The major question that arises in the group housing planning process relates to pen design and sow grouping strategy. Should I design around static or dynamic sow pens? And should I house the sows in large or small groups?
The research is in and it shows you should go with...well either really. In practice and in research facilities, both static and dynamic pens will produce at a high level with skilled management. According to a review of research by the Prairie Swine Centre, there are no significant differences in birth rate, still births, lameness, or any other major production measurements among sows in static groups and dynamic groups.
While either pen strategy could work for you, it is important to know the advantages and disadvantages of both.
The majority of static pens are not nearly as large as dynamic pens, which can be both a positive and negative. The size of static groups depends on your overall herd size and the number of sows bred at once, as well as the type of feeding system you implement. Because they tend to be smaller, static pens may seem like they do not require as much management and oversight but that overlooks the vital task of sizeing and combining animals well when filling a pen, especially in a competitive feeding pen.
Static pens also tend to be filled (and emptied) quickly with greater numbers of animals being introduced at once where dynamic pens allow trickle filling of 10-15 animals at a time. Filling pens all at once tends to produce more aggression in sows early on, but once the girls settle into their social hierarchy, they tend to calm down and the social structure remains intact for their entire time in the pen.
In practical experience, we have seen that sometimes farms opt for static pens because they are wary of new technology and the idea of training their staff on a new system. We find that some farms continue with static groups even when they would prefer to move to dynamic because they lack faith in themselves to effectively manage a dynamic barn.
Dynamic pens offer more flexibility in a barn as you can use available space in any pen if needed. While static pens cannot have animals added to the group if there is extra space created by pregnancy loss, dynamic groups can add extra animals quite easily. Dynamic pens also make the most efficient use of space since less room is wasted on alleys.
Typically dynamic pens require a higher level of stockmanship as these pens tend to be larger and barn staff must be able to identify needs, health issues and body scoring within a greater number of animals. With that said, small static pens (with competitive feeding) may also require a very high level of stockmanship (selecting groups based on size and condition, checking sows daily for drop-outs at feeding time, higher drop-out levels requiring removal and specialized care etc.)
Just like with static and dynamic grouping, both large and small pens can work with the proper design. That being said, it has been clear that large pens make better use of the barn and tend to produce less aggression in sows. Dr. Jennifer Brown with the Prairie Swine Center, who is working with the National Sow Housing Conversion Project had this to say about pig behavior in small and large pens:
"Studies on finisher pigs show that in large dynamic groups, pigs adopt a more tolerant social behavior. When they are in small groups, they have a more defined social hierarchy, and show a greater response when mixed with unfamiliar pigs. Think of living in a big city vs a small town. When someone new enters the city, you are more passive towards them - you don't notice and don't care because you are used to all the people, and you can't dominate the entire city. In small town, you know everybody, and it's a disruption when new people enter. You try to figure them out and where they fit in your community. It's easier to be the boss of the small town than the big city. "
While the main questions people ask are whether they should implement small or large pens and whether to go with static or dynamic pens, you have to dig deeper. You should also consider grouping factors that affect sow performance and ease of pen management.
When considering your grouping strategy, you can group all parity levels together -or- you can separate your sows by parity. Separating by parity maximizes your space allocation in the barn.
Group 1: P1-P2
Group 2: P3-P4
Group 3: P5 & up
There are a number of producers who have found that even in dynamic groups there are better interactions when P1 and P2 animals are penned separately from older girls. Such separation is more difficult in smaller barns, but in larger herds (>1000 sows) it isn’t uncommon to find three separate groupings. Dynamic grouping by parity can be done in herds with as few as 500 sows, but at that size they can only divide into two groups effectively.
Grouping sows by parity also plays a role in pen performance. Dr. Brown had this to say about grouping sows by parity:
"Parity grouping of sows is critical for the success of competitive systems, but it is also useful in non-competitive systems. We did a large study on this question at Carthage Veterinary Services (5000 head sow barn in Illinois). We formed separate groups of low, medium and high parity sows (no gilts), and compared their performance against that in mixed parity pens. The main difference we observed was that low parity sows had significantly better backfat levels when they were grouped separately. In this study, we were also a bit surprised to see that the younger animals performed more aggression."
Grouping by parity is not the difference between success and failure in a barn, but it is becoming clear that there are many performance and cost benefits when low parity and high parity sows are grouped separately. While this is not impossible in small groups, it is much easier and more cost effective in large groups in a large barn.
So, Which Combination is Right For Me?
There are plenty of salesmen out there that are going to tell you that only small static groups or only large dynamic groups will work. But the truth is you need to figure out what will work best for you and your staff.
From our experience, if you are building a new barn, we recommend building your sow pens for large dynamic groups that are separated by parity. Again the sows are more tolerant and less aggressive. In addition, your pens are already built with the necessary space for subordinate sows to escape from more aggressive sows.
In smaller pens, you will waste square footage in order to make the pen large enough to accommodate for this. Small pens also tend to bring the entrance and exit of the feed stations too close together. As we mentioned, small static groups can be successful with a highly skilled barn staff, but they won't be as cost-effective and they will be harder to manage well.