Planning a Feline Breeding:

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Planning a Feline Breeding

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Many variables to consider here...

First: Is the queen/tom capable of breeding?

Have they attained puberty- at least 2.5 kg body weight and exposed to at least 14 hours of light per day, typically 6-9 months in most females; 6-9 months in males, but may be delayed up to 12 months in some individuals, especially if the queen was born early in the year reaching 2.5 kg at a time while daylight hours were long and gradually decreasing rather than queens born later in the year that will reach 2.5 kg when daylight will be increasing.

Is the queen within her breeding season? This may seem like an obvious statement, however to be considered: most females only come into heat during periods of long daylight. They require about 14 hours per day, which will occur in most households although fertility will drop off at points of the year where lesser levels of daylight exist. Some breeds will reach puberty faster than others e.g. Siamese or Burmese as opposed to Manx or some longhaired breeds.

Is the queen too old? Queens may have very long reproductive lives, even exceeding 10 years, but most experience reduced litter size as the queen ages.

The queen's estrous cycle can be split up into 4 components: proestrus/estrus, interestrus or diestrus and anestrus. She may not complete all 4 stages before moving onto the next cycle or going into seasonal anestrus i.e. seasonally polyestrous. In most cases, proestrus and estrus are measured as one stage. The length of diestrus is determined by whether or not a fertile mating took place. Cats are induced ovulators, which means that copulation must occur before ovulation will take place. If the mating was not fertile (e.g. sterile tom) or the pregnancy terminates early, then diestrus will end sooner than if the queen remains pregnant.

The queen's cycle may look something like this:

feline breeding 1

Scenario 1: estrus followed by no mating= interestrus; if there is still enough daylight to return back to estrus, then the queen will repeat estrus and interestrus until mating or anestrus occur.

Scenario 2: estrus followed by unfertile mating= diestrus of short length (40-45 days); this may be followed by a return back to estrus if still sufficient daylight to promote seasonality or anestrus if the season is over.

Scenario 3: estrus followed by a fertile mating that produces kittens(60-72 days)= either a return back to estrus in 7-14 days after a short lactational anestrus is there is sufficient daylight to promote seasonality or entry into anestrus

Scenario 4: after suppression of cyclicity is lifted, the queen returns to estrus at the start of a new season.

Proestrus is a phase, about 0-2 days in length, only observed in small number of queens. It usually blends into estrus and is therefore counted as just the one phase of estrus. Typically queens will rub their head and neck against objects, but will not yet permit breeding by a male.

Estrus can be as short as 2 and as long as 19 days. It begins with behavioral acceptance to mounting by the tom. It can be seen as a queen crouching with her front end pressed to the ground and hyperextension of her back (lordosis). In this way, the queen presents her vulva to the male. Females may also relentlessly vocalize and may be restless in their attempts to solicit affection (petting) from their owners. Very little discharge is noted at this time, but occasionally a scant amount of clear fluid from a slightly swollen vulva can be seen.

Mating with the tom is brief and when successful, elicits a cry from the queen and an "after-reaction" noted as rolling, aggression toward the tom, and genital licking. Mating only occurs during estrus as females are induced ovulators and typically more than one copulatory event is needed to stimulate ovulation.

Levels of estradiol fluctuate between proestrus/estrus and interestrus until enough stimulation has taken place to generate and LH surge from the queen's pituitary gland and subsequent ovulation.

Interestrus is the period of low estrogen and relative non-receptivity toward the male. It may last 8-10 days. When seen together with estrus, it looks like the on and off again "in heat" behavior typical of this species

In the following graph, ovulation would be taking place over a 24-48 hour interval after the LH peak. Oocytes would be most fertile up to 24 hours after ovulation. The 7 day period of estrus is preceded and followed by 8 days of interestrus.

feline breeding 2

Diestrus follows estrus from a mating that resulted in ovulation. Note that there are some cases of spontaneous ovulation in cats (up to 30-35 % of queens) and also matings that do not result in successful ovulation. In queens, too early a mating or too few copulatory events during the queen's receptive period, may fail to stimulate enough pituitary LH release and subsequent ovulation. The number of oocytes ovulated is also related to the number of matings, in that more matings result in more LH surges, up to a point where the queen will become refractory, and this results in more ovulations. More than one day of exposure to increasing estrogen is required before a queen can release an ovulatory surge of LH, so in this way a single breeding at the onset of her receptive period may not result in pregnancy.

Because the queen can ovulate over a few days, if left to roam free, or left with more than one tom, kittens may belong to more than one sire (superfecundation).

If diestrus does follow ovulation in the queen, levels of progesterone will rise accordingly, while levels of estrogen remain relatively baseline. However, it can be shown that some follicular growth does occur even during pregnancy as the queen can still show signs of estrus. The phenomenon of superfetation (kittens of the same litter of different gestational ages) is anecdotally thought to occur as a result of these estrus periods and subsequent mating during early pregnancy. Although this has yet to be proven, queens who do show estrous activity in diestrus may be susceptible pregnancy loss from the increased levels of estrogen and possible suppression of progesterone.

If the queen is pregnant, diestrus will be maintained until the corpora lutea lifespan is terminated (factors for CL demise still as yet unknown) which is about 65-66 days. Observed gestational length from time of first or last mating has been reported to be as short as 58 and as long as 74 days.

Adding to the mysteries of the queen, it is also possible for queens to deliver their kittens over a period of 1-3 days. If the queen is nervous or stressed, she can interrupt the process of labor after delivery of one or more kittens and still deliver healthy live kittens during a time of day when she feels more relaxed. Most deliveries occur over a shorter length of time (approx 20-30 minutes/kitten)

Prolactin begins to increase mid-gestation in the pregnant queen and rises markedly right before delivery, increasing all the more with lactation and nursing. Without the stimulation of nursing (dead kittens or kittens separated from the queen), prolactin levels will fall within 1-2 weeks.

The following graph depicts diestrus and lactation of a pregnant queen where parturition took place at week 9

feline breeding 3

Some differences between the cat and dog: Unlike the dog, progesterone does not start to rise prior to ovulation and only rises several days post ovulation. Also, progesterone does not have to fall below 2 ng/ml for longer than 48 hours before parturition takes place (some queens have delivered when progesterone was about 5 ng/ml!). Finally, false pregnancy tends to end diestrus earlier than in the non-pregnant state (P4 falls usually around 40-45 days), unlike the dog where false pregnancy tends to extend the time of progesterone influence beyond the typical 58 days of pregnant diestrus. Plasma LH does not increase as the cat is an induced ovulator and is not mating during diestrus (note: see comments on superfetation). Follicular activity does continue throughout pregnancy in the queen, and accounts for some small increases above baseline during pregnancy. If the fluctuation is high enough, it may not only result in signs of estrus, but may possibly result in abortion.

Anestrus is a period of relative endocrine quiescence that occurs at the end of the queen's breeding season. Many other species like deer, horses, sheep and goats are also seasonal. The effects of daylight produce changes at the level of the brain (hypothalamus and pituitary gland) and result in turning on or turning off of reproductive activity. The cat is a long daylight breeder like the horse and so experiences hormonal changes consistent with onset of cyclicity during the period of increasing daylight hours and decreased cyclicity as daylight hours begin to decrease. In the Northern hemisphere, typical breeding season starts in February and continues until September for queens in good body condition. For cats kept indoors, the season can be manipulated through artificial lighting and constant temperature control to ensure cyclicity at various times of the year. They will still experience anestrus at some point- indoor cats with temperature controlled environment but seasonal light still cycle seasonally, but cats with artificial light of 14 hours/day in a climate controlled environment, still experience decreased estrous behavior usually from April to May.

Levels of hormones- estrogen, progesterone and LH would be baseline during this time period.

How is the estrous cycle of the queen manipulated?

1: Artificial lighting programs and temperature controlled environments are the simplest form of control of the seasonal cycle

2: Melatonin supplements to mimic decreased day length may also be used

3: Use of exogenous hormones like GnRH, hCG, FSH and LH can be used to induce ovulation during an estrus period after sufficient exposure to estrogen.

4: Hormones like prostaglandins and anti-prolactin drugs can be used to terminate diestrus early.

Why manipulate the reproductive cycle of the queen?

1: Prevention of mating by artificial stimulation of ovulation (mechanical or hormonal) to induce a short diestrus (40-45 days) to permit breeding at another time.

2: Mismating may have occurred or there may be illness/trauma that would prevent a normal healthy delivery so termination of a pregnancy is desirable. After confirmation of pregnancy at about 20-25 days, hormones to terminate the lifespan of the corpora lutea can be used to shorten diestrus. Pyometra may have occurred, in place of a pregnancy, where it is medically or surgically necessary to intervene.

3: Kittens are desired at times of the year outside of the queen's normal season.

4: Inconsistencies in the queen's cycle preventing normal ovulation during mating.

5: Stressful environment e.g. transportation of the queen causing failure to ovulate.

6: Behavioral mismatch between tom and queen where the desired breeding pair will not mate naturally, but artificial insemination can produce the desired offspring.

7: The availability of the tom/semen is limited e.g. tom now deceased, but frozen semen available.

8: In an aim to avoid/prevent transmission of certain infectious agents e.g. FIV(feline immunodeficiency virus) by use of frozen semen.

9: It is part of the process of advance reproductive technology like In-vitro fertilization, ICSI, and cloning. These techniques are more commonly used in wild/endangered species of felids.

If you have questions about breeding your queen or use of advanced reproductive technologies, please contact our theriogenologist on staff, Dr Mary Sebzda, DVM, DACT. She will be only too happy to answer your questions and assist you in your future plans and goals.

References:

Canine and Feline Theriogenology. S Johnston, M Root Kustritz, P Olson. WB Saunders Co., Philadelphia PA, 2001

Recent advances in feline reproduction. S Romagnoli. In Proceedings from the 2006 World Congress WSAVA/FECAVA/CSAVA.

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