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General

• 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. 
• Normal 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  

• 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. 

• Proestrus, 
• Estrus, 
• Interestrus, 
• Diestrus or pseudopregnancy, 
• Anestrus.

Click to here on the diagram above to view a PowerPoint on the queen's estrous cycle.

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.

• Click here to view a queen not showing lordosis when stroked.
  Right click on the frame to start.
  
• 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

• Estrus is defined as the period of sexual receptivity.
  Click here to view a queen showing lordosis when stroked.
  Right click on the frame to start.

Click here to see  videos of  queens treading during breeding.

Click here to see  videos of  queens and treading and rolling after breeding.
Right click on the first frame to start.

• 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.
  Summary

• Queens are induced ovulators, ovulating in response to vaginal/cervical stimulation from copulation. 
• Following proestrus and estrus, there are three alternatives in the feline:
  •  1) ovulation does not occur, resulting in a return to estrus in 4 to 22 days (average 9 days);
  •  2) ovulation occurs without fertilization, resulting in pseudopregnancy;
  •  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
  

  

• Ovulation is triggered by copulation or mechanical stimulation of the vagina. 
  • Stimulation of nerves in the vagina causes a reflex stimulation of the hypothalamus via pathways in the spinal cord. 
  • The hypothalamus releases gonadotropin releasing hormone (GnRH) which acts on the anterior pituitary, resulting, in turn, in a release of luteinizing hormone (LH). 
  • LH, then, stimulates ovulation and the development of corpora lutea.
• Ovulation is dependent on adequate LH release. 
  • Both 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.

• Release of LH by the pituitary appears to be in part dependent on the duration of its prior exposure to estrogen. The LH response to copulation, therefore, may vary depending on the day of estrus upon which coitus occur. If vaginal stimulation occurs before day 3 of estrus, the queen may not ovulate.

• Reports have verified that spontaneous ovulation may occur in the queen.
  

Copulations and LH Release

• Multiple copulations result in higher levels of LH in plasma and are more likely to result in ovulation than single matings. 

• The duration of elevated LH in plasma also determines whether ovulation occurs. 

• Frequency of coital stimuli, therefore, is an additional factor to consider in determining the adequacy of coital contact. 

• According to one report, LH decreased to baseline values within 12 to 24 hours after a single mating or after multiple matings at less than a 2 hour interval. Moreover, LH remained elevated up to 38 hours after multiple mating intervals of every 3 hours.
  

• To achieve sufficient LH release then, repeated breeding at a reasonable interval should be encouraged. The LH response to a single mating can vary substantially, and neither single nor multiple copulations can ensure ovulation. To increase the likelihood of ovulation breeders should try to maximize the number of matings and breed on successive days of estrus.
  
  

Time of Ovulation

• 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.