I've seen a lot of different opinions on when it's actually safe to house a boar together with sows after his neuter surgery. I've seen 6 weeks, 4 weeks, 3 week or as long as 8 weeks.
In our case 3 weeks have passed since his surgery. Originally I planned to keep him separately for 6 weeks, but this poor guy has been alone for months and I really feel so sorry for him, and I can't wait to reunite him with the girls in a nice and big cage.
Would it be safe if I do it after 3 weeks?
The little baby in my avatar picture on the left (she passed away in August not long before her 8th birthday) is the unplanned daughter of a supposedly safe over 5 weeks post-op boar (not one of mine!) - just to make the point that it can really happen as late as that.
Because you are playing statistics, it can happen to anybody. All it takes is one still live sperm in the tubes...
Our forum recommendation, which follows UK welfare/good standard rescue practice (including RSPCA) is 6 weeks, which has borne out over thousands of boars being neutered in the intervening 8 years since Tegan's birth. There haven't been any more accidental births since her sudden arrival caused a huge stir in the UK piggy world. And believe me, any news of a post 6 weeks pregnancy would make the rounds like wildfire again!
When this forum was started, the usually recommended wait was 4 weeks but we have seen several cases of pregnancies resulting from this practice just on this forum in the early years to have had first-hand proof that the risk is still high enough to not bother cutting short the wait!
There is a very, very slim chance of a pregnancy after 6 weeks; more in the range of winning the national lottery. So far any rumours of post 6 weeks births have never been substantiated whereas I have got several more verifiable second-hand reports from people who personally knew somebody with an over 5 weeks baby like Tegan - but not a single one of an over 6 weeks birth.
I hope that this helps you to make a judgment about the risks involved? There is a huge difference between over half (at 2 weeks), over 90% (at 4 weeks) or 99.999% safe (at 6 weeks). You would have to wait for a full 3 months to be absolutely 100% safe - which is how long male sperm can survive at the very extreme.
As hard as it is to sit out a post-op wait (I have done it myself several times, so I fully understand your feelings!), it is simply not worth risking it too early when your boy is perhaps two thirds safe.
Your boy may be happy but instead you are putting your sows' and any potential babies'
lives at risk, not just their happiness!
The risk of fatalities in babies and/or mother during birth is as high as 20% - that means that even with the best care, every 5th birth ends with a death because pups are much larger when born compared to human babies; with less than optimal care and older sows, the risk rises quickly.
You are welcome to have a look in our pregnancy section to see just how peppered with deaths it is! All I can say is that dealing with the loss of any piggy is tough and comes with feelings of guilt as part of the normal grieving process, but knowing that you have caused unnecessary and entirely avoidable death is not easy to live with at all.
What you CAN do, is to place your boy in a safe cage he cannot get out of right next to your sows so they can interact through the bars and get to know each other over the coming weeks. This will enhance the chances of acceptance and give your boy the company and stimulation that he craves in a safe way; any cage gnawing will die down within a few days when he realises that it won't get him anywhere.
But please be aware that boars can be amazingly determined and athletic when it comes to climbing, jumping or wiggling through obsctacles when a sow is in season - and that is exactly the time you don't want them to! A traditional cage would be best for the purpose - you should be able to find some cheap second-hand ones on your local free-ads to use as an emergency or hospital/quarantine cage or sell on again afterwards.
This guide here contains a video link in the chapter 'What do boars need':
A Comprehensive Guide to Guinea Pig Boars
