While some individual aspects of reproductive physiology in the cat are shared with other domestic species, when combined, they set the cat apart as somewhat unusual. Like the mare, the queen is seasonally polyestrous and responsive to photoperiod. Like the bitch, the queen is unusual in maintaining sexual receptivity for a period of some days after ovulation, while the corpus luteum is forming. Most importantly from a clinical standpoint, like the rabbit and ferret the queen is an induced ovulator, requiring a copulatory stimulus or exogenous hormones for ovulation and corpus luteum formation.

Normal Cyclicity of the cat has been determined to be dependent on photoperiod. Cats are "long day breeders" and require 12 hours or more of light to maintain normal cyclicity. polyestrous behavior can be induced by controlling exposure to light. Cyclicity stopped abruptly and folliculogenesis was inhibited in queens exposed to less than 8 hours of light. Cyclicity in the cats resumed an average of 16 days after returning to a 14 hour photoperiod.

Seasonality is more pronounced in cats subjected to natural lighting especially at higher latitudes. Long haired breeds tend to be more seasonal than short-haired breeds, with 90% of long-haired cats experiencing a period of anestrus compared to only 39% of short-haired cats. In an extensive survey of 168 queens, approximately 50% of cats cycled year-round while the remainder experienced a period of anestrus from September to the end of January.

Puberty in the cat usually occurs at 9 to 10 months of age. Puberty may occur as early as 4 months or as late as 2 years, however, because cats are seasonal breeders and the season in which the kitten was born influences the age at which puberty occurs. Kittens born early in the year may be too young to reach puberty before the onset of seasonal anestrus. With the onset of cyclicity the following year, they would be older than kittens born after them the previous year who would be entering puberty with them.

The phases of the feline estrous cycle are identified as Proestrus, Estrus, Interestrus, Diestrus or pseudopregnancy, Anestrus.

Proestrus · Proestrus, the period preceding estrus, lasts 1 to 2 days. This phase is often unobserved and is seen in only 16% of estrous cycles according to one report. · During this time, the female is attractive to but not willing to accept the male. Behavioral changes may begin to be seen during proestrus. The queen may rub against objects, vocalize and assume a lordotic posture. Sometimes referred to as a "dragster posture", she will place her front quarters on the ground, elevate her hind quarters and lift her tail to one side. When the dorsal caudal area is stroked, she will tread with her hind legs.

Estrus is defined as the period of sexual receptivity Estrus lasts 3 to 16 days (average of 7) and then subsides for 3 to 14 days (average of 9 days). Behavioral changes are more pronounced in estrus than in proestrus; however, no conspicuous changes in the appearance or size of the external genitalia are evident. The length of estrus is not affected by breeding or ovulation. Inducing ovulation in a queen in an effort to terminate objectionable estrus behavior will not succeed. It will, however, prolong the interestrual interval and delay the return of the undesirable behavioral display. The period following estrus is affected by ovulation whether induced by copulation or exogenous hormones.

Interestrus Interestrus is the period between successive estrus periods if ovulation does not occur. · If the queen is not bred, she will cycle into estrus on an average of every 2 to 3 weeks.

Diestrus If the queen ovulates, corpora lutea are formed and secrete progesterone. Elevated progesterone levels are the hallmark of diestrus. If the queen is not pregnant, diestrus is also termed pseudopregnancy and lasts for 35 to 40 days.

Anestrus Anestrus is the seasonal period when the cat does not cycle.

Queens are induced ovulators, ovulating in response to vaginal/cervical stimulation from copulation. Following proestrus and estrus, there are three alternatives in the feline: o 1) ovulation does not occur, resulting in a return to estrus in 4 to 22 days (average 9 days); o 2) ovulation occurs without fertilization, resulting in pseudopregnancy; o 3) ovulation occurs and ova are fertilized, followed by pregnancy. Vaginal Cytology is not commonly performed in the queen because it may induce ovulation and it is difficult to interpret.

Ovulation is triggered by copulation or mechanical stimulation of the vagina. oStimulation of nerves in the vagina causes a reflex stimulation of the hypothalamus via pathways in the spinal cord. oThe hypothalamus releases gonadotropin releasing hormone (GnRH) which acts on the anterior pituitary, resulting, in turn, in a release of luteinizing hormone (LH). oLH, then, stimulates ovulation and the development of corpora lutea. Ovulation is dependent on adequate LH release. oBoth the peak concentration and the duration of elevation of LH are important in determining whether ovulation takes place. Insufficient copulatory stimuli will fail to induce enough LH to be released to cause ovulation. LH release occurs within minutes of coitus and peaks approximately 1 to 2 hours later.

Ovulation reportedly occurs 24 to 60 hours post coitus and may vary depending on the mating pattern. Progesterone levels in the blood can be used to verify ovulation. Concentrations of progesterone greater than 1 ng/ml are considered indicative of ovulation. Peak levels of 35 ng/ml in the pregnant queen and 24 ng/ml in the pseudopregnant queen are observed at approximately day 21 post coitus.