Feline Infertility

Causes of queen infertility, or inability to produce kittens are varied. Some of the common reasons queens do not get pregnant include:

Irregular or absent cycles

In this case, the queen may not cycle at all, or may have prolonged intervals between estrus—estrus being the heat, the time when she is willing to mate. If readiness for mating is not evident by about 2 years of age, it may mean that she is not going to reproduce normally, or it may mean that she does not show her estrus signs very much, and the estrus is being missed. Some Persians and Persian-related breed queens are very subdued in their signs of estrus. It is also important to note that these longhaired breeds often are late to mature, and it can be 18 months or so before the female starts cycling properly.

Cats not showing normal signs of heat may also be reluctant to do so if they are bottom cat on the social ladder, or if they are housed in overcrowded conditions. Placing them in a smaller group or providing individual housing, increasing light to over 12 hours daily, and feeding them well may help to encourage signs of heat, as will introduction of a breeding tom or another female in heat.

The first few cycles in cats are of suboptimal fertility, so breeding her at this time may not lead to pregnancy. Queens that are older may stop having a regular reproductive cycle, which can lead to infertility or low fertility. After about 8 years of age, fertility will start to drop off.

Queens born with congenital defects of the reproductive tract, or genetic abnormalities such as intersex may be sterile because the tract is not functional due to blockage, or malformation / absence of key structures.

Queens who are chronically ill and in very poor condition (e.g., cancer, chronic virus infection) may not be as fertile. Administration of certain prescription medications may also affect the reproductive hormone balance adversely.

Queens who are experiencing considerable stress (e.g., lots of travel, new environment, cat-to-cat social conflict), or nutritional deficiencies may also experience reduced fertility.

Uterus pathology

The uterus is in need of precise hormone control to maintain normal structure and function. There is a spectrum of changes which occurs if the balance of normal reproduction of regular cycles and pregnancies is interrupted. Cystic endometrial hyperplasia (CEH), endometritis (infection of uterus lining), and pyometra (pus in the uterus) represent this abnormal spectrum of changes.

The CEH condition represents uterus lining overgrowth /degeneration associated with hormone imbalances affecting mostly older queens, and can interfere with her ability to conceive. If the hormones (most commonly the progesterone type) continue to stimulate the uterus, the lining continues to thicken and the uterus becomes prone to infection, thus endometritis, and ultimately pyometra will be sequelae to the CEH. Endometritis may only show up as infertility, but usually pyometra makes the queen quite ill, and she may have a fever, poor appetite, a discharge, be dull, and have a bloated appearance. If the uterus is closed, no discharge may be found and the queen will rapidly deteriorate without intervention. Queens not being used for breeding who are experiencing repeated estrus periods, and ovulating without pregnancy are at high risk for this sequence of events.

Early pregnancy loss

This can be very difficult to pick up. Infections, defects in the offspring, stress, chronic queen illness, or nutritional deficiency (e.g., taurine, copper) may lead to loss early in the pregnancy, such that it might not have been known that she was pregnant.

Breeding management

This is a delicate matter in cats! Some apparent infertility is really just due to insufficient mating frequency occurring during her estrus, or efforts to mate incompatible tom and queen.

Tomcat fertility

Tomcat infertility may also be the source of the problem! If the male has low or absent sperm production, or is incapable of mounting the queen due to rear end discomfort due to arthritis, hip dysplasia, or debilitation, he may be the cause of the lack of pregnancy. Temperament problems, strong mate preference, or being inexperienced or shy may interfere with normal mating behavior. Toms also may develop a penis hair ring, leading to inability to breed.

Getting to the root of reproduction failure in cats requires the assistance of your veterinarian. Tests may be recommended to help determine the problem, and treatment depends on the cause.

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