept isolated during this phase as well. The goal is to breed the gilt at her second detected estrus, when she should weigh 297-308 lb. with a backfat of 16 to 18 mm (.64 to .72 in.) and be 200 days of age or older.


We are still in the infancy of understanding all the pros and cons regarding parity segregation.

However, the results obtained so far make this breeding/reproduction strategy attractive, and we expect to learn much more about its benefits within the next few years.

Risks Related to Parity Segregation

We have mentioned many advantages related to parity segregation, but as with any strategy, there are also risks and pitfalls related to the application.

First, parity segregation reduces the flexibility in a system. After the implementation of parity segregation and the use of P1 females as replacement animals for the older sow herd unit, the system becomes much more of a continuous-flow system and animals need to be moved on a regular basis. This reduces flexibility, mainly in the face of a disease outbreak.

The other danger of parity segregation is related to the biosecurity risk posed by making the use of isolation units at each sow farm much more difficult to implement. However, if off-site gilt acclimatization is done well and the cooling-off phase properly set, this phase could easily become the isolation period for each group of animals.

Parity segregation in a system under expansion is more difficult to apply. When establishing a new herd, due to the fact that replacements will be brought in as P1s, we need to plan replacement matings at the same time that we are doing matings for herd establishment. This will increase the number of gilts needed and the space needed for the production of those animals.

Exposure to pathogens is also critical. Our goal is to expose animals to herd pathogens early to enhance herd health stabilization. If for some reason proper pathogen exposure does not occur, there is the possibility of introducing naive animals and placing the receiving herd at risk of infection.

Parity segregation increases the number of movements for animals, adding to transportation costs and increasing the risk of contamination.

Location also needs to be taken into consideration. The scientific community does not agree on proper separation distances between gilts, P1s and their offspring and the rest of the system. We recommend a minimum separation of two miles. Each pyramid should also have a dedicated transportation fleet.

With replacements being produced in a common location, a disease break at the site could potentially transfer problems to every production location.

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