The impact of group housing on the reproductive and financial performance of any operation is based on numerous factors and their complex interactions. A space allotment that one producer may consider too small for sows works quite nicely for another producer when combined with a high-fiber diet causing sows to interrupt their eating cycles to drink more frequently, allowing timid sows more chances at the feeder.

An initial disaster when switching to group housing may improve after two or three parities due to indirect selection for docile replacement gilts. What one producer may swear by, another may fail with; ventilation, lighting, diet, breed, average parity, cull rate, stockmanship, post-implantation stall time, feeding system, age and upkeep of penning, stalls and concrete, depth of bedding, slope of floor -- all of these may interact to produce different results for different producers when moving to group housing of dry sows. Some collected research and anecdotal evidence from extant producers is presented below to assist in the thought process of designing and transitioning to group housing of dry sows.

Group size and status (dynamic versus static)


One of the first considerations for making the transition to group housing is the number of sows to place into one pen section. This will depend heavily on the feeding plan and farrowing program.


  • Large groups (more than 20 sows/group)
    • Advantages:
      • More cost efficient if using Electronic Sow Feeding (ESF)
      • Easier to introduce new sows/gilts into the group as timid sows can blend into the crowd and escape dominant sows
    • Disadvantages:
      • More difficult to give individual attention to sows/gilts
      • Unless farrowing in equally large batches, mixing and re-mixing of sows will be necessary, possibly increasing cull rate of sows from damage
  • Small groups (less than 20 sows/group)
    • Advantages:
      • Easier to work with static groups and small-batch farrowing
      • Individual attention and observation of sows easier
    • Disadvantages:
      • Harder to introduce new sows/gilts into the group
      • Not cost effective if ESF is desired
  • Static groups  of sows are initially assembled and then no further sows/gilts are added to the group until such time as the size of the group has dwindled through recycles and attrition that the group size is no longer viable, at which point the group is dissolved and a new group formed.
    • Advantages:
      • Once a hierarchy is established, significantly less agonistic behavior is noted among static groups than dynamic groups
      • If using a batch farrowing system, static batches work well with the all-in-all-out methodology for cleaning and disinfecting
    • Disadvantages:
      • Higher capital costs may be realized if pens are stocked to a certain density and not restocked following removal of recycles and cull sows. Extra pens are now required to maintain the overall number of sows needed in a static group system. Pens can be initially overstocked in anticipation of attrition but must be carefully monitored and managed during the overstocked phase
  • Dynamic groups  involve adding and removing sows from the group after initial formation. When the number of sows in a group changes there tends to be a period of aggression while the social order is re-established. This can range from one to four days, with the worst of the aggression usually occurring within the first four hours (this holds true in static groups, as well).
    • Advantages:
      • Allows maximum utilization of space by always maintaining stocking levels in pens
    • Disadvantages:
      • More frequent mixing creates more agonistic encounters as social orders are constantly being redefined

Feeding strategy


There are many ways to feed dry sows, which need to be considered in light of the size of the building and pens, as well as the personal preferences of the stockman, and with an eye towards costs. Some of the more common methods of feeding are discussed below.

  • Drop feeding.  This can be as simple as hand-feeding sows over the fencerow on a concrete slab or as complex as automatic volumetric drops timed to release a certain portion of food multiple times throughout the course of a day. The discussion following will focus more towards automatic drop feeding than hand feeding, although there are notable pig producers who prefer or even insist on hand-feeding to maintain the person-pig interaction. A variant of drop feeding is trickle-feeding, wherein feed is slowly released at a controlled rate rather than dropped instantly onto the feeding pad. This method serves to accomplish much the same result as dropping feed multiple times throughout the day, namely, to reduce aggression by giving sows the impression that feed is not a limited resource to fight over, that it exists in many locations and arrives multiple times.
    • Advantages:
      • Simple system to design and implement -- minimal electronics
      • Spatially and temporally separating feed drops within the pen reduces agonistic interactions resulting from a single point of feed.
      • Easy retrofit into an existing barn versus ESF
    • Disadvantages:
      • No individual feeding of sows based on Body Condition Score (BCS), although this can be overcome somewhat if sows are held in stalls for the first 28-35 days post breeding or groups are formed based on BCS feed requirements
  • Electronic Sow Feeding (ESF).  This system utilizes special penning arrangements to direct animals into and out of a protected feed area where an individual ration is fed to each sow identified by an electronic tag in her ear. Small portions are fed until the sow ceases to eat or reaches her daily allotment, at which point gates are opened and the next sow enters. Typical ESF stations can serve between 60-80 sows, which would be grouped together into a single pen.
    • Advantages:
      • Sows are fed individually, allowing feeding to BCS throughout the gestation period
      • Sows are completely protected while eating, allowing timid sows to eat their full allotment unmolested
      • Software prints out a daily report of feed intakes or skipped feedings per sow
    • Disadvantages:
      • ESF can be a labor-intensive system, relying as it does on complex mechanical and electrical systems that need protection from the environment and regular maintenance, along with tracking down animals skipping feedings or without RFID transponders in a large pen, and regular updates to the individual sow daily allowances.
      • ESF systems require substantial changes to pen design in retrofit scenarios, along with a higher cost than many drop feeding systems.