Slide 1 Hello and welcome to this lecture on the basic theriogenology of cats.
Slide 2 I m going to review some of the basic aspects of feline reproductive physiology because they are so very important; if you have anything to do with feline practice, a Humane Society or an institution with interests in population control, this lecture will be valuable to you.
Slide 3 How many chromosomes does a cat have? I'm not quite sure why I put this in here except to say that I think it is important for you to know the diploid chromosome number of the species you treat. It's just one of those things you expect your veterinarian to know; like body temperature, pulse and respiration rate. Well, enough of that. You can find this chromosome game on the theriogenology website.
Slide 4 Well I just want to get back to some basic physiology here because it is very important in a clinical setting. As you can see from this diagram, ovarian activity in cats is very seasonal. Look at the rhododendron in the background and remember the three red columns crossing it. These red columns represent the proportion of cats that are pregnant in this particular population at this particular time; and remember rhododendrons only bloom in the springtime. On the righthand side you can see some autumn leaves. Notice how low the proportion of pregnant cats there are at this time.
Slide 5 Obviously there is a very strong seasonal influence on estrous cycles in cats. This turns out to be very important in day-to-day practice when one is left with an ovarian remnant after ovariectomy. In those cases, one only has to deal with estrus behavior in the cat in the long day length periods of the year. At other times, Mother Nature takes over and shuts down the hypothalamic pituitary axis and the ovarian activity. As you may remember, seasonal effects are more profound in some breeds that others. For example this Persian cat will only have ovarian activity for a relatively short period of time during the year but this Egyptian shorthair will tend to have ovarian activity over the greater part of the year. If you had to choose one of these cats as your patient with an ovarian remnant, which one would you choose? I would choose the Persian cat. Just remember, the shorter the hair, the longer the breeding season.
Slide 6 Veterinarians often forget about using vaginal cytology in cats. It is not only useful in dogs! In fact vaginal cytology is easier to interpret in cats than dogs; when there are follicles in the ovaries, there are plenty of superficial cells in the vaginal cytology. When ovarian activity subsides, the vaginal epithelium becomes thinner again and the epithelial cells are parabasal, with big healthy nuclei. The inset is there to remind you that cats do not really have estrous cycles in the conventional sense because estrous cycles are usually defined as the time between one ovulation and the next. In cats, there are periods of ovarian activity and quiescence; sometimes distinct, sometimes coalescing with one another. Whenever there is a period of ovarian activity, the Queen will show estrus. Eventually an ovulation occurs, and there is no further estrous activity for a period of 45 days or so. Because there is no estrous behavior during this time, it has been given the name "pseudo pregnancy". But don't confuse this with pseudopregnancy in bitches where they show signs of lactation, nesting etc. This does not occur in cats.
Slide 7 It is rare to have infertility problems in cats; usually just the opposite. However, if your client wishes to breed cats and wonders why the male doesn t appear to be interested in the female or tries to copulate but cannot, just remember this. First, male cats are very, very territorial so don t expect them to be interested in breeding when they are still checking out the new real estate. Only when they know that they are king of the hill will they start to show interest in the female. I took these photographs and I can tell you this chap seemed to take forever before he became used to this cage where I staged this little sex scene. One thing that may make him a little more comfortable is an elevated stage to which he can retreat after copulation. If you have ever seen copulation in cats you will know why. Immediately after the lightning fast copulation, she writhes about as though you have just injected her with subcutaneous peppermint schnapps. And amidst these post-copulatory gyrations, she will often lunge out and attack the male; stopping just short of devouring him like a praying mantis. No wonder he relishes a safe getaway. It is interesting however that within an hour or two they kiss and make up and go at it again. Repeated copulation is essential for sufficient LH release to induce ovulation. In fact, the queen may allow copulation 20 or 30 times over that many hours. So if ever you are feel that they have
fallen short of numerous copulatory attempts, you can induce ovulation with a low dose of native GnRH. The dose is somewhat arbitrary but I usually use between 10 and 20 micrograms to induce ovulation in cats. Another note on this rather bizarre kind of copulation; if the male is too short, he will be unable to copulate. This is because male felids become so obsessed with the neck-nape grip you see here, that they may not have the body length to be able to copulate at the same time. You wish you could tell them which of the two is more important for conception but of course, they may not listen anyway. You know what cats are like.
Slide 8 This is just a reminder on some facets of feline physiology of pregnancy. First of all, what you see here is pretty much par for the course for feline ovulation rate, perhaps 3 to 5 ovulations. So the four conceptuses you see here are about what you would expect. Queens very seldom have very large litters like some bitches. You will also remember that feline pregnancies are actually a little longer that canine pregnancies; 65 instead of 60 days because conception starts as soon as ovulation occurs, not four or five days later as occurs in bitches. This is because feline oocytes are haploid when they are ovulated. This is not really important for any practical reason I can think of but it is useful for starting arguments about gestation lengths. Actually one argument that may start is that gestation is actually longer than 65 days perhaps 67 or even more. This arises from the fact that cats can copulate over two or three days although they only ovulate when they manage to induce an LH surge. So if you count from the very first copulation you can end up with more than 65 days. If you look at the marginal hematoma here, you will notice that it is dark brown, not dark green as it is in bitches. Again this is not very important, especially if you are color blind.
But you know what really blows me away when I look at this image? It is the fact that feline placentation is about as intimate as canine placentation is; in other words, complete passive transfer of antibodies is possible in cats, just as it is in dogs. Yet, despite this intimacy, the feline uterus involutes at the speed of lightening; allowing her to become pregnant again within 10 days of having her kittens, while she is suckling them! This of course is one reason why there are so many unwanted stray cats in the world. Just visit any animal shelter for proof of this. A bitch could never reproduce this frequently. Remember how slow I told you their uterine involution was?
Slide 9 OK here is some more marginally important information about cats and this is more of novelty than anything else. And that is, the kittens can be born rapidly, one after the other and become entangled in a knot of umbilical cords. I have never seen this myself, I have only read about it and have no idea what mother nature does when we are not there but suffice to say, it may be another good reason to carry a Swiss army knife. Another thing I should mention while I am talking about newborn kittens is the problem of infanticide by the Tom cat. There are varied reports on so I am not sure how much of a problem it is in domestic cats but in wild felids, like lions it is definitely a problem; lionesses and their young cubs steer well clear of the lion, even when he has sired the litter. Now here is something that is for a change, quite important to you as a veterinary student and that is the problem of physiological breaks during the birth of kittens; they may be two or three days long. The problem here is: How do you tell if this is dystocia or a physiological break? This is very difficult to do but it seems prudent to intervene and do a caesarean section if efforts to stimulate the uterus with calcium and oxytocin fail.
To close up the issue of parturition, presume that you have been told in your lectures in obstetrics that dystocia is rather uncommon in cats, involving perhaps 3 or 4% of all births. The interesting this about dystocia I would like to share with you is something I have read but not experienced and that is that cats tend crawl away and hide when they are experiencing dystocia so you should not be surprised to be presented with a cat with dystocia that is quite dehydrated and debilitated. One of the first things you may have to do is to re-hydrate and stabilize your patient. Slide 10 This may give us some insight as to the cause of long intervals between kittens at birth. The two ringed embryos were viable at the time I opened this uterus. Their histopathology revealed no autolysis at all. We know that superfetation (conception during pregnancy) occurs in mink and other animals so why not cats? I have no idea what would have happened if this pregnancy had been allowed to go to term. In mink, the older embryos enter a stage of suspended animation called embryonic diapause until the younger embryos catch up in growth. They are usually all born together.
Slide 11 This image is a segue to introduce the topic of accidents of pregnancy. In this case, the little queen here was pregnant but had sustained a diaphragmatic hernia, allowing the uterus to enter the chest. This is quite unusual. After a hysterectomy, the diaphragm was repaired. It is more common for cats to experience uterine torsion and for the uterus to rupture, releasing a kitten or two into the abdomen. They may be discovered later and pronounced the result of an extra uterine pregnancy. This can occur in humans because of their type of placentation but it is simply not possible in cats.
Slide 12 Let s move on to abortion in cats. By this time you have been inundated with the fact that infections like Coxiellosis (Q fever), Toxoplasmosis, and Chlamydophilosis can cause abortions in sheep and are also a threat to human pregnancies and human health in general. Well I am pleased to tell you that for the convenience of veterinary students, the creator also made these the same problems in cats. So if you think of a square with human and cats in opposite corners and sheep and goats in the others, just throw Coxiella, Toxo and Chlamydophila in the centre and you have the picture. So I guess the take home here is not to allow women with cats to attend to sheep and goats. But if the woman and cat live in a high rise apartment and the cat cannot nip out for a quick mouse, the woman and her baby will be safe of course. So, all joking aside, please be careful when you are attending to any of these domestic animals when they are aborting because that's when they could be shedding sporulated Coxiella burnetii, Toxoplasma tachyzooites and Chlamydophila. With regard to Toxoplasmosis, don't forget that the tachyzooites are just as dangerous as the oocysts shed by cats but perhaps even more so because they can come from anywhere; milk, meat, and of course aborting animals.
Slide 13 The grim reality is that more cats than dogs are euthanized in animal shelters. Fewer cats are adopted from shelters as well; so feline overpopulation is a major problem. A natural place to start of course is with ovariohysterectomy. The first thing I am going to do is to take a shortcut and tell you that all the things I said about prepuberal gonadectomy in dogs, applies to cats as well. Obviously prepuberal gonadectomy has to catch on in many companion animal practices but this is just a matter of time because as new graduates enter practice, the situation will change. What I said about ovariectomy versus ovariohysterectomy also applies in cats, perhaps even more so because pyometra is far less common in cats than dogs. It is also a good idea to do ovariectomies instead of ovariohysterectomies because there is less tissue handling with the former and therefore less chance of the ovarian remnant syndrome. Also there is no pending of tissue in the cervical area so transplantation of ovarian tissue into the inaccessible parts of the abdomen is less likely. We'll talk about the ovarian remnant syndrome in a few moments. Before we leave conventional ovariectomies, I should mention that there are indeed some well established effects of ovariectomy on cats. The first is that there is definitely an association
between ovariectomy, hypothyroidism and weight gain. This may even have links to diabetes mellitus which is also reported to more frequent after ovariectomy. But really, this can be countered with dietary control and is certainly not significant enough to dissuade one from ovariectomizing a cat. I think this just calls for good client communication. With regard to feral cats, there are several programs that have been tried to control this problem but one that shows some promise appears to be the trap/spay and release program for female cats. It is probably not a good idea to trap/castrate and release tomcats because dominance is lost in those males when they have harems. Instead, it may be better to vasectomize these toms and then release them. In this manner, their dominance will be retained and they will continue to breed without producing pregnancies. In many cases they will also induce pseudopregnancy in females that have not been ovariectomized; an added advantage. Actually, it is not difficult to do a vasectomy in a tomcat; as with anything this just requires a little practice. Incidentally, there are no reports yet on the use of zinc arginine in male cats. Obviously this holds great promise in male dogs so it will be interesting to see how things develop in cats. While we are talking about population control, I should tell you that you should not be tempted to use Ovarid or Ovaban in cats. In fact, that goes for all progestogens because they are very prone to induce diabetes mellitus in cats. You are probably aware that diabetes tends to occur in pregnant women under the effect of elevated progesterone levels. This is thought to occur because progesterone stimulates the release of growth hormone and growth hormone in turn increases dependence on insulin. Anyway, the same situation occurs in dogs and cats and that is probably why exogenous progestogens induce diabetes in female cats. Still on the subject of steroids, remember to give the androgens a pass as well. From all the lay press on androgen use in humans you know that they cause infertility but don't forget that exogenous androgens also cause liver degeneration. The same is true in cats, especially cats. As you know from what I've told you about racing greyhounds, exogenous androgens seem to be much safer in dogs. In a nutshell then, don't use either a progestogens or androgens for contraception in cats. GnRH analogs will probably become popular in cats too as time goes by but right now, they are still undergoing clinical trials. Fortunately, they appear to be both safe and effective in cats. So keep your eyes open for GnRH analogs in the near future. To terminate pregnancy in cats, it you can use all the same hormones that we use in dogs. Prostaglandin F2apha is particularly effective and safe in cats and often only a single injection is required to terminate pregnancy. The usual dose is 0.025 micrograms per kilogram, given subcutaneously or intramuscularly. Because of the nature of cats, when they abort their will
usually go into seclusion and eat the aborted fetuses as well as the fetal membranes. So this spares the owner the horror that we experience with the same treatment in bitches. Urinary incontinence is NOT a sequel to ovariectomy in cats.
Slide 14 Now we have to discuss the ovarian remnant syndrome. This is very important for you to know about because you will all probably ovariectomize cats at some time. Some of you may do this many hundreds of times. If you belong to the latter group, there is no doubt that some of your patients will experience this syndrome. When you ovariectomize a cat, remember that the ovary is not covered by an ovarian bursa like it is in bitches. This means that when you handle the ovary you can knock off tiny little fragments, sending them into the abdominal cavity. These fragments can easily implant on the peritoneal surface or on the omentum. There, they will grow and become small functional ovaries; perhaps one, perhaps several and their presence will come back to haunt you. Some months later or even the following year you'll get a call from an owner telling you that the cat you spayed is now in heat. And now you know why! The first thing to do is to have the owner come in so you can do vaginal cytology to see if the owners assumption is correct. Sometimes it won't be correct because it can be difficult to tell if a cat is in heat, especially in the absence of a male. After all, they do not show vulva swelling, a
hemorrhagic proestral discharge or any mucus discharge. Sometimes they only vocalize a little, crouch and deflect their tails and the interpretation of this can be a little subjective. But let's say the vaginal cytology reeks of superficial cells and the owner is dead right; the cat is back in heat. Your first step is to swallow a cyanide capsule. Actually, that won t solve the problem so instead you should explain to the owner that this is an occasional hazard when spaying a cat. Then you should mention that you have a few options available. Your first option is just to leave things the way they are because the cat will never become pregnant and will only be an occasional source of irritation to the owner. She may still attract tomcats and one or two may even get run over in front of her house. The second option is to wait until the cat comes into heat again and to treat her with about 20 or 25 micrograms of GnRH. This will cause her to ovulate and she will stay out of heat for the next 6 to 7 weeks. If she is a long-haired cat you may only have to do this once or perhaps twice a year. If she is a short haired breed you may have to do this more frequently so perhaps he will choose option number three. The third option is to go in and try to retrieve the ovarian remnant or remnants. This is difficult enough as it is, so I recommend you induce ovulation before you do that laparotomy because it is easier to see corpora lutea than the tiny bubble-like follicles. If you find the offending remnant, great; if not you have to go back to option one or two. Next time you might want to be a little careful about the way you handle those ovaries.
Slide 15 Finally, a quick word on pyometra: Cats can, and do get pyometra just like bitches and the diagnostic and therapeutic considerations on the same. However pyometra is not nearly as common in cats as it is in dogs. This is because they do not have a ready-made luteal phase after every estrus period. Of course, only a luteal phase will allow pyometra to develop. It is only when copulation occurs and there is no pregnancy that there is a chance of pyometra. But of course cats are very fertile so luteal phases without pregnancies are uncommon in cats and therefore pyometra is uncommon as well. Occasionally however, cats may ovulate without being bred so it is possible to have a cat with pyometra when it lives on the 17th floor of a high-rise apartment building. Quite often, pyometra will be discovered as an incidental finding during routine ovariectomy and that is exactly what happened in the cases shown above. I remember telling you that this commonly happened to me when I ovariectomized bitches in private practice. The same appears to be true of cats.
Slide 16 Thank you.