Sian Tranter MA VetMB CertAVP MRCVS
- October 10, 2020
A surprising question…….
Since the 1970’s vets have advocated neutering for prevention of cancer in dogs and cats. There is evidence for a reduction in breast cancer in neutered female dogs(1) and cats (2). Surgical neutering also eliminates the risk of testicular or ovarian cancer.
Sian Tranter MA VetMB CertAVP MRCVS
- October 7, 2020
When talking about neutering, vets often list a series of diseases that neutering can help prevent. Prostate disease is often near the top of that list - but is it true? What are the impacts of neutering on prostate disease in dogs? Our vet blogger Sian has been digging into the science in this, the first of our "Neutering Week" posts.
Dr Pete Wedderburn BVM&S CertVR MRCVSDr
- May 24, 2013
I knew I wasn't going to breed from my Hungarian Viszla so I made the decision to have him neutered which I did at six months old. Since then I have been told by the breeding fraternity that neutering at such an early age is a factor in dogs getting bone cancer. I cannot bear that I may have done something in good faith that could affect my beloved dog's future health. What is the truth?
This question from a VetHelpDirect reader is an increasingly common query from pet owners responding to internet rumours and discussions that are doing the rounds. As is often the case, the truth is complicated: we still do not know everything about the impact of spay/neutering, but we do know that there are pluses and minuses to having the operations done.
It does sound to me as in your case, with a Viszla, it was the correct decision. Early neutering is still strongly recommended for nearly all dogs as the best way to ensure that a dog is a good family pet. There are many behavioural advantages, such as stopping male dogs showing sexual behaviour, urine marking etc. And there are many health benefits too - reducing prostate disease, reducing certain types of cancer etc. And bone cancer is rare in Viszlas.
For female dogs, there are also many benefits from spaying. The operation eliminates the risk of unwanted pregnancy, dystocia and the physiological and behavioural changes associated with the six-monthly reproductive cycle. It eliminates the risk of pyometra, which occurs in 23% of intact females and kills approximately 1% of intact females. Mammary tumours are the most common malignant tumours in female dogs, and spaying before 2½ years of age greatly reduces the likelihood of this cancer.
Neutering and spaying has other beneficial effects on a society-wide basis: it prevents dogs from straying and dramatically reduces the problem of unwanted pups.
What about the negative aspects? A comprehensive review paper published in 2007 provides a detailed catalogue of the potential negative risks which seem to be more in some breeds and some cancers than others (e.g. more osteosarcoma in giant breeds like Newfoundlands and St Bernards). A more recent study on Golden Retrievers found an increased risk from other cancers and some joint diseases from early neutering but the study has been criticised by statisticians and other scientists as being potentially biased and not representative of the general population of dogs. It's likely that other studies are in the pipeline, so it's worth keeping an eye out for these in the coming years.
When reading these studies, it needs to be remembered that a big increase in the risk of a rare cancer may not be as significant to a pet as a small decrease in the risk of a common cancer. It is not easy for pet owners, unfamiliar with judging medical data, to assess these types of situations.
What should pet owners do? Refuse to spay/neuter their pet, then blame themselves when their male dog develops anal tumours or when mammary cancer affects their female dog? Or go ahead and spay/neuter, then beat themselves up when their pet develops osteosarcoma?
The best answer is that there is no perfect choice. The take home message is that you should not ignore the subject: all pet owners should discuss this with their vet. A decision should be made after addressing all of the issues above. Only in the fullness of time will you know whether it was the right or wrong choice.
The most important issue is that you carefully consider the various implications: at least then, regardless of the outcome, you will be able to look back and say " I did my best to do the right thing".
This is the time of year when people start to look at their cute little foals, and suddenly realise they're starting to grow up fast... As a result, it’s also when we start to get phone calls from people to talk about gelding them.
If you are considering getting a colt gelded ("cut"), my advice would be to contact your vet, who will be able to advise you on the best approach in your particlar circumstances. However, I'm going to try and go through some of the commoner questions below, so you've got some basic information on the decisions to be made, the procedure, and what you'll need to consider.
The first question, of course, is whether or not to get him cut. It’s an important decision, so these are my thoughts...
The majority of male horses are castrated, and for very good reason - very few people have the facilities, the time, or the inclination to manage an entire stallion. The old adage had it absolutely right - "You can tell a gelding, you can ask a mare, but you discuss the matter with a stallion". Although there are some superbly well mannered stallions out there, it takes years of expert training - and in my experience they're almost always more "bolshie" than a gelding, and much less forgiving of any mistakes. They are also much more easily distracted (e.g. by a passing mare), and prone to fighting.
Does this mean you can't train them well and keep them happily and healthily? No, of course not - but it’s a lot harder. The majority of stallions can't be kept in groups because of the husbandry regimes on most yards, so have to live on their own. That's not good for their mental health, or their owners and riders! If someone has the knowledge and facilities to bring up a stallion, I don't have a problem with that, and I wish them luck, but I've seen too many bored, frustrated and borderline dangerous stallions who haven't been brought up correctly, and remain a liability.
Geldings, however, can be kept in groups, can mix with other horses, and are less likely to lose the plot or throw a temper tantrum. They also don't present you with unexpected foals in your competing mares...
If you decide not to have him done, you need to be sure that you're doing it for the right reasons. The majority of horses are not necessarily good breeding material - you need to take an objective look at him and decide if breeding from him is actually going to benefit the breed. If you're avoiding doing it just because you don't like the thought of the procedure, you'll need to think long and hard about whether thats in his best interest - or yours.
If you are getting your colt cut, the next decision is when to do it. There are two major concerns - the time of year, and the maturity of the colt. In terms of time of year, it’s best to do it when the weather is cold enough to prevent flies from infecting surgical wounds. Ideally, then, this would be in late autumn or early spring, but gelding him in winter is perfectly acceptable if the facilities are suitable. Regarding the colt's maturity, there is an upper and a lower limit.
The lower limit is the most rigid - except in an emergency (e.g. a strangulating hernia), I would never geld a colt until both testes had descended into the scrotum - because it’s really important to make sure you've got both! This usually happens between 6 and 12 months old, but it is a bit variable. In addition, the colt has to be strong and mature enough to survive the surgery, although with modern anaesthetics this isn't as much of an issue as it used to be. The upper limit is much more flexible. Stallions into their twenties are castrated fairly commonly, but once they've passed through puberty, a lot of the stallionish behaviour is learnt, and won't be reversed by castration, including some forms of aggression, and mounting behaviour. Sometimes, people like to wait until a colt is 3 or 4 years old before gelding, but I think that often even that is too late - although it does allow the colt to develop more muscle, he'll also be developing stallion traits. In addition, the younger the colt, the smaller the testicles, and the smaller the testicles, the lower the risk of bleeding during the op. During puberty, the testicles increase dramatically in size, and as a result, their blood supply increases accordingly; the bigger spermatic artery in a post-pubescent colt is much harder to control bleeding from.
As a general rule (and it’s a VERY rough rule of thumb!) I'd normally look to geld between a year and eighteen months old. That said, there are a lot of exceptions - I once had to sort out the castration of a four month old colt because he'd started mounting his mother... There are also a number of opinions about weaning - before, after or at the same time? In this case, I think it depends entirely on the colt in question, and it’s an area (one of many) where I'll usually defer to the owner's judgement.
Before you go any further, its a good idea to get the colt thoroughly checked out - both testicles need to be present and easily palpable; if one is "shy" and difficult to find, I usually recommend checking again in a month or so. If it’s still inaccessible, the colt may be a cryptorchid (i.e. a rig, with one undescended testis). These colts should ALWAYS be castrated, and have to be done under general anaesthetic, if possible in a clinic. This is because the retained testicle, being kept at an abnormally high temperature inside the body, is more likely to become cancerous. Also, the defect may be genetic - and if so, he'll risk passing it on to his offspring.
Once you've decided when, there's another important decision you and your vet will have to make, and that's the details of the procedure. Basically, there are two factors to decide - firstly, do you want him done "at home or away"? Secondly (a related point), do you do him under standing sedation or down under a general anaesthetic?
Regarding the location, it depends on your practice's policy and facilities. Many practices now offer castration at the clinic, but the majority of people still choose to have the op done at home. The advantage of having it done at a clinic is that the procedure can be cleaner, and all the equipment and apparatus is there; in addition, many practices charge a callout fee for coming to the yard. However, that's offset by the fact that you'll have to transport the colt to the clinic; in addition, I think it’s usually less stressful for the procedure to be done at home, assuming the appropriate facilities are available. Exactly what facilities you need depend on the technique that's going to be used.
There's a lot of debate as to this decision, and some frankly ridiculous comments from some badly-informed people out there. I'm going to talk through the options and the pros and cons.
The two main options that you'll need to think about for the procedure itself are whether to have the op done under standing sedation or general anaesthetic. In some cases, the decision is easy - miniature horses and small shetlands should almost never be done standing, because they're too small for the surgeon to get good access and control the site, for example. Draft breeds are at a higher risk of eventration (see below, when abdominal contents escape through the castration wound), and so need a different surgical technique, which may be easier under a general; and fully adult stallions bleed more so may need better surgical access - again, a general anaesthetic makes this easier. However, most colts can be done either way, so you and the vet need to decide which you prefer.
Under standing sedation, the colt is given intravenous sedatives (see my blog on sedatives) so he becomes very dopey. He will continue standing up, but his head will drop, and he is likely to adopt a wide-based stance (which makes surgical access easier!). However, its important to remember that he is still to some extent aware of what's going on, so local anaesthetic is injected into the testicles (perhaps 20ml into each one, plus some under the skin of the scrotum) or into the spermatic cord (although I find that that's easier said than done, with most colts pulling the testicles up tight to the body wall so the cord is difficult to access from outside) to numb the area. The castration is then performed with the vet working from standing beside the horse. This approach avoids the risk of a general anaesthetic, and means the horse will recover from the sedative faster. However, the degree of sedation achieved is variable, and some colts appear to be more aware of the procedure than one would like, no matter how much sedative you pour into them. There's also a MUCH higher risk of the vet or their assistants being injured - unsurprisingly, some colts object violently if they realise what you're doing...
In addition, the surgical access is poorer (the vet is having to work upside down, and largely by feel) so if there is a complication, it is harder to control it.
Under a general anaesthetic approach, the colt is sedated and then given an injection of a general anaesthetic. He'll become very sleepy, and then lie down. Once he's out, an assistant lifts up the top leg, giving the surgeon access. The disadvantage is that most vets will only do a GA on a horse if there's another vet along to monitor the anaesthetic, which may affect the cost. In addition, a GA is a risk in its own right - one study suggested that the average mortality rate from GA in a horse is 1% (although this includes colics and emergency operations - the risk for a young, healthy colt is much lower). On the other hand, the risk of injury to the vet or assistants is much lower, and the risk of surgical complications is also much reduced, as the surgeon can see exactly what they're doing.
Is either one definitively better than the other? No. However, it is a decision to take WITH your vet, as they may have a preference that will affect their efficiency. For what its worth, I've done geldings both ways, and personally I prefer to do them under general, because its safer for me and everyone else around - and if there was to be a complication, I've got a better chance of finding and fixing it at the time.
The procedure itself is pretty much the same whichever way up the horse is. Along with sedation, I give an injection of an anti-inflammatory and painkiller, and antibiotic cover (no procedure done on a yard or in a field can ever be truly sterile, so I'd prefer to make sure there are antibiotics on board when we start). In the past, vets didn't routinely give painkillers as well as the sedation (which contains a painkilling component), but personally I don't think its fair not to.
There has historically been quite a mystique about the procedure itself - probably because people are a bit shy to discuss it. As a result, there is sometimes serious confusion - remember, gelding is NOT the same as a vasectomy, and it can't be reversed... Not even (as apparently happened to a colleague of mine) if the client stops you as you're about to drive off and, holding up a neatly severed pair of testicles, asks the vet to reattach them because she's changed her mind...
So, here's a quick run through the procedure:
The area of the groin is scrubbed with a skin disinfectant, and a final check is made that both testes are accessible. Whichever one is held closer to the body is the one I'll start with, just in case it is retracted later. I'll then scrub up so my hands are sterile. Some vets wear gloves, others don't - I don't think it really matters as long as they've scrubbed thoroughly. Gloves add an additional sterile barrier; but on the other hand they can reduce your feel and grip, so it depends on what the vet is happiest with.
Once the scrotal area is scrubbed, the vet will use a scalpel blade to cut through the skin of the scrotum. There are a couple of different options from here on, but the principle is the same; to cut down through the tissue to the vaginal tunic (the membranes that surround the testis itself) and then gently pull the testicle down and out. In an "open" castration, the tunic will be opened, in a "closed" technique, it gets left intact and the testicle pulled down still inside. Once there's enough slack in the spermatic cord (containing the blood vessels, nerves etc that supply the testicle), the emasculators are applied across the cord, with or without the tunic, depending on the technique. These are a clever bit of kit that crush the cord, preventing it from bleeding, while at the same time cutting off the testicle itself.
(Quick aside here - I was doing a gelding once and, as is customary, I showed the removed testicle to the owner to show it had been done; he was a teenage lad and he fainted dead away. Interesting ethical problem there - do I try and help the unconscious boy, or do I just keep working on the anaesthatised horse who'll soon wake up? Fortunately, he recovered on his own before I had to scrub out, but he was pretty green around the gills for the rest of the morning...)
In an older stallion, most vets will put a suture through the cord to ligate the artery, but this increases the risk of infection, so we don't always put one in if doing an Open procedure. After removing the emasculators, the vet will check closely for bleeding from the stump. If there isn't any, they'll repeat the procedure on the other side. If the surgery is taking place in the field, the vet will usually leave the incision open for drainage; closing it seriously increases the risk of post op swelling and infection.
As a note, there is always a bit of bleeding after the operation. The rule of thumb is, if you can count the drops, its fine! There's also invariably some swelling of the sheath, but again, it isn't usually anything to worry about. If in any doubt though, you should contact your vet. Your vet will give you instructions for post op care, but the most important thing is to keep the new gelding moving, to reduce the swelling and encourage drainage.
The complications to be aware of are bleeding, eventration, and infection.
bleeding is pretty obvious - some oozing from around the incision is normal, but there shouldn't be any significant haemorrhage from the stump of the spermatic cord. If there is, or if there's a lot of blood - call your vet! Uncontrolled bleeding is an emergency that may require a repeat surgery to control it.
eventration, is when abdominal contents prolapse through the inguinal canal, and it’s more common in draft breeds. This is the main reason we'd do a Closed castration, as it ties off the tunic; but it does increase the risk of infection. Eventration usually involves some fatty tissue (the omentum) and although it needs urgent surgical repair, it isn't usually life threatening. Very occasionally, however, it progresses to evisceration, where loops of intestine come through. This is very serious, but (touch wood) it’s also very rare.
infection is uncommon, and usually responds to antibiotics. In a few unlucky cases, though, a schirrous cord forms, where abscesses form in the canal. These take months of management, and in the end, treatment is usually surgical removal of the infected tissue.
These complications are very rare, and even if they occur, they're usually fixable, so don't get scared of the possibility! I only mention them so you've got an idea of what to look out for.
The last thing to bear in mind is that the gelding may still show sexual interest for some weeks after castration (at least, if he was before), and may even be fertile for a time: although he can't make more sperm without testicular tissue, there will still be some "in storage" in the spermatic ducts. I always advise that a newly gelded colt or stallion should be isolated from mares for at least 6 weeks, after which any remaining sperm will have died or been flushed out, and his testosterone levels will have declined to the point where he won't have any hormonal urges.
The bottom line is this: although it doesn't seem a nice thing to do, for most colts in most situations, gelding leaves them happier and more content than they would otherwise be as entire stallions.
We routinely sedate horses in practice - after vaccination, it’s probably the most common "routine" job that we do. So, what are we doing? How do the drugs work - and why doesn't it always happen the same way?
"Sedation - a state of rest or sleep... produced by a sedative drug."
That's the dictionary definition, and it makes it sound lovely and simple - give a drug, and the patient goes to sleep. Of course, in reality (as usual with anything equine!) life isn't that easy...
For those who haven't seen it before, a sedated horse doesn't lie down, but their head gets lower and lower, and they may require something to lean on to help them balance. It’s also important to remember that a sedated horse CAN still kick - they're just much less likely to do so! It often seems that the horse is still more or less aware of what's going on around them, but they're too sleepy to care about it. As a result, we'd almost invariably use pain relief and local anaesthetic as well if we're carrying out a surgical procedure.
There are a wide range of situations in which we like to use sedation. Generally, it’s to make the horse more amenable when something nasty or scary is being done to them. Of course, this varies from horse to horse. There are quite a lot of horses out there that need a sedative before the farrier can trim their feet; and there are others that will allow you to suture up a wound without sedation or even local anaesthetic (not recommended, but occasionally necessary).
Probably the most common reasons we sedate horses for are...
1) Stitching up wounds, to stop the horse wriggling!
2) Tooth rasping, especially when using power rasps and dremels
3) Some surgical operations - for example, many vets prefer to castrate colts under standing sedation, rather than a general anaesthetic. This is because sedation is much safer than a general anaesthetic... On the other hand, the surgery is easier and safer (for the vet, as well as the horse) if the patient is completely "out", so it comes down to the type of horse and the preference of the vet doing the op.
It’s important to remember that all sedatives temporarily alter the way the horse's brain and body works, and have a serious impact on the heart and circulatory system. As a result, they're all prescription-only medicines, and your vet will want to satisfy themselves that the patient doesn't have any underlying heart problems etc before using them. Overdose of a sedative is rarely fatal in a healthy horse, but it can still be dangerous, especially if there is any underlying illness that makes them less good at maintaining their blood pressure. Its also vitally important to tell your vet the horse's whole medical history if you're asking them to give a sedative - there have been cases of horses who were being treated with a (very safe) antibiotic (TMPS); the owner forgot to tell a vet this, and the combination of sedative and this antibiotic has resulted in a heart attack (technically, a fatal arrhythmia).
There are three routes by which we normally give sedation:
1) By syringe or in feed.
This is the slowest, least powerful and least reliable way to sedate a horse, but it has two advantages - you don't need a vet to come and do it, and you don't need to get so close to the horse to give it.
The drug most commonly used is ACP, sold as Sedalin or Relaquin paste. Occasionally ACP tablets are used, although there are strict restrictions on when a vet is allowed to prescribe tablets instead of paste. There is a newer drug now available as a syringe, detomidine (sold as Domosedan gel), which is absorbed across the membranes in the mouth so shouldn't usually be given with food, but does work faster and give better sedation than ACP.
2) By injection into the muscle.
Many injectable sedatives can be given into the muscle - this injection is more reliable than by mouth, but requires much higher doses than if given into the vein (in my experience, you need 4-5 times as much, and it takes about twice as long to work). It’s only usually needed if the horse is too wild or dangerous to get a vein, but it’s quite useful to "take the edge off", and then I can top up with intravenous sedatives if needed. The other situation where I've occasionally used it is when a severely colicing horse has to take a long ride in a box to get to a surgical centre. In these cases, I have sometimes given the driver a preloaded syringe so that if he horse freaks out or goes crazy in transit, they can give it something to calm it down and relieve the pain until they arrive.
3) By intravenous injection.
Intravenous sedation is by far the best option if possible - it works fast (usually 5-10 minutes), you need lower doses, and you get much better sedation than by any other route. This is what I'll be concentrating on below.
There are three "families" of drugs used to sedate horses:
This is a very "dirty" drug, in that it affects a wide range of body systems. It can only produce mild to moderate sedation on its own, and the effects are very variable between horses. It’s important to remember that once sedation has been achieved; increasing the dose WON'T result in deeper sedation, just more side effects. It also has no painkilling properties.
There are two side effects in particular that we as vets watch out for with ACP. Firstly, it can lead to significant drop in blood pressure, because it makes peripheral blood vessels dilate (this is why it’s sometimes used in laminitis). The second effect is much more interesting - ACP is a mild muscle relacant of some muscle types, so it can be useful in azoturia and choke. There's one exception though (male readers of a senstive disposition, look away now...): ACP is a very powerful relaxant for the retractor penis muscle. This is the muscle that holds the penis in the sheath, and even low doses of ACP usually lead to male horses "dropping" the penis. This can be useful, but unfortunately in some horses (especially stallions, with a larger and heavier penis than most geldings); the paralysis of the penis can be quite prolonged, which can result in penile trauma. In extreme cases, this can be permanent or lead to gangrene, requiring amputation. Bottom line - if at all possible, avoid using ACP in stallions and entire colts!
ACP does, however, have a place in sedation - when mixed with other drugs, it often prolongs sedation and means that the doses of each part of the combination can be dropped, reducing the risk of side effects.
A quick note on ACP tablets - under the current Veterinary Medicines Cascade laws, it is illegal to use ACP tablets instead of paste in horses unless the vet has a clinical reason (unfortunately, price isn't considered good enough) to think that they are more appropriate. As a result, if your vet refuses to give you the tablets, they're not trying to rip you off - they're just obeying the law.
Although opiates on their own are only very weak sedatives in horses, when combined with other drugs they lead to much deeper and smoother sedation than any other drug on its own. The drug usually used is butorphanol, which is a synthetic opiate (it’s a mu/kappa agonist/antagonist related to buprenorphine, for anyone interested) that has a fairly good painkilling effect as well as potentiating sedation from other drugs. Fortunately, it also has very few side effects, although its worth bearing in mind that any other opiates (e.g. Pethidine or Fentanyl) that the horse is given up to about 8 hours later won't work quite like they're supposed to, as the butorphanol will partially block their activity.
These really are the mainstay of sedation in horses (and in dogs and cats, for that matter). Alpha-2 drugs act by tricking the body into thinking it's produced too much adrenaline, so it stops releasing it, resulting in reliable deep sedation. They're also pretty powerful painkillers.
There are three drugs that are commonly used, with slightly different properties. Detomidine and Romifidine are both fairly long acting drugs (30-40 minutes after i/v use), and when mixed with butorphanol are the standard sedative preparation for intravenous use, or on their own into the muscle. Detomidine is also available in a syringe for oral use.
The third drug is xylaxine; this is a bit different in that it gives milder sedation, and only lasts 20 minutes or so. It’s particularly useful for sedating horses for nerve blocks etc, where in half an hour they need to be completely recovered and able to trot up.
Before I sedate a horse, I always have a good listen to the horse's heart, and check its pulse and colour to make sure its cardiovasclar system is healthy. I'll then double check it’s not on any medication, and then give i/v sedation.
I like to use either detomidine or romifidine mixed with butorphanol for routine sedation - I personally prefer detomidine, but that’s probably just because it’s what I "grew up" as a vet using! For longer lasting procedures, or if I want muscle relaxation (especially for dentals where I want the tongue nice and floppy!), I add ACP into the mix.
Dosage is incredibly variable between horses and experience and judgement is more important than all the book learning available. As a rule of thumb, the bigger the horse, the less sedative per kilo of body weight it needs (so Shetlands often need as much as a light hunter). In addition, it depends on temperament - the more highly strung or excited, the more sedatives are needed. The other thing to remember is that apparently identical horses, in the same circumstances, may react very differently - the dose that will have Alf so deep his head's on the floor will have Brutus untouched, while Charlie is in the "Goldilocks" zone where he's just right. Of course, it also depends how deep the sedation you want - although personally, I've found that if you aim for "light sedation" to start with, you usually end up having to top the horse up halfway through.
Once the injection's been given, it is VITAL to give the horse time for it to work in a quiet, dim, calm place. If the horse gets excited while you're waiting for the sedative to kick in, it won't work well. This is doubly true for oral sedatives, but it applies to injections as well.
During the procedure, its sometimes necessary to top up, which is fine - the great thing about the drugs we use is that they work fast enough i/v that you can monitor their effects more or less in real time. Recovery is usually rapid and uncomplicated, although it’s important not to let the horse eat anything until it’s completely woken up, or it may choke.
Very occasionally, I've had a horse that refused to wake up, or went too deep. After my first one, I took to carrying the antidote (Atipamezole, aka Antisedan or Sedistop) with me when I sedated sick or old horses. It's very expensive, but it works within a minute or two to reverse the effect of alpha-2 drugs - and once they're reversed, the horse wakes up incredibly fast!
In practice, sedating horses is as much an art as a science, and there's rarely one "right answer" - it depends on the horse, the circumstances, and what you're trying to achieve. The main purpose is to allow us to treat your horse effectively and humanely.
If you are worried about any problems with your horse or pony, please talk to your vet or try our Interactive Equine Symptom Guide to help decide what to do next.