- The estrous cycle of the domestic animals is divided into Four phases or periods which blend one into the other.
- These phases are;
- Proestrus– Also known as building a period and begins with luteal regression and end with onset of estrus.- Duration is 2-5 Days.
– There is follicular growth and regression of CL of previous cycle (in polycyclic species).
– Uterus enlarge very slightly.
- Estrus– Endometrium is congested and oedematous- Vaginal mucosa become hyperemic.
– The bitch show external evidence of proestrus with vulval odema and sanguineous vulval discharge.
– The period of acceptance of male.
– The uterine , cervical and vaginal glands secrete increased amount of mucus.
– The vaginal Epithelium and Endometrium become hyperaemic Metestrus congested.
– The cervix is relaxed.
– Ovulation occur during this phase of cycling all domestic species exept in cow where it occurs about 12 Hours after the end of estrus.
– Ovulation is the spontaneous process in all domestic species except in cat , rabbit and camel in which it is induced by the act of coitus.
– During pro-estrus and estrus there is follicular growth in absence of CL and main hormone is estrogen .
- Metestrus- Metestrus is the period from ovulation & formation of CL.- It is ill defined phase.
– The granulosa cell of the ovulated follicle rise to luteal cells which is responsible for formation of CL called as luteinization.
– There is a reduction in cervical, vagina and uterine secretion.
– Post oestrus or metestrus bleeding occurs.
– Cervix is relaxed.
- Diestrus- Longest phase of oestrus cycle.- Fully functional Corpus Luteum.
– High level of progesterone.
– Female do not exhibit sexual receptivity.
– The uterine gland undergo hyperplasia and hypertrophy
– Vaginal mucosa become pale.
– Cervix is constricted.
– Thickening of endometrium.
– Vaginal, uterine and cervical secretion is decreases.
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