Oestrous Cycle

Seasonally polyoestrous
Long day breeders with a period of anoestrus beginning in late autumn.
Increasing daylight is the most important factor for inducing the resumption of reproductive activity. The first oestrus will usually occur soon after the shortest day of the year.
If constant 14 hours of daylight is provided, the queen will continue to cycle all year round.
Some non-pedigrees have regular oestrous cycles lasting about 3 weeks, but others show no regular pattern.
Duration of oestrus is 7-10 days regardless of mating.

Oestrogen concentrations increase dramatically at the time of oestrus and may double over 24 hours.
The principle oestrogen is Oestradiol 17β.
The rise in Oestradiol 17β corresponds with behavioural oestrus, there are no external signs of pro-oestrus.

The queen is an induced ovulator, so mating is important in triggering ovulation.
There are receptors in the vulva, which are stimualated by copulation.
This results in release of LH fromt he anterior pituitary gland.
Only 50% of queens ovulate after a single mating, because multiple ovulations are usually required for adequate LH release.
The ovulatory LH surge begins within minutes of coitus.
LH peaks within 2 hours, then returns to basal levels within 8 hours.
Further matings before the peak in LH will result in further LH release.
After multiple matings over 4 hours or more, further matings will not result in any further LH release.
- Due to depletion of the pituitary pool of LH, or the pituitary becoming refractory to further GnRH stimulation.
Once significant quantities of LH are reached, all ripe follicles will rupture (all or nothing response).
Occasionally, ovulation will occur in the absence of contact with an entire tom.
- Receptors similar to those in the vulva are found in the lumbar area.
- These can be stimulated if the queen is mounted by other females or castrated cats.

Sterile matings induce ovulation and result in pseudopregnancy.
Progesterone concentrations are similar to those of pregnancy for the first 3 weeks.
After this, progesterone levels gradually fall and reach baseline at 7 weeks.
Oestrus will occur shortly afterwards.
Nesting behaviour and lactation are rarely seen, but hyperaemia of the nipples is as evident as in pregnancy.
Appetite may increase, and fat may distribute to create an increased abdominal size.

Oestrous Cycle - Cat