Oestrous Cycle - Cat

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.

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.

Pseudopregnancy

• 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.