Early group sow housing pens were known for high levels of aggression among gestating sows. This has been a counter argument on group gestation pens for years, but the amount of sow aggression depends completely on your pen design. To mitigate aggression, we must first know why the animals are aggressive, and then we can understand how to design a hog pen that reduces harmful behavior as much as possible. Hog pen designs have advanced since the early layouts in the 1980s, but there are still, and most likely will always be, aggressive sows in your herd. That is why it is vital to put your pens together with these four guidelines in mind.
1. Give the Girls Some Space!
There are generally two main reasons for aggression in group sow housing: group formation and feeding-related. Group formation aggression occurs as the pigs sort out their pecking order within the pen. Pigs tend to form social groups, or subgroups, of around 5-10 animals. As new sows are introduced to the pen and are entering social groups, the more dominant sows (typically the older and larger girls) will show aggression towards the new entries to establish their position in the group. When the dominant sow feels threatened, she will fight the other pig off, and she won't settle until the other sow is a good distance from her, typically around 30 feet away. This is a key reason we give the girls some space to establish their group order and to allow for healthy separation between disagreeing girls.
As a rule, we design group gestation pens with 24 square feet per grown sow or 20.5 square feet per gilt. This number will be marginally higher for each pen in a straw barn. This allows for plenty of room in each pen for the subordinate pigs to reach a distance the dominant animals are comfortable with. At the same time, the pen will not be so large that you are wasting unnecessary space in your barn.
2. Separate Your Sows by Parity and Size
Immature gilts and older sows are vastly different animals. Although their genetic makeup is identical, there are issues with size, hormonal differences, maturity and experience. Gilts have not learned to use ESF stations as efficiently so they will need more time during eating, which should translate to less girls per feed station. Gilts require less space as their bodies are significantly smaller. They are additionally not as experienced at participating in a large gestation group. Couple the inexperience with changing hormonal levels during their first pregnancy, and gilts are better put in a pen with others like them.
Sows on the other hand need more space due to larger bodies. These pigs will also interact better with each other. They’ll join a pen more readily and be much more efficient at ESF station use.
Every ESF barn design should have separate gilt and sow areas to function as well as possible.
3. Design the Group Gestation Pen For 100 or More
We recommend designing each pen for 100 pigs or more for a couple reasons. First, by adding that many sows, you are expanding the total square footage of your pen. We have found that these larger pens tend to be calmer than smaller pens because there is more total space for the girls to move around. When one sow shows dominant behavior, the other sow has more than enough room to move away in larger pens.
The second reason is that the pigs are more tolerant of others in larger pens. They are used to new pigs frequently entering the group gestation pen, so they are less threatened by strangers. Also, as the girls grow older, they are involved in more and more social groups. They become comfortable with group formation and accepting strangers into their groups. We always encourage the promotion of good habits in swine barns, and putting together hog pen designs for 100 animals or more will help foster these good habits.
4. Properly Design Your Feeding Systems
Knowing how to build a hog pen properly depends on how well we understand feeding-related aggression and how to eliminate the forces that cause feeding-related aggression. It's no secret that animals become territorial over food. Since there is no way to completely train this out of their behavior, we must take away the opportunity for dominant sows to show aggression and therefore the opportunity for any girl to feel threatened. While other systems may be used to achieve this, Electronic Sow Feeding (ESF) systems are the best and most complete solution. With ESF systems, all the pigs will be able to eat individually without any external threats. They are also designed in a way that does not allow the dominant sow to have control over others during feeding times. Learn more on how ESF stations operate and reduce the amount of stress in among your pigs.