New systems of floor feeding and adding complexity to sow pens can reduce confrontations.
If sows can gain greater access to feed by being aggressive, encounters with penmates are inevitable. The aggression leads to a dominance hierarchy, which may affect penmates' access to feed.
To decrease the severity and frequency of these aggressive encounters, sows must perceive that feed is not a limited resource. This is best achieved with frequent meals spread over a large feeding area. Distributing feed widely throughout a complex or structured pen eliminates aggressive encounters by decreasing the perception that competing for feed will result in improved access.
Feed Delivery, Pen Design
Separate feeding areas within a single pen can be created by adding partition walls at the side or in the center of the pen (see photos). Adding complexity to a pen allows timid sows a chance to escape aggressive encounters and discourages aggressive sows from pursuing attacks.
A center dunging alley with solid eating-resting areas on each side is another way to structure a pen into distinct areas. With this configuration, timid sows can cross the slotted area to eat with a less aggressive group on the other side.
Partially slotted finishing pens are easily converted to gestation pens by simply removing the partitions over the slotted/dunging area between two or three pens, leaving the gates or walls over the solid area intact. This increases the total number of sows per pen and provides two or three feeding areas.
In groups of 20 or more, the sows' bodies also serve as “partitions” and create complexity within the pen, and the sows benefit from the increased “shared” space.
The “right” number of sows per pen is determined, in part, by the number of farrowings per week. Farms with less than 20 farrowings per week should consider batch farrowing so that a larger number of sows can be grouped.
Some producers choose to have a “dynamic” pen, where sows are constantly added and removed. Pen design, space allowance per sow and feeding methods are much more critical in these pens.
If some sows perceive that feed supply is limited, aggression will be continuous in a dynamic system, because new hierarchies are established whenever sows are added or removed.
Farms farrowing more than 40 sows a week should have two sow pens for each week so that sows can be divided by size or body condition. This makes it easier to control the amount of feed per sow — decreasing feed to the pen of larger sows and increasing feed to the pen of thin or smaller sows.
Floor Feeding Efficiency
Peak floor feeding efficiency is achieved by spreading out feed in both space and time. The use of cones or “Y” diverters on drop tubes can help dispense feed over a wider area.
The appropriate amount of feed for a pen of sows should be dropped in small amounts, 3-8 times throughout the day. Multiple feedings prevent sows from becoming overly hungry and anxious at feeding time, thus reducing the incentive to be aggressive. Automatic timers ensure regular drops without added labor.
Another method of providing multiple daily feedings is to split each feeding into two stages. With the first feed drop, the more aggressive sows start eating, leaving the more timid sows to move in and eat during the second feed drop.
These split feedings can be achieved by dropping feed in different areas of the pen at different times.
For example, in pens with a center dunging alley, feed is dropped on the solid floor at one end of the pen first, then 30-60 seconds later, feed is dropped on the solid portion at the other end of the pen. This allows the more aggressive sows to start eating as soon as the first feed drop occurs, leaving the more timid sows to move to the other end of the pen to eat.
When the sows are first mixed, they may move back and forth between the two feeding surfaces until each area has formed a stable group in which the sows are compatible.
Another alternative is to drop feed in the same area at two stages. Feed drops occur 15-20 minutes apart at each feeding episode. The more aggressive sows eat first and within about 20 minutes lie down to rest, while the more shy or slower-eating sows eat during the second drop. This is a good alternative where there is not enough solid floor space for all the sows to eat at once.
For drop feeding to work well, each sow should have at least 15 sq. ft. of feeding floor space. A 5% slope on the solid flooring surfaces running towards the slats ensures the solid flooring will remain clean and dry.
Practicality and Payback
Group gestation barns are a quiet, pleasant environment for sows and employees. They are often cheaper to build than traditional stall barns because there are no stalls, feed troughs or complex gutter and floor designs. Per-square-foot costs vary by region, however.
Naturally, the cost of a group gestation housing system also varies with design, square footage per sow, complexity of the pen, feeding method and amount of slotted area.
A recent review of building costs in Ontario showed that a group gestation barn with a pen structure, an automatic-multiple-drop feeding system and 25 sq. ft./sow costs about the same as a stalled barn.
Producers that feed group-housed sows several times a day report that sows are calmer than sows fed once a day.
However, even with perfect pen design and feeding techniques, an overly aggressive or shy sow will occasionally prove incompatible with the group. These sows must be relocated in a small pen for the duration of their gestation period.
Breeding Stalls Needed
Producers using the various group-housing designs commonly wean sows into breeding stalls to prevent them from injuring themselves or others as they demonstrate normal estrus behavior.
Time spent in breeding stalls varies. Some producers mix sows in pens immediately after breeding, while others keep the sows in stalls until they have been confirmed pregnant at about 35 days postbreeding.
If the gestation pens are well designed and managed, sows can be mixed immediately after breeding with little fear of aggressive encounters decreasing reproductive performance. Pregnancy testing in group housing is usually conducted during feeding time.
The various gestation housing designs and management systems discussed here were developed by Ontario pork producers through trial and error until they had limited or eliminated aggression between sows. The success of these systems has been evaluated in a number of ways:
The sows have fewer scratches, injuries and lameness, and their body condition remains consistent.
Farrowing rates are greater than 80%, with a few approaching 90%.
Producers rarely have to remove a sow that is not doing well in the group.
Some producers find that group sow housing barns are quieter and more pleasant to work in than stall gestation housing.
Questions regarding group housing or converting a conventional stall barn to group pens may be addressed to [email protected].