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Neutered / De-sexed Boars And Neutering Operations: Myths And Facts

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Staff member
Mar 10, 2009
Coventry UK

Many people with fighting teenage boars are still advised to neuter their boars by general vets that are not familiar with the big difference between rabbit and guinea pig social behaviours.
Neutered boars are also much touted as peace-makers in sow groups; this has unfortunately got its limits as I know from my own rich experience in this respect!
The first part of this guide is looking at all the myths still surrounding neutered boars and in which scenarios and for which purposes neutering and neutered boars actually make sense.

In a second part, this guide is looking at neutering operations, again trying to sort myths from fact considering that most online information available is in no way representative. There are unfortunately plenty of horror stories around, but hardly any accounts of the vast majority of successful operations that go without a hitch and that usually go unreported for exactly that reason!
This part looks at how you can minimise operation risks, the range of cost to expect, neutering ages, how you can prepare and what to look out for during recovery as well as the important post-op safety wait.

Thirdly, I am going to demonstrate by the example of my own teenage boar Nye in 2017 how a problem-free neutering operation should look like and to which extent it has influenced his behaviour post-op. This part contains pictures of the recovery process as well as a couple of short videos from immediately after the operation and from his teenage behaviour a bit later on.

Part I: Neutered boars

Myths and facts

Myth: Neutering fighting boars will calm them down and enable them to live together happily
Fact: Neutering does most definitely NOT calm down boars in the short run and does NOT turn feuding boars into best friends!

It does in no way change their social behaviour, their personal chemistry or their personalities – two dominant boars will inevitably clash, whether they are brothers or unrelated, neutered or not!
Key to any successful boar bond is mutual liking and character compatibility – both factors that neutering cannot influence and that pet shops and for sale breeders fail to address.

If you struggle with your boars, you will find this very detailed guide here helpful. It is looking at the various phases of the teenage months and at bonds in crisis: what you can and can’t do to stabilise a bond and what options you have after a permanent fall-out, each with their individual pros and cons.
Boars: Teenage, Bullying, Fighting, Fall-outs And What Next?

Myth: Neutered boars can save a struggling sow bond or group.
Fact: A boar is not part of the sow hierarchy in a group. He acts as a natural outsider and he needs to be accepted by all sows. He can act as an integrator and as an absorber for seasonal sow grumpiness to a certain extent. That is so far correct.

However: A boar will NOT make your bickering sows become fast friends! Any divisions within a sow group or pair will remain. Your boar will take care to be on good terms with the lead sow and mostly associate with the sow he likes most or that decides that she is in love with him!
A ‘husboar’ will step into a dispute only if he is also the patriarch and like a first lady, there is only so much he can do if a friction turns into an open feud. More often than not, he will keep out of any sow-only feuds.
I have also had to eventually split several sows in those cases where a dominant ‘husboar’ had taken a dislike to them because they haven’t accepted him and submitted to him instantly; this grudge has been carried through over years and has eventually ended in open bullying at least twice.

Myth: Two neutered boars can live with one, two or more bonded sows
Fact: If you are one of the very few lucky ones with a huge cage and two very laid-back/submissive boars, an old age pensioners (5-6 years plus where the testosterone has run out) group or a disabled/carer piggy setting with different dynamics, you can count yourself lucky! The VAST majority of these kinds of foursomes will end in bad fights!

Unless you can provide the kind of really large habitat that takes up about half a room or even a whole room in a larger group, you are bound to fail.
You can either keep the sows in a pair (preferably well away and ideally on a lower level) to the the boars or bond each boar with a sow in separate pairs.
But there is no easy one cage solution for two boars and two sows!

Myth: neutered boars don’t smell
Fact: Neutered boars indeed don’t have quite as much full-on aroma compared to an unneutered boar and because of their shrunk anal sac, they are much less prone to collect as much gunk in there!

But they can still generate the most amazing cloud of testosterone if they get excited!
I prefer to do any boar introductions outside or in a room with open windows, as the testosterone laden pee with which excited boars spray the sows and anything around them can be on the overwhelming side!

Myth: Neutered boars don’t get impaction
Fact: About 10% of older boars develop mild or more severe impaction as the muscles at the back weaken. This happens irrespective of whether your boar is neutered or not.
But because the anal sac in a neutered boar has contracted again once his testicles have been removed, impaction cannot build up as badly as in a full boar.
For impaction care, please see this guide here: Impaction Recovery - How To Help Your Guinea Pig.


Staff member
Mar 10, 2009
Coventry UK
When is boar neutering useful?

Dealing with the results from an unplanned pregnancy
If you have suffered an unplanned pregnancy due to being sold a mis-sexed pair or an already pregnant sow, then you may want to consider having dad or a single male pup neutered so they can live with your sows again in the longer term. This goes for all odd numbers of boars you end up with as an alternative to finding a new boarmate for your leftover boar, especially if you do not want any more guinea pigs.

Until a reunion is possible and safe, a single boar CAN live next to sows with interaction through the bars (provided that he cannot climb over or wiggle through when they are in season) in order to keep their bond alive and make acceptance at a later re-introduction on neutral ground much easier.

Undescended testicles
If your boar has only got one descended testicle, it may be advisable to have him neutered in order to prevent problems long term. Please check with your vet.
Warning To Vet Check Irregular Boar Bits

If your boar or boars haven’t got any descended testicles by 6 months, please double-check their gender, first and foremost, before you see a vet in a panic!
We strongly recommend that you do this with every newly arrived guinea pig anyway and not just rely on the judgement of shop staff, previous owners, general vets or not necessarily experienced people playing the online picture guessing game!

Our sexing guide contains pictures of baby boars, boars with fully descended testicles and neutered boar bits as well as sow pictures. It also tells you how to safely check for secondary signs and not just rely on the arrangement of knob and slit, which can vary widely in both genders. Sexing Guide

Allowing fallen-out boars to live with a sow each
Boar neutering is also one of the options if you have got two fallen-out boars and want to bond them with a sow each. Cross gender bonds (provided that initial acceptance has happened) are the most stable of all constellations. Fall-outs are extremely rare!
It you want a pair that is going to stay together, then a sow - boar bond where one of them is de-sexed is by far the safest option!

How to make sow groups with a neutered boar work
I am very fond of my ‘husboars’ that have lived with 1-13 sows over the years. They do bring a positive element into a sow group because you are working with our guinea pigs’ social instincts and not against them.

The trick is to not use a neutered boar as a patch for existing problems, but to build up any group around either a dominant sow or patriarch from the start and to make sure that you do not upset the existing hierarchy with any further additions. Background checks (group background or submissive personality) and ideally dating at a good rescue are the best way of achieving this. It often pays adding younger sows in bonded pairs to small groups; this minimises outsider issues and allows group dynamics to develop. Acceptance is more often guaranteed.

If you want to extend your group from a couple of well-bonded sows to a trio, introducing a ‘husboar’ of their choice is a good option to prevent the frequent outsider issue that plagues trios.

Neutering as a safety measure
If you have both sows and boars in your household and small children or family members that are not bothered about keeping sexes strictly apart in your absence, then boar neutering is a way of preventing upsetting accidents!
Since my boars and sows time share the roaming area around my ground floor cages, all of my boars are neutered as a sensible precaution, irrespective whether they live with sows or not. It also gives me much more flexibility if one of a boar pair passes away.

Avoiding the headache of a bereaved older boar
If you do not live in an area with good access to rescues that offer boar dating with a rescue boar of any age but you have access to a good vet, then boar neutering at a younger age can make finding new company, especially similarly aged company of your boy’s liking (whether that is a sow or another boar), much easier.
The alternative is a live-alongside neighbour in an adjoining cage if you cannot date or afford a neutering operation.

Realising a boar’s dream
It is every boar’s dream to live with sows, and it is the most stable companionship. Unless you have witnessed the incredible joy of a neutered ‘husboar’ realising that there is a paradise on earth and that it is for real, you will not understand how much sow company means to a boar!
If you have the option of finding a solution for any single boar of yours, whether this is through bereavement or fall-outs that involves living with sows without the risk of pregnancies, then please consider this option!


Staff member
Mar 10, 2009
Coventry UK
Part II: Neutering operations

Finding the right vet

Key to any successful operation is finding either a general vet with plenty of experience in guinea pig neutering (generally for a rescue with a neutering policy) or an exotics vet with lots of practice in small furries operations.
This is essential in order to minimise the otherwise still real risk of deaths and post-op complications. If you haven't got access to a good vet, please only consider neutering if there is no other option available to you!

With more experience in small animal operations, fatalities have actually come down a lot and have become pretty rare, especially over the last five years. Problems with especially post-op abscesses are unfortunately still pretty common in our forum experience.

The best vets can however achieve as close to a 100% success rate in boar neutering as any surgeon can reasonably get, which includes the occurrance post-op complications. Finding a vet really makes all the difference!

Recommended UK vets: Guinea Pig Vet Locator
Recommended vets in some other countries: Guinea Lynx :: GL's Vet List

Operation costs

Cost of a neutering operation varies massively, especially from country to country.
In the UK, fees can range from as little as £40-50 at a no frills general vets chain to several hundred at a ‘super-vet’ clinic (in 2018).
In the US, Canada and Australia, a de-sexing operation is normally roughly in the range of $400-1000 (again, price range in 2018).

Please do your research carefully and take the time to ask around. A general vet who regularly neuters boars for a rescue is usually not a bad option if you have one in your area!
Exotics vets are generally more expensive, but you get a lot more service for your money in experience, operation techniques and expensive post-op monitoring and care, so you may want to take the level of care and services you are looking for into account.
There are admittedly some ‘super-vet’ clinics that clearly operate on the fact that their clients have insurance and that are working on making a profit, but many clinics aren’t – their operation cost is reflected by the high cost of medication and maintenance with salaries actually making only a small percentage of bill you pay.

You are always welcome to ask any vet clinic for their fees, experience in guinea pig neutering and their procedure before you commit to an operation.

Neutering age

When is a boar too old to be neutered?
Neutering operations are not any different from a normal operation in this respect. I know of several 4-5 year old boars that have been successfully neutered and even one 6 year old boar. My Carwyn was 3 years old when he was operated; he is now 6 years old and is still very much enjoying his life with his three younger ladies!
Recovery in older boars is a bit slower than in young ones, but that is the case with any operation as we age, irrespective of species. It is still only a matter of around two weeks in a straight forward operation recovery, though!

Compared to the sows I had to have spayed at those ages for medical reasons, boar neutering is a much less invasive operation; this is the reason why there are a lot more neutered boars around compared to sows.
Because spaying operations are much more invasive and often more expensive, there are only very few rescues that spay sows as a matter of policy; none of them in UK or in Australia unfortunately. These are the good standard rescues I know have spayed sows for adoption as a matter of policy if you are looking for company for a single/bereaved boar and do not fancy a neutering operation or getting a boarmate without the chance of dating before bringing him home.
- Portland Guinea Pig Rescue, Oregon US
- Piggles Rescue, Toronto/Southern Ontario, Canada
- Auckland Cavy Care, New Zealand

Neutering after the testicles have fully descended
Removal of descended testicles is the common method used in English speaking countries.
While boars can make babies from 3-5 weeks of age (and in exceptional cases even a little earlier!), their testicles only start descending around 4 months of age. This coincides often with large hormone spikes and the onset of the teenage months. This means that by the time your teenage boars are falling out, they are usually old enough for a neutering operation.

If you have any home born baby boars, this means unfortunately that they have to wait until they are old enough, plus the additional post-op safety wait.

Your vet will generally conduct a pre-op check to see how far the testicles have descended and to check whether your boy is fit and healthy for an operation.

Baby boar neutering (Early castration / ‘Frühkastration’)
Neutering baby boars before they become sexually active (i.e. around 2 weeks old/ca. 200g of weight) is virtually unknown in English speaking countries, but has been successfully practiced in especially German speaking areas for the last ca. 20-30 years.

The advantages of an early castration are that there is no need for a post-op wait; the baby boy can return straight away to his family and stay with it for the remainder of his life. At this young age, the rate of healing is very quick and complications are rare but not unknown.
Early castration eliminates the awkward separation between sexual maturity at 3 weeks old and the long wait until a neutered boar with descended testicles is safe to join his family again. There is also no risk at all that a baby will not be accepted back into their family.

This also means that keeping cross gender sibling pairs and family groups together is much more common on the European continent compared to the prevalence of same sex pairs in the English speaking world and especially the higher rate of fall-outs from teenage boars as a result of pet shops and breeders selling babies that are not character matched.

In fact, the pioneering Swiss system in which guinea pigs are not allowed to be sold, adopted or kept as singles also forbids the sale of any unneutered boars as pets in order to prevent uncontrolled breeding. As a result of this, shops and registered breeders often sell mixed gender baby sibling pairs.

Anyway, this comes at the price that while early castrates exhibit normal social interaction and rumblestrut and mount just the same as later castrates or full boars, they do not experience the hormonal development that teenage boars undergo. This lack of hormonal development is what many vets in English speaking countries that I have spoken about early castration have concerns about.

Long term experience in Europe has however shown that there are no major health problems or a shorter life span connected with an early castration.


Staff member
Mar 10, 2009
Coventry UK
The operation

Operation techniques vary and are still making enormous strides as more and more techniques from human medicine are finding their way into veterinary training.
The important part is not that the operating vet is necessarily fully up to date, but that he is familiar and comfortable with his preferred procedure and can keep the time under GA and the risk of complications/infections as low as possible.

This – graphic - guide here shows you pictures from a neutering operation if you wish to see what happens when your boy is on the operating table: Guinea pig castration explained

Post-op care and recovery

Ideally, your boy should come home after his neutering operation and behave and eat as if nothing whatsoever had happened. Thankfully the majority of operations goes well and without a hitch!

The following is the part that should be ideally NOT necessary!

If your boy is slow at coming round, in pain and is experiencing loss of appetite, please follow the tips in our post-op recovery guide. It is well worth reading it ahead of any operation, so you know what to look out for and what to do in case things don't run to plan.
Tips For Post-operative Care
Not Eating And The Importance Of Syringe Feeding

Make sure that you always have appropriate support care at home (recovery formula powder, probiotics etc.), just in case.
Your care at home can make all the difference in pulling your boy through, as it has in the case of my Hywel, who thankfully went on to have another 5 ½ years of the happiest of boar lives. With more antibiotics available now as well as more experience and better operation techniques, deaths during and in the wake of neutering operations are very rare with the right vet.

What to do when complications happen?

Please don’t spend valuable time asking online whether you need to see a vet, contact your vet asap if your boy is not right, experiencing lethargy (which is a life and death any time of the day emergency!), if any stapling/glue/sutures have come off and there is an open wound or if there are any swellings in the groin area or sudden loss of appetite.

Check the groin daily in the first two weeks, then every second day for the next two weeks. After a month, you can go back to a twice weekly check-up and after two months to the normal once weekly health check that we recommend for all guinea pig.
There can be a little bleeding in the first day as a reaction to GA drugs.

List of the most common post-op complications

Loss of appetite

- Immediately after the operation/on the day after the operation: Please step in with syringe feeding asap and follow the tips in the post-op and syringe feeding guides!
- Sudden loss of appetite typically in the second week after the operation: infection or abscess. Please see a vet promptly, ideally on the same or the next day.

Swellings in the groin area
- Haematoma (a ball of clotted blood in the tissue). This is harmless. See a vet as to whether they think it will dissolve on its own or is better removed.
- Abscesses are the most common neutering post-op complication. They typically appear in the second week after the operation, but can come up in rare cases as late as half a rear after the operation. Initially they can be felt as a hard ball, but as they blow up, they become softer.
Depending on how large the abscess is and where it sits, your vet may just treat with a strong antibiotic (ideally stronger than baytril, which is not all that good at cutting through an abscess), drain a larger abscess close to the surface or surgically remove a stubborn deep sitting abscess that is not reacting to even a stong antibiotic.
- Hernia (rare): Like with human men, the muscle wall in the groin is rather thin and prone to rips when under stress so fatty tissue or even a bit of gut can slip through – the latter is bad news but thankfully very rare.
Hernias are thankfully not very common, but they can happen in the operated area even a year after the operation. Unlike a an abscess or a haematoma, a hernia is a soft, squishy swelling to one side of the groin.
- Swelling at the back of groin that can cause gut adhesion: Thankfully extremely rare, but also extremely painful!
My Hywel (RIP 2016) survived it in 2011 thanks to determined round-the-clock care and a strong antibiotic. He is the only guinea pig I have so far come across with this particular complication in nearly 10 years on this forum.

The necessary 6 weeks post-op safety wait

Once the testicles are removed, there is still the contents of the tubes to be considered. As my own Tegan (whose dad is not one of my own neutered boars, just make that point clear!) is still living proof of, some remaining semen can stay viable for more than 5 weeks post-op! Tegan is not the only case I have heard of, even though a conception as late as that is pretty rare. But the law of statistics means that it can happen to anyone!

She is however a perfect example that there is crucial difference between 'mostly safe' and '100% safe' – and one that to my dismay even experienced vets can be rather cavalier about!
If you go to the trouble of putting your boar through an expensive elective surgery so he can live safely with a sow, the last thing you’d want is risk an unplanned pregnancy!
As endless as a full 6 weeks post-op wait can be, it is really not worth putting a sow’s life at risk through sheer carelessness!

Our forum recommendation follows best RSPCA (UK animal welfare league) and good standard UK rescue practice. With hundreds of boars successfully neutered and not a single report of any accidents since the extension of the duration, we can be sure that the 6 weeks post-op wait is really 100% safe!


Staff member
Mar 10, 2009
Coventry UK
Part III: A real life example

How a problem-free operation recovery looks like

I had my then around 6 months old Nye neutered at the beginning of January 2017. I didn’t mind travelling a bit further and paying a bit more (ca. £150) for an a routine operation in sterile conditions by a vet specialising with a long term 100% success record in guinea pig neutering.
Especially considering that my neutering experiences go back to the 80ies (the op was successful, but the GA was very harsh) and in view of my bad experience with Hywel's unusual post-op complications after a general vet operation of his short lived local rescue's choice in 2011. In fact, the clinic I had Nye neutered was the same that saved Hywel's life!

Nye before his op and after his op

1) With his full regalia still in place on the evening before the op
2) On the evening after his op (with the cavity left by the removed testicles packed with antibiotics)
IMG_3278_edited-1.jpg IMG_3295-1.JPG

3) 2 days post-op (with the operated area starting to swell down and contract
4) 2 weeks post-op (the anal sac is pretty much fully shrunk down)
IMG_3316.JPG IMG_3348_edited-1.jpg

This is a video of Nye in the evening after the operation after his return home.
As you can see, he is busy rumbling away, scent marking and flirting with the (spayed) sow next door!

6 months old Nye free roaming 10 days after the operation - no lessening of typical teenage boar behaviour!

Nye’s post-op teenage behaviour

In the weeks immediately following his neutering operation Nye was bursting with testosterone, like any typical 6 months old teenager whose testosterone output is at an all-time high. We did have a couple of times when he got a bit too much for his already neutered adult boar-mate Nosgan and needed a short term divider until the hormone spike had died down again after a couple of days.

Again, we went through a textbook phase between 8-10 months (i.e. 2-4 months after his neutering operation) when Nye was the archetypal annoying teenager, incessantly pushing Nosgan right to limit of his forbearance but generally not over it.

So no sign whatsoever of any calming down or any noticeable change in behaviour compared to a full boar!

Nosgan and Nye are a really well balanced and complementary pair of boars, which has carried them through the difficult times. They are still closely bonded and very much best of friends as adults, but they are not behaving any different to normal boars.


I hope that this guide helps you to make a more informed decision!

So far I have and have had 15 neutered boars all together with all of my previous 'husboars' living a normal life span between 5-7 years.
In truth, I wouldn't want to be without their boarly moments, when they are being told off by the girls, the boar hakas (territorial measuring up by rumblestrutting along the bars in sync) and their winding each other up through the bars - or the joy that their happiness of living with sows in a fulfilled boar life brings, especially the endearing boar habit of popcorning when they have been told off by a sow!
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