The Ocstrous cycle is the rhythmic cycle of events that occurs in sexually mature non-pregnant female mammals and includes limited periods of sexual receptivity known as oestrus.
The function of the oestrous cycle is:
To produce ova ready for fertilisation by the male spermatozoa
To prepare the female reproductive tract to receive the fertilised ova
To initiate behavioural patterns in the female that indicate to the male that she is receptive to mating To stimulate the female to stand still and allow the male to mate with her.
For the oestrous cycle to achieve the aim of a fertile mating, the timing of all interrelated components must coincide. The pattern and liming of the oestrous cycle varies between species - the cycle shown by the bitch is different Io Ihat shown by the queen.
Each cycle is divided into phases of varying lengths. These are:
1. Proestrus - period in which the reproductive tract is under the influence of oestrogen
2. Oestrus - period during which the female will allow herself to lx* mated
3. Metoestrus - also called dioestrus: period during which the tract is under the influence of progesterone
4. Anoestrus - period between cycles during which there is little or no ovarian activity.
During the oestrous cycle simultaneous changes occur in:
The ovary and reproductive tract - includes ovulation
The endocrine system - interaction between the hormones oestrogen, progesterone, follicle stimulating hormone and Iuteinising hormone The animal's behavioural patterns.