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Estrous Cycle

Physiology of the Estrous Cycle The estrous cycle is the time between two periods of estrus or heat. The estrus cycle length varies from 18-24 days, with the average about 21 days for cows.

Physiology of the Estrous Cycle The estrous cycle has two major phases: 1. Follicular Phase. 2. Luteal Phase. Different structures on the ovary are present during each phase and different hormones dominate the phase.


Physiology of the Estrous CycleMajor structures on the ovary are:Follicles: a blister-like structure containing the egg. produces hormone “estrogen”. High amount of estrogen causes the estrous behavior.


Physiology of the Estrous CycleMajor structures on the ovary are:Corpus luteum: a hard yellow structure. produces hormone “progesterone”. is responsible for maintenance of pregnancy.


Physiology of the Estrous Cycle The Estrous Cycle has 4 Stages: Proestrus Estrus Metestrus Diestrus Follicular Phase = Proestrus and estrus Luteal Phase = Metestrus and diestrus


Proestrus Proestrus is the period between regression of the corpus Iuteum of the previous cycle and estrus. It is the period of follicular development.


Proestrus follicle enlarges and estrogen increases vascularity of the female reproductive tract increases endometrial glands begin to grow estrogen levels peak


Proestrus During this period the follicle destined to ovulate grows from a microscopic structure to a large fluid filled, blister-Iike structure 3/4 inch to 1 inch in diameter.

Proestrus Cow: 3-4 days Ewe: 2-3 days Mare: 2-3 days

Estrus Estrus is the period of sexual receptivity. The female will stand to be mount by another cow or is receptive to be mated by the bull Final maturation of the egg and follicle also occurs.


Estrus Continued estrogen production by the developing follicle results in a surge in the release of LH and FSH from the pituitary which stimulates maximum estrogen production by the follicle.

Estrus The high levels of estrogen are responsible for behavioral signs of estrus. They also increase contractions of the reproductive tract to facilitate sperm and egg transport.

Estrus Estrogen also influences the amount and type of fluid produced by the oviducts, uterus, cervix and vagina.

Estrus The stringy, clear mucus discharge seen at estrus is secreted from the cervix and is thought to assist the migration of sperm through the cervix.

Estrus Cow: 8-24 hr Ewe: 24-36 hr Mare: 4-8 days Ovulation normally occurs 10 to 12 hours after the end of estrus.



Metestrus Metestrus is the period immediately following estrus and ovulation. Ovulated eggs are picked up by the oviducts and transported to the uterine horns.


Metestrus estrogen low corpus hemorrhagicum present. uterus contractions subside endometrial glands continue to grow and become coiled

Metestrus Cow: 3-4 days Ewe and Mare: 2-3 days.

Diestrus Diestrus is the most lengthy period of the estrous cycle which is the period of corpus luteum function.


Diestrus The corpus luteum is the dominant structure on the ovary during diestrus. It develops mainly from the granulosa cells lining the walls of the collapsed follicle.

Diestrus The CL reaches maximum size 8-10 days after ovulation. The levels of progesterone in blood parallel the growth of the CL. Maximum levels are reached around day 10 and maintained until day 16-18 of the cycle.


Diestrus Days 16-18 of the cycle are critical to the maintenance of CL function. If the cow is not pregnant, the CL is induced to regress by the release of prostaglandin F2α from the uterus.

Diestrus Cow: 10-14 days Ewe: 10-12 days Mare: 10-12 days

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Estrous Cycle Behavior

Estrous Cycle Behavior Oestrus: Oestrus is the complex of physiological and behavioural signs occurring just before ovulation.

Estrous Cycle Behavior A number of physical and behavioral signs may indicate that a cow or heifer is in or near estrus.

Estrous Cycle Behavior Sign of Estrus Standing for mounting by a bull (heterosexual behavior) Standing for mounting by another cow (homosexual behavior) Mount another female (homosexual behavior)


Estrous Cycle Behavior Sign of Estrus clear and elastic mucous vaginal discharge The cow smell the vulva of other cows

Estrous Cycle Behavior Sign of Estrus Bellowing Increased Activity swelling of a vulva reddening of vaginal mucosa soiling or roughening of hair covering rump and/or flanks


Estrous Cycle Behavior Cows are display strong homosexual tendencies, making estrus detection easy even when bulls are not present. Cows that are not in estrus will mount cows that in estrus.


Estrous Cycle Behavior mounting activity is more frequent when 2 or more cows are in estrus than when a single cow is in estrus. Cows in estrus spend more time walking with less time resting and feeding than when in other periods of the estrous cycle.


Estrous Cycle Behavior Frequency of mounting is higher at night than during the day, possibly because it is closer to the onset of estrus, more mounting will be seen during early morning as compared to late afternoon.

Estrus 18-24hr

Metestrus 2-3day
Diestrus 13-15day
Proestrus 3-4day
Pregnancy 272-290day
Anestrus 60day
21day
polyestrous cycle in cow
Estrus 18-24hr
Pregnancy 272-290day

Influence of the length of day light on the ovary function in mares

Photoreceptors in the eyes
Pineal
Hypothalamus
Anterior pituitary
Ovaries
increasing day light
decreasing day light
neurotransmission
portal system
blood circulation
Melatonin
Melatonin
GnRH
GnRH
Gonadotropine
Gonadotropine


Metestrus 2day
Diestrus 15day
Proestrus 2day
Seasonal Anestrus
21day
Seasonal polyestrous cycle in Mare
Estrus 4-8day
Pregnancy 330-336day
Foaling heat 8-10 day

estrous behavior of mares

7-The vulva will be elongated and swollen with the labia partly averted 8-The erect clitoris will be exposed frequently be contractions (winking)

Metestrus 2day

Diestrus 11-13day
Proestrus 2day
Seasonal Anestrus
17day
Seasonal polyestrous cycle in Ewe
Estrus 1-2day
Pregnancy 145-150day

Signs of estrus In Ewe

Oestrous ewes are restless They seek the ram The vulva is slightly swollen and congested, and there is often a slight discharge of clear mucus More ovine matings occur during early morning and evening.
THE DOE (NANNY) GOAT
The detection of heat in a doe is difficult in the absence of a male goat The vulva shows some evidence of oedema and hyperaemia the tail is wagged from side to side and up and down the doe is restless and more vocal, has a reduced appetite and milk yield, and shows mounting behaviour The presence of the pheromones from the male goat, which can be transferred from the scent gland on to a cloth, will often intensify the signs.

Signs of estrus In Bitch

1-The first indication that pro-oestrus is approaching is the onset of slight swelling of the vulval lips 2-This generally precedes the commencement of bleeding by several days. 3-Labial swelling is progressive during the pro-oestrus period. Bleeding attains its maximum early in pro-oestrus and continues at this level into the early part of true oestrus. 4-sudden darting movements which end in a crouching attitude with her limbs tense and her face alert. She barks invitingly, but as the dog approaches she moves suddenly again .


5-With the onset of oestrus the invitation to coitus is obvious. She stands in the mating position with her tail slightly raised or held to one side. She remains still while the male mounts and copulates 6-she will accept coitus until the end of the period. Bleeding, although reduced in amount generally continues well into oestrus. 7-During the course of oestrus the enlarged labia become softer in consistency. Some labial swelling continues into the first part of the metoestrous phase