It is recommended that boars are kept well away from sows. The smell of sows has the potential to cause problems for the bond between boars, particularly when they are hormonal teenagers (approx 16 weeks to 14 months of age) . The reaction is stronger if sows are introduced into a boars only room - which we would not recommend to do. However, while boars who grow up around sows tend to be less affected by sow pheromones, it’s always best to err on the side of caution when it comes to teen boars as you don’t know how they are going to react.
If they must be in the same room, then stacking the cages, with the sows at the bottom and boars at the top is advisable. This is so that the sow smells cannot drift towards the boars. If stacking is not an option then ensuring there is an opaque divider between the cages which is higher and wider than the cage so, again, the sow smells cannot so easily drift. It is also essential that you do everything for and handle the boar pair first, again , so you don’t transfer sow smells onto the boars.
The cage sizes you quote is ok for the sows but a little too small for a boar pair.
Two sows need 150x60cm.
The recommended cage size for two boars is 180x60cm.
But any more space you can give them is always advisable, particularly for boars. If boars are kept in too small of a cage, then it can also cause them problems. Boars are more territorial and need more space.
While more boar pairs make it together than not, do be aware that at four weeks old they have not yet any ideas of dominance - at that age, they simply want to belong. When the hormones hit at closer to 16 weeks of age, there is the chance that even brothers will not be compatible. It’s always wise to have a plan b for living arrangements when it comes to taking on young boars, just in case the worst happens and they end up not being compatible once the teens hit. If that were to happen a d the boars have to be separated then given you already have two sows, you would have the option to neuter both boars and then split the sows up putting one sow with each boar.
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