Oestrous Cycle - Cat
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- 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.
Mating and Ovulation
- 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.