Castration of male rats

Nuts, torpedoes, balls... If any male animal can be said to think with its testicles, it would seem obvious that rats are ruled by sexual hormones. Rat testicles have twice the volume of the rat brain! When people see those goolies for the first time they can hardly believe their own eyes. Is it a tumor, or is it really... (blush, blush)? Some rat owners never get used to their outsized outgrowths, but others, like me, are fascinated by them. By how they work when in place, and what happens when male rats are deprived of their family jewels by castration. Guessing all the effects of the sexual hormones from their pouch is a tall order.
Maybe you have re-homed a castrated buck from an animal charity organisation. Maybe you have heard that castration can reduce aggression between male rats. If you want to know the stories of Birk Ball-less and his Brawny Brothers, about Norwegian law concerning castration, to know which changes aggression cause, and to know how the operation is performed, please read on.

Birk Ball-less and his Brawny Brothers

Birk as a pup was a ball of fun: cautious but curious at the same time. He had to think twice before trying anything new, but when he did try he did nothing half-heartedly. No alarm bells rang to tell me there would be problems with him. When he and the more than three months older Frodo hit puberty at the same time, though, they took hormonal conflicts to a new height... They were about the same size and up boxing all the time. If this was not enough they seemed to cooperate to keep the rest of the rats on their toes. Apart from boxing there were marking, fluffed-up fur and rump pushing all over the cage. Tufts of hair settled like snow after each fight. Injuries appeared, which was something I had not seen for my first 2 1/2 years as a rat owner! Oh, all right, Frodo had clawed a couple of rats in the face, but this was an entirely different kind of wounds. Birk was acting in a way that made me notify his breeder of a Situation in progress. More often than not I observed Birk scent marking and chugging along like a locomotive with a belly full of hot coal. I felt I was on constant guard against trouble and I was holding my breath each time I let the boys out to play. Even so, or perhaps because of my tendency to herd them away from trouble whenever I saw it brewing, I never caught any of them red handed after a blood spill. Eventually the puffed up fur became sleek, the feet dragging stopped. Birk was almost his old self again, and I was pleased to know I had kept the knife away from his testicles.

There was a quiet interlude where I could concentrate on Frodo's behaviour. He was up to no good at all, see Frodo's story. At the same time I could see Birk slowly but relentlessly rising in the rat ranks. As he grew he took on the other rats one by one and taught them that he was not a pup anymore. It all happened quietly - I only got to see Birk powergrooming an increasing number of his cage mates behind the ears and in the neck. I realised he was the new Omega rat. As he still weighed 50 g less than my Alpha, I was not worried about the coming dispute just yet. But for some reason or other all my rats started acting strange! All of a sudden every one of them became master groomers. They would clean my nails for me, lick me, come up for a cuddle - and each of them would leave a wet, yellow stripe across my hand. Preferably across where someone else had just left his. Labben, the Alpha, prefered to watch it all from a vantage point on my shoulder. When he had left a few drops of himself on my hand going up, that is...

Birk is a sweater rat, he loves to crawl inside my clothes. I usually wear a T-shirt beneath my sweater because of his claws. One warmish day I was without the T-shirt, I dug him out from Valley High and deposited him on my right shoulder. Labben was occupying my left. This was when Birk got it into his head that he would challenge the boss! The sound of two rats making warning signals while balancing on their hind legs behind my left ear and boxing was a hair rising experience for me too! My name is Lorrain, Alsace Lorrain, and it was me they were fighting about! I enforced an armistice without having any fallen rats, and no blood was spilled. But the next day, poor walk-all-over-me Ulf had a long, fresh cut on his flank behind the shoulder. He was in pain and I rushed him to the vet. It was the third shoulder flank wound in a month, but the first serious one. Even if Birk was a prime suspect, Frodo's candidature was equally strong. However, as all of them had started pee marking I felt that by rights no one should be excluded from the list of possible perpetrators. Ulf could not very well have made the wounds himself (he had been a victim twice), but had he snapped at Labben and pushed him over the ledge? The other rat with a scratch was Mimer. He could still have made Ulf's wounds. Had Mimer become mean, or was Yggdrasil egging towards a battle?

Weeks passed. In the daytime all was quiet in the cage. At night I heard the rattling of rats hurtling down the sides of the cage and hitting the bottom drawer. No wounds, until I found a tiny one on Birk's shoulder. All right, this one was acquitted. Frodo was going through a difficult phase, and I could not believe I had two rats with the same fighting style. I intensified my work with Frodo. Even so it seemed to me there were dark undercurrents in these seemingly quiet wasters. The Rat gang - now called the Venetians after their new Essegi Venezia cage - were fine as long as I stayed close by. If I left the room I risked mutiny. They knew when I was near and ready to break up a fight. And the wounds continued to trickle in, about one each fortnight. They were steering towards a major battle. One in which they wanted no interference! In the middle of all this Frodo developed food aggression and had to be put down. I was hoping for a new calm. I got the calm before a storm. One day I was returning after driving the children to school I heard the ruckus the moment I walked in. It had been a long time since I climbed the stairs as speedily. I barely caught the sight of Birk pushing Yggdrasil - the new Alpha after the death of his brother - off a hammock. Birk himself vas unscathed. Yggdrasil had a long slit in his side... New telephone call to the vet, but thanks to the re-generating superpowers of rat skin the wound closed overnight before I had the appointment.

Ulfs wound before the edges started to gape. I cannot be a 100% sure Birk made it, but it was identical to the one he gave Yggdrasil a couple of months later.

I could not let Birk share a cage with other rats. Even if he had only made that wound it was definitely one to many. I am sure Frodo was jointly responsible, but the casualty list from the latest four months looked bad:

The only damage to Birk had been a superficial scratch. Birk went to jail, that is to say he got a cage all by himself. It seemed to suit him well. I even had to give up allowing him play time with Mimer and Ulf. They needed to be herded away from eachother almost all the time. Yggdrasil was by no means willing to forgive and forget, and Birk considered their fight unfinished business. Even two eight weeks old ratlings were seen as adversaries. He "only" puffed up his fur, turned the babies over and stepped on them, but when this goes on and on it is not a minor matter anymore. As a result Birk became my new baby, being totally dependant on Mother's love and attention. He loved me in return. Oh, what moments of bliss we had, him licking and nuzzling me as I had him in my lap scritching him behind his ears! But to tell the truth, I found it quite demanding after a while, watching him clutch his cage bars and seeing his big eyes begging for attention each time I passed by. When he had an airway infection I realised this could not go on. Most likely the stress would kill him by wrecking havoc with his immune system.

After much debating and research I got an appointment for castrating him with the vet. I did not do so lightly. Birk was just turning a year old, and he had perfectionated his fighting technique. Most people who have written about castration of bucks are very clear about the advantages of an early castration. They also write that surgery should take place before the buck has formed a habit of hurting other rats. On top of this I had just heard several stories of rats that did not make it through the operation. On the other hand I had run out of options. I did not want him to die a lonely and premature death of mycoplasma. My vet had castrated rats before without killing them in the process. She knew what kind of medication my rats could (normally) take, and how much. I finally made up my mind when I was offered another castrate for company in case he needed a companion. Castrated rats cannot always live with their former mates again, even if they become docile and friendly. Sometimes the other males seem to think that they have a girl in their group. This can get rather tiresome to a rat who must suddenly watch his back side all the time...

Birk was castrated on his 1 year birthday. Birthday gift: a new chance. Towards the end of this page you can read a full description of Operation Balls end. (No pictures!) Birk recovered quickly, had no wound abscess, and after a week I could let him join a pre-pubertal male during free-range time. Before two weeks had passed he tolerated all of them. After three weeks he was back in the Venetia cage. He has not caused any trouble since. I have never regretted the decision I made for him.

Enter Birk's brothers Jonathan and Skorpan. I rescued them from their second rescue home with the knowledge that both were sweet with humans and had a reputation of beating up other rats. After a start which seemed to belie their reputation I learned that it was not totally unfounded. They were not all out aggressive, but they were no safe with other bucks, and both did bite seemingly without provocation. Having had such great results with Birk, I was eager to see if castration would solve this problem too. Skorpan, the smaller of the two by 200g totally dominated his huge brother. At the time I decided to castrate him, Jonathan still had not attacked any of my other rats. Hence Skorpan underwent the operation alone. After only two days I began to see the changes. Skorpan had been an adventurous guy, leaping from the large table where my other males are content to stroll about, in order to explore the rest of the house. His escapes came to an end. He now preferred to stay inside a cardboard house on the table top. Jonathan took advantage of his brother’s changed state and became the new Alpha of the two. He behaved as ruthlessly to Skorpan as Skorpan had behaved towards him, but there were no wounds from their dominance displays over eachother. Unfortunately, Skorpan proved to be a real whimp without his testicular hormones. I tried him with a pre-pubertal male, which he ignored until the "baby" reached puberty. Skorpan was terrified of the tiny buck. Then I tried him with two young females who were visiting. Skorpan tolerated the shy one at a distance, but made no overtures to her what so ever even when, presumably, she was in heat. The more sprightly one was more than he could handle, even if she were 200g lighter and just being curious.

I did not wish to castrate Jonathan. Some rats become less fearful after castration, but if Jonathan resembled his smaller brother he would grow more fearful than he ever was. The thought of a panicky, almost 900g buck with a habit of biting did not make me inclined towards a surgical solution. I did not think it would help him integrate with other rats. Most of the time the two of them behaved like great friends. Still, each day Jonathan would have at least one major display of dominance. And then I found a bite mark on Jonathan. I called the vet right away, but before Jonathan could lose his balls he managed to inflict a second bite wound on Skorpan. It was a great relief to me than Jonathan both survived the operation and seemed to adjust well to his new hormonal status.

The net result did not seem too bad: the two of them co-habited without quarreling, and Skorpan was much more calm when he was not being bullied anymore. Maybe, just maybe the castration of both could get them to the point where they could be re-introduced to other rats. After one months of intensive work I did see progress with Skorpan. He was able to spend time in a playground with my most gentle buck. It was a fragile peace. It did not hold if Jonathan could smell the other males on their play things. With Jonathan the introduction to other rats took months, even after the castration...

Summing up: my limited experience with castration tells me that this step is not always advisable. I wish I knew in advance which rats would respond favourably, and which would not. I do not. Skorpan at least would have been better off with his balls on. As I cannot predict if the operation will be for the best, it will remain a second-to-last solution for any problem rats in this house. Although it does make chemical castration as a 3 month test trial seem more interesting... I may be writing of Tardak in the future.

Laws and ethics

In spite of the narcosis and pain medication, the aftermath of castration remains a painful experience for the awakening rat. Nor is narcosis in itself a risk free process. Some never wake up, or wake up only to drift into the final sleep. Add that castration has a permanent effect on health and the mental state of the animal. The tendency to overeat and gain weight is increased. Fat rats are more prone to heart- and circulatory diseases as well as diabetes. Their spatial memory suffers. So how can one defend the removal of the testicles from an ethical point of view?
In 2001 the Norwegian Rådet for dyreetikk - an independent, advisory board on ethics, appointed by Landbruksdepartementet (the Department of Agriculture) - delivered a paper on castration which, among others stated:
(translated by me)
According to the view of the Board it is not right to remove body parts from healthy, normal animals just to make them fit in with production or family life. Therefore castration should be forbidden. However, one must consider the fact that our husbandry necessarily limits certain natural behaviours of the animals. Many adult beasts in the care of humans will never be able to live out their sexual drive. A general rule against castration will not lead to most animals following their sexual instincts, but only that their sexuality is controlled by different means. This control could be a source of considerable frustration for the animal. Undoubtedly, some animals could have a freer and perhaps better life as castrates, for instance, a gelded ox may be let out to graze. If the decisive weight is to be placed on the integrity and concern for the animal, in a specific situation these arguments could be used to support castration, not to suppress the practise.

As examples of when castration could be in the best interests of the animal, the statement mentioned aggression and the ability to move among its own species.

The Law on Animal protection did not follow the advice of the Board, to issue a general rule against castration, but to allow castration when it was considered to be in the best interest of the animal. A castration on a male rat is a surgical procedure that must be performed by a veterinary. Otherwise there is no law against it. Still, many vets will want to know why you wish to castrate the animal. The Law on Animal protection does state that animals should not be made to suffer unnecessarily. Aggression, serious nervous problems, or a practical need to let a male animal co-habit with females are deemed justifiable causes for the operation.

In Norway, castrating rats is not common unless the rat has behavioral problems. Some animal welfare organisations routinely castrate their bucks before re-homing, but castration to prevent urine marking or "buck smell" is uncommon. The ethical consideration is not the only barrier. Surgery is costly. Most rat owners will not want to pay the expense until cheaper solutions have been tried. Cynically, the operation costs more than euthanisation and a new rat pup. Often castrating a rat is more expensive than castrating a cat. The work is the same, but the rat actually require a higher dose of medication than the rat! On the other hand this piece of surgery is not more expensive than removing a large tumor. For male rats with behaviour problems due to overproduction of or abnormal sensitivity to gonad hormones, this cut could be the cure that allows meaningful life.

Rat balls belonging to Labben, a now deceased Alpha. In elderly bucks it is not unusual for the rat to drag them across the floor while walking.

Anatomy of the rat testicles

Rat testicles (testes) are lung, tubular organs connected with the urethra by first the epidydermis and the vas ductus (seminal ducts). The epidydermis are two lumps hanging by the testicles. The semen must pass through them to ripen. If not they are not capable of aiding propagation. Parts of the surface of both the testicles and the epidydermis are covered by a beautiful meandering pattern of fine seminal ducts. Unfortunately I do not have any close-ups. My vet wondered if I wanted to bring home a trophy to display in formalin. I was tempted but knew that the pharmacy would have to order the formalin and that the sample would rot in the meantime. Besides, I suspected my husband and the boys might be made to feel a bit Freudian angst if I had displayed my trophy on the mantelpiece. To make amends I've added a link to Kenyon College which has a photo of an opened rat showing the anatomy. Unfortunately the details are not good enough to catch the beauty of the seminal duct pattern.

The testicles are located under the anal orifice and behind the penis of the male rat. As with the human testicles they depend on a fairly narrow temperature range to produce high quality semen. The rat can regulate their temperature by pulling the testicles into the body. In a fight the testicles can be retracted for protection. The muscle which facilitates the withdrawal reacts to noradrenalin (norepinephrine). Noradrenalin is a stress hormone which the rat produces when preparing for fight or flight. The testicles are also protected by a thick layer of fat all around them.

The testicles not only produce semen. They also produce the hormones testosterone, oestradiol, androstendione, and dehydroepiandrosterone (DHEA). These hormones have such a vast number of different effects on the body that listing them all is not possible. Especially since scientists are still finding new effects. It has been shown beyond doubt that a serious fall in the level of these hormones have a positive influence on certain forms of aggression and anxiety in rats. There are other beneficial effects from lowering the level of gonad hormones in the male rat. There are harmful effects too.

After a surgical castration the testosterone stores in the body fat is gone after only a few hours. The behavioral changes, on the other hand, may take two to three weeks. This is partially because of a storage pool of testosterone esters. This storage pool takes about two weeks to deplete. Secondly, the regulation of the receptors in the brain and other body parts takes time. Another quick drop in hormone level is seen in dihydrotestosterone (gone from blood serum in 6 hour but remains longer in the bladder which contains the semen.)

Some effects of castration

The timing of a castration influences the effect of castrating a rat buck. Rats castrated before puberty and before their bone growth is complete will behave differently and have a more "female" shape than if the operation had been delayed. These changes happen no matter at what age the rat is castrated:

  • Fertility disappears
    Self evident - but it does not disappear right away.
  • Less display of sexual behaviour
    The rats can still copulate, but the interest vanes.
  • Less prone to attack from other rats
    If a castrated male rat receives a new cage mate, the male cage mate is less likely to bite the castrate than an intact buck.
  • Lowered aggression
    Nearly all forms of aggression are reduced. I have seen it written that castration does not cure male rat from killing baby rats. Well, it did not help them all, but the castrated baby killers still had a lower probability of killing babies after being deprived of their torpedoes.
  • Less nervous problems
    Unfortunately this is not true for all rats. Some become more afraid afterwards because the testosterone used to make them feel more brave.
  • Less tendency to scent mark
    Urine marking normally decreases.
  • Lowered blood pressure
    The lack of testosterone leads to a decrease in the number of calcium channels in smooth muscles.
  • Lowered pain threshold
    Castrated rats feel painful stimuli more strongly than intact rats.
  • Less effective burning of fat
    Castrates have a lower level of activity and An increased tendency to gain weight.
  • Changed effect of drugs
    For some reason castrated bucks have less effect of morphia than intact males. Otherwise the castrated rats usually receive a greater effect. Testosterone increases the production of certain liver enzymes (cytochrome P-450 and N-demethylase) that have important roles in the elimination of many drugs from the body.
  • Changed uptake of nutrients
    Castrated rats release less amylase in their saliva. This probably means that they do not break down starch as effectively as before castration. The uptake of long chained fatty acids changes too.
  • Changes in fur quality
    The coat of the castrated rat becomes more wooly.
  • Lowered production of skin oils/tallow,
    The production of skin fats depend on oestrogens and testosterone.
  • Decrease in muscular strength
    The muscle levator ani is affected by the level testosterone.
  • Changed tear fluid
    The tear fluid of castrated males is more like the tear fluid of female rats than intact males.
  • Differences in receptivity of infections
    Castrated bucks are less prone to infection by hookworm than intact ones.
There are bound to be effects that I have not read about, and others that have not been discovered yet.

Castrates feel pain more strongly than intact males.
The medicinal dose for castrates often has to be changed to avoid poisoning or side effects.

Operation Throwing the Balls

Quoting from the Board of animal ethics:
It should be a non-negotionable demand that if an animal is castrated, this should always be performed under anaesthesia and with the added benefit of post-operative pain relief.
(my translation)

As most rat owners never enter the operation room during procedure, there are probably people out there wondering what is happening in there. There is more than one operation technique for castration, but this is the most common one. I had better start by telling that castration is a fairly small and simple procedure. This does not mean that the operation always runs on tracks. In Birk's case, however, it took no more than 45 minutes from he received his anaesthetic injection, until I paid up and took him home. Most vets insist that they keep the rat for a few hours before they are allowed to leave with their owner. My vet says that is mostly done to save the owners the pain of watching an animal die post surgery. She rarely manages to chase the Death of Rats* with a syringe of adrenalin/epinephrine if anything goes wrong. Basically she has stopped trying. Besides, she feels most animals will be better looked after by a stay-at-home mum than at a busy veterinary office.

* Death of Rats is a character from the Discworld books by Terry Pratchett. He has given the rats their own Rat with a scythe.

At the very beginning Birk received narcosis by an injection in his belly.
NB! Already at the start one of the dangers of the operation surfaces. Injections in the abdomen may give rise to internal haemorrhages. A neck injection can be used. Unfortunately my rats become more stressed by a neck injection. After we started injection by the abdomen we no longer need such high doses of medication, and the effect sets in earlier too. As I trust her steady hands, and as my rats are far calmer when I hold them myself than if a stranger were to restrict them, I have chosen the danger of bleeding in favour of the danger of giving too much medication.
Birk told us what he meant of the treatment by immediately dropping a couple of soft raisins and stepping in them. Then I put him in his traveller cage to calm him down, and to wait for the deep sleep of narcosis.

When Birk no longer reacted to having his ears touched, nor the closing of his eyelids he was ready. I put him on his back on a special pillow, with his tail against the veterinary. First he was shaved around the operation area and the field of operation was drenched in spirits.
NB! The second peril is cooling. Some narcosis inducers affect the ability to regulate body temperature. In any case the spirit will require energy to evaporate, and the operating table is at room temperature. The pillow is used to lessen the loss of body heat during the operation.

Birk had Simplex eye ointment (a vaseline oil based product) to prevent his eyes from drying up. The vet cut a hole in a small paper operating towel so that she could fasten it around his balls. The paper was fastened with clips to the skin of his belly. Then the vet put one hand on his abdomen to push the testicles downwards into his pouch. slik at hun kunne tre det rundt ballene til Birk. Papiret ble festet med klemmer til mageskinnet hans. With the other hand she cut a small incision in the skin over each testicle before she anchored it with a kind of forceps that could be locked in place.
According to vet this is a place where things can go seriously wrong. If the testicles disappear into the body they are not easy to retract!

With one testicle fixated she could concentrate on the other: pulling it out by the opening while she was loosening the thin membranes around it. Next came tying catgut above the place to cut. The organ was so much longer than I had ever imagined!
NB! Tying off the testicle is probably the second most critical point during the operation, next to proper management of the anaesthesia. If the thread is not tight enough, or slips off, the rat will have internal bleeding and may die.
There are other types of suture thread. Normally the vet would not use catgut, but shortly before the castration she had had to re-operate another of my rats who reacted to her ordinary filament. She was not keen to have yet another re-operation on her hands in case Birk too was allergic, and chose catgut instead.

When the testicle was neatly bound it was cut beneath the ligature. The vet made sure both testicle and epidydermis had come out. Then she repeated the process on the other side.
At last his pouch could be sewn up. The vet made a cross stitch on each side. They would have to be removed after a week, unless Birk had removed them himself by then.
All that was left to do now was cleaning up with a bit of disinfectant. If the operation was a successful one the rat should have lost very little blood, apart from what is already in the testicles. Cleaning up was quick.
This is what my vet uses:
Catgut USP 2/0 EP 3,5 Serrag Wiessner
Prolene 3.0
Domitor vet 1 mg/ml 0,5 ml/kg rat
Ketalar 50 mg/ml 1,5 ml/kg rat

After the operation

Ocular side effects of Ketalar:
Bulging eyes and a milky white spot
Some vets use a second shot to reverse the narcosis. My vet does not. The philosophy is that if the animals sleep for another six hours or so, that is six painless hours without movement. The wounds have a better chance of healing and the rat is less distressed. As a consequence the rat needs a bit more attention in the post-operative phase. I had brought a large, empty glass (formerly holding Dolmio tomato sauce) to the vet's office. Now I filled it with hot water from the tap and wrapped it in an old cloth nappy. This worked well as a hot water bottle for hours. When not in his cage, next to the bottle, Birk slept on my stomach, in a felted wool cloth (boiled woolen sweater). I had to change the cloth a couple of times because he was widdleing himself. I also made sure his eyes remained moist. When the eye ointment had worn away I used viscous tear drops on him every hour. I could have bought the ointment, but with eight rats the single dose packed tear drops are better value. The ointment only keeps for a month after opening.

Birk's eyes looked huge, but I did not think much about it at the time. However, during his next operation I realised I was seeing a side effect of the Ketalar. The bulging eyes meant an increase of the intraocular pressure. Not only that: Birk's normally clear eyes developed a milky white spot: a cataract. Two days later it was gone without a trace.

It is not unusual for a rat to start "snoring" when in narcosis. This has to do with an increase in the secretion of mucus. None of my rats have been greatly troubled by it, but I do watch over them, and change their sleeping position if they become noisy. Usually a new sleeping position is all that it takes to quiet them. I do not know how rats behave if they have been awakened by an injection. All my rats have slept solid for about eight hours (give or take a couple of hours) before the first signs of awakening. It usually starts with small movements around their nose or eyes. Quite often these movements can be seen on and off for a couple of hours before they start crawling around, totally disoriented.

I do not have a picture of Birk waking up. This is his brother Skorpan after his castration. Here Skorpan just managed to drag himself half way inside the wine rack before he collapsed like a drunk.
When Birk started crawling he had very little control of his legs. This is normal. Birk keeled over, slid, and dragged himself around without fully knowing where he wanted to go. If the rat is lying on a bed at this stage it will probably go over the edge. A cage without the possibility to climb is the best solution. Even if a drinking bottle may be difficult for the rat to handle at this stage, do not leave the rat with a bowl of water. Its first action will be to drag itself over to the bowl and fall into it. The rat will become wet and cold, and the stitches will become wet too. In place of a water bowl I usually give the rat a piece of fruit or vegetable with a high water content: a boiled potato, cucumber, water melon... Birk had a bite of a boiled potato that was next to his snout when he woke up. He laboriously crawled the two centimeters, sank his teeth into the spud, probably enjoyed the cool and moist feeling, and went back to sleep without swallowing. I lifted him gently away from the food and got him better bedclothes than a cold potato.

The next stage is when the rat finds out that he can walk again. Birk staggered around with a drunkard's balance and Dutch courage. Having been through this before I did not put him in an ordinary bar cage. He would have tried to climb the bars, definitely lost his balance and probably got a limb stuck in the bars when falling. That is why I use a traveller's cage for a cat or small dog - a plastic shell - for rats who are in the process of waking up. Soft food is still a good idea. I usually do not use painkillers until I have seen the rat swallow anything. After the castration Birk was not interested in dry food pellets for 1 1/2 day, but he lapped up a great deal of yoghurt and porridge. His weight loss was about 45 g during the reconvalescent period. That is more than the weight of the testicles. They are on an average 4,26% of its body weight, that is 21,3g for a 500 gram rat. The weight difference is partly due to the fact that the layer of fat around the testicles, which is removed with them, is not part of the testicle weight. When Birk weighed around 650 g before the castration and ate less than normal for two days, the weight loss seems pretty normal.

Birk did go home with a course of antibiotics. I chose not to give it to him. This was partly because he managed to spit out his entire first dosage. But the fact remains that the testicles and the pouch have an excellent blood supply. Infections are rare. Abscesses are a fairly common complication of the procedure, but reaching an abscess with oral antibiotics is a problem anyway. Had it been a different kind of operation, or a rat in poor health I would not have hesitated to give the medication. As it was, Birk was a model patient. He kept his wound clean, took it easy, and extracted the stitches himself when he felt the wound had knit. He looks a bit odd with those shrivelled, raisin sized appendixes that remain. On the other hand he as stopped using his balls like a dish rag to wipe his urine all over my hands...

Castration is always a calculated risk. The most feared one is the death risk from the medication. For rats with increased risk of haemorrages (Australian/English blue rats) I would not reccommend an intraperitonal injection. Otherwise the procedure above appears to work well. I have had four rats castrated this way without mishap. No deaths, no permanent disability and no wound abscesses!


Statement, Norwegian from Rådet for dyreetikk 2001 about castration
Fulltext Human epididymal proteins and sperm function during fertilization: an update
Abstract Long-lived testosterone esters in the rat
W Borg, C H Shackleton, S L Pahuja, and R B Hochberg
Abstract Changes in Testosterone and Dihydrotestosterone Levels in Male Rat Accessory Sex Organs, Serum, and Seminal Fluid After Castration: Establishment of a New Highly Sensitive Simultaneous Androgen Measurement Method
Abstract Testosterone deprivation by castration impairs expression of voltage-dependent potassium channels in rat aorta.
P Zhou et al.
Abstract Effects of Dehydroepiandrosterone (DHEA) on Pituitary Prolactin and Arcuate Nucleus Neuron Tyrosine Hydroxylase mRNA Levels in the Rat
Ester Garcia De Yebenes et al.
Abstract Territorial aggression of the rat to males castrated at various ages
Kevin J. Flannellya og Donald H. Thor
Fulltext Gender related differences in antinociceptive properties of morphine after gonadectomy in male and female rats
Manzumeh-Shamsi Meimandi et al.
Abstract Castration decreases amylase release associated with muscarinic acetylcholine receptor downregulation in rat parotid gland
Lucila Busch1 og Enri Borda
Abstract Sex differences in hepatic uptake of long chain fatty acids in single-pass perfused rat liver
Michael C. Kushlan et al.
Abstract Hormonal influence on the secretory immune system of the eye: androgen regulation of secretory component levels in rat tears
D.A. Sullivan et al.
Abstract SEX-DEPENDENT DIFFERENCES IN DRUG METABOLISM IN THE RAT II. Qualitative Changes Produced by Castration and the Administration of Steroid Hormones and Phenobarbital
Abstract Experimental studies on the effects in helminthic infection, with special reference to the gonadectomy of the host.
Paik KH.

Matmor original 2008-12-29
last changed: 2009-08-12
Addresse for the main page is: