Reproductive Cyclicity Flashcards
It is part of Exam 2 and it refers to the cyclicity within animals in order to better understand breeeding
What does Anestrus mean?
period when reproductive cyclicity stops (temporarily)
What is the Estrous cycle?
It refers to the whole reproductive cycle and it means series of predictable reproductive events beginning at estrus and ending at estrus.
What does the estrous cycle allow for females to do? How does it last?
1.It allows non-pregnant females repeated opportunities to get pregnant
2, It is continual throughout adult life (with certain exception of species)
Which animals do not have a continuous estrous cycle as an adult?
Humans, Elephants, Orcas
What are some examples of when an animal is under anestrus?
1.Pregnancy
2.Nursing
3.Season of year
4.Indequate nutrition
5.Stressful environment
6.management conditions
7.pathological conditions
What are other ways to say Estrus?
1.Oestrus
2.Oestrous
3.Oestradiol
What is Estrus?
Period of sexual receptivity (other ways to say it are heat, standing heat, lordosis)
What does the term seasonal animals mean?
It is another way to say “in season?
What are examples of Polyestrus animals?
1.Cattle
2.Swine
3.Rodent
4. Domestic cats
5. Horses
What does it mean to be Polyestrus?
- Means to have uniform, regular cycles throughout year without regard to season
2.Pregnancy Opportunities throughout the year
Which animals are seasonally polyestrous?
1.Sheep
2.Horses
3.Goats
4.Wildcats
Which animals are Monoestrous? (one cycle in a year)
Canines, Foxes, Bears
What does the term seasonal polyestrous mean?
It means clusters of cycles in certain times.
Which animals are examples of short-day breeders?
1.Sheep
2.Goats
3.Elk
4.Deer
When do short-day breeders normally have cycles??
1.They normally have cycles when day length decreases
2. Differences in duration of cyclicity
Which are example of Long-Day breeders?
- Horses
- Wildcats
When do long-day breeders normally have their cycles?
They normally have their cycles when day lengths increase
What species of animals are monoestrus?
1.Dogs
2.Wolves
3.Foxes
4.Bears
What does it mean to be Monoestrus?
1.One cycle per year
2.Duration of estrus lasts several days
3. Domestic canines normally have 3 cycles in 2 years.
What do the peaks of charts normally signify in animals?
The peaks normally signify a cycle
What differs in charts between polyestrus animals and seasonal polyestrus animals (Long day)?
Polyestrus animals have peaks throughout their chart while, seasonal polysestrus (long day) usually have their peaks during spring breeding season.
When it comes to Seasonal short day polyestrus animals, when do they normally cycle?
They normally cycle during Autumn or fall so they have peaks during fall season.
When it comes to monoestrus animals when do they normally have their cyclicity?
Based off the chart of the power point between March-April is when they have their cycle, but I do not think there is a definite month or months.
What are the 2 phases of the estrous cycles called ? Why are they named this?
1.Follicular phase
2.Luteal Phase
3.They are normally named this because it is after their dominant structure on the ovary.
What occurs during the follicular phase?
It is during the regression of the CL to ovulation
2. It is a short phase (20% of cycle)
3. There is also a presence of large growing follicles secreting estradiol.
What occurs during the follicular phase?
1.It is during the regression of the CL to ovulation
2. It is a short phase (20% of cycle)
3. There is also a presence of large growing follicles secreting estradiol.
What occurs during the Luteal phase?
1.It is during the period of ovulation until CL regresses
2. It is a longer phase (80% of cycle)
3. There is a presence of corpus luteum secreting progesterone
4. Follicles will continue to grow and regress but not ovulate.
What is the process of Luteolysis ?
It is the process of CL regression, started by prostaglandin F2α
What symbol does E2 represent?
Estradiol
What symbol does P4 represent?
Progesterone
How does the process of phases of cycle go?
It starts off in the follicular phase, goes into ovulation and then goes into the luteal phase then goes back to follicular phase
How does the estrogen and prostaglandin interact with the phases of cycle?
1.Estrogen when at peak levels occurs during the follicular phase.
2.During Luteal phase it is at its lowest until it reaches the follicular phase again
3.Progesterone which causes Luteolysis is at its lowest when it is in the follicular phase.
4. Progesterone reach its highest points during the luteal phase until it goes back down again during the follicular phase
Which 2 stages are under the Follicular phase?
1.Proestrus (before estrus)
2.Estrus(Right before ovulation)
Which 2 stages are under the luteal phase?
- Metestrus
2.Diestrus
In which order do the stages of the follicular phase and luteal phase occur?
- Proestrus
2.Estrus
3.Metestrus
4.Diestrus
Which one of the 4 stages are the shortest of the phases? Which is the longest?
- Estrus is the shortest
- Diestrus is the longest
After which stage does ovulation occur?
After Estrus, Ovulation occurs.
The ovarian follicle is biggest when?
It is the biggest when estrus occurs, and shrinks after ovulation.
When is CL the biggest?
It is the biggest during Diestrus and shrinks during proestrus.
What occurs during Proestrus? How long does it last? What starts this process?
- It begins when Progesterone (p4) declines due to CL regression and ends at the start of estrus
- Lasts 2-5 days
- Occurs when progesterone declines and estrogen is the dominant hormone (major endocrine transition)
- There is a formation of the ovulatory follicle and estrogen secretion increases
5.The ones responsible for this endocrine transition are FSH and LH
When does Estrus occur and what is it? How long does it last?
1.Estrus occurs between proestrus and metestrus.
2.It lasts hours to days (species dependent)
3.There is the presence of the ovulatory follicle
4.Estrogen drives behavioral estrus.
5.It is related to sexual receptivity+ peak estrogen+ LH surge + ovulation.
What increases in an animal during sexual receptivity?
1.Phonation(sound making)
2.locomotion (increased movement or step)
3. Changes in behavior
What is standing estrus?
1.Animal stays still when pressure is applied or when it is about to be mated with.
2.Indication of acceptance of male for mating
What is Lordosis?
1.Characteristic of arching back
2. Used to indicate proper time of artificial insemination in pigs
How does the process in sows occur? When do you know its ready for mating or pregnancy?
The sows go into lordosis and then it goes into standing heat.
What is metestrus? What occurs in it?
- Metestrus is a period between ovulation & initial CL formation
2.It is when estrogen is starting to decrease and progesterone is starting to increase. - It is during the luteinization of ovulated follicles meaning that both estrogen and progesterone (P4) are initially low.
4.It is when the ovulated follicle undergoes “remodeling” (luteinization) forming the intraovarian endocrine gland or the CL
5.Progesterone levels are not high until peak CL formation (normally on day 5)
What is Diestrus? What occurs during this process?
- It is the longest stage of cycle and period of maximum CL function, normally ends when CL regresses
- CL is fully functional and it sustained by progesterone and LH
- High amount of progesterone prepares the uterus for pregnancy
- If the animal is not pregnant, luteolysis occurs (uterine PGF2α)
Which hormone can help maintain the CL?
LH can help maintain the CL
Which animals have similar mean lengths of the estrous cycle? What are the ranges of their cycle?
21d: Cow (17-24 d), Sow (17-25 d), Mare (15-26 d)
17d:Ewe (13-19 d), Queen (4-30 d)
Which animals have different mean lengths of the estrous cycle? What are their ranges of the cycle?
6 months: Bitch (dog) (3-9 months)
10d: Llama (8-12 d)
15d.Alpaca (11-18 d)
What is the average mean duration of estrus for a cow, ewe, sow, and mare? What are their ranges?
1.Cow: 15h (6-24 h)
2.Ewe: 30h (18-48 h)
3.Sow: 50h (19-96 h)
4.Mare: 7d (2-12 d)
What is the average mean duration of the estrus for the Bitch, Queen, Llama, Alpaca
1.Bitch: 9d (4-12 d)
2.Queen: 9d (2-19 d)
3.Llama: 5d (4-5 d)
4.Alpaca: 5d (4-5 d)
When it comes to the estrous cycle in the Bitch how is it different than other animals?
The estrous cycle in the bitch goes in this order.
1.Anestrus-20 wks (5 months in bitch)
2.Proestrus
3.Estrus
4.Diestrus
(does not have metestrus CL forms too quickly, not really apparent)
What is the difference between domestic bitches and wild canines?
- Domestic bitches have only 2 estrous periods in 3 years due to long
- Wild canines usually have one every year
Why does FSH drop around the proestrus stage?
It drops due to negative feedback from inhibin secreted from developing follicles (granulosa cells)
When does the bitch become receptive to males?
The bitch becomes receptive when estrogen drops and progesterone (P4) begins to rise during estrus
When does ovulation occur in the bitch?
It occurs 2-3 days after the LH surge which tends to go down between proestrus and estrus
When does fertilization occur in the bitch?
Fertilization takes place 2-3 days after ovulation
Why does the bitch not have a defined metestrus (or no metestrus)?
It is because the luteal tissue is formed quickly after ovulation
In the bitch, what does anestrus, and proestrus do?
- Anestrus is 20 weeks long and it shows reproductive quiescence (inactivity or dormancy)
- Proestrus is 9 days and it is when blood tinged vaginal discharge & swelling, large follicles, estrogen increase & peaks before estrus, bitch begins to accept male @ end of proestrus.
For the bitch what occurs in estrus?
- Shortly after peak of estrogen
- LH/FSH peaks early in estrus
- Ovulations is by the 2 or 3rd day of estrus and fertilization is 48-72 hours after
- Delayed fertilization, and allows superfecundation (mating/fertilization to several males -> mixed litters)
5.Progesterone increases in later part of estrus and it indications ovulation status.
For the bitch what occurs in diestrus?
- Both pregnant & non-pregnant bitch are in diestrus
- Pregnancy status does not alter length of diestrus
3.Porgesterone peaks about 15 days after estrus.
What is a non-pregnant bitch considered?
Considered pseudo-pregnant
What is the difference between wild and domestics canids?
1.Wild has one estrus period per year
2. In domestic it is 1-3 estrus periods per year, 4 are possible (occurs frequently from feb to may)
When it comes to the queen which estrous cycle is unique for this species?
Postestrus
What has to be done to the queen in order for them to ovulate?
They need to be stimulated in order for them to start ovulation (normally through mating).
What occurs when the queen has no induced ovulation?
It means no CL formation, so there is no metestrus or diestrus.
When it comes to cats does lactation affect anestrus?
No, it does not affect anestrus since the pregnancy of the cat lasts 60 days.
Progesterone rises due to?
CL formation
For the Queen what is there little evidence of? What type of animal are they when it comes to birth?
- Seasonality
- Tend to be polyestrous (domestic cats)
When it comes to anestrus what is the major cause of it in farm animals?
Nutritionally induced is the major cause
While anestrus is active and the ovaries are relatively inactive, with no ovulation and no CL formation what could be the cause of this?
1.Insufficient GnRH
2.Limited LH/FSH
3. Minimal Follicle Growth
What is an indication of the start of the menstrual cycle?
Menses
What is the order of Folliculogenesis in ovulation?
1.Recruitment
2. Selection
3. Dominance
4.Astresia
Most ovarian follicles undergo Astresia. true/false
True
What is the model used to describe ovarian synthesis & secretion of estrodiol?
2-cell, 2 Gonadotropin model
What prefixes in order can help determine the stages of the follicular and luteal phase?
1.Pro-Estrus
2.Estrus
3.Met-Estrus
4.Di-Estrus
When it comes to the bitch, in what sequence is the estrous cycle?
- Anestrus (not under follicular, luteal phase.
- Proestrus
- Estrus
- Diestrus
What is evolutionary Anestrus driven by?
Driven by environment/ nutritional conditions
What is silent ovulation? What example of animal has this?
1.When there is a first ovulation with no estrus
2.An example would have to be a horse
What is Gestational Anestrus caused by?
It is induced by the inhibition of GnRH caused by progesterone.
Which animals will develop follicles after ovulation, without showing behavioral signs?
Cows and ewes are 2 examples that do not show behavioral signs but ovulate.
Can animals get pregnant during silent ovulation?
Yes, animals can still get pregnant during this time.
When it comes to the CL’s produced during silent ovulation what occurs to the hormones?
P4 or progesterone primes the brain in order for it to be responsive to estradiol (E2)
When it comes to mares how can stallions detect when the mare is ready to be bred while in silent ovulation?
The stallions can detect pheromones from the mares even if the mares are unaware they are in silent ovulation.
When is the animal ready to show estrus behavior again during silent ovulation?
The ovulation after silent ovulation should elicit a behavioral response to show that the brain is now “primed”
What effect does melatonin have in the reproduction cycle?
It can shut down an animal’s reproductive cycle or could start it depending on what type of breed it is (short, long day breeders)
What is a way to get past anestrus in mares?
- Using artificial light
- Changing light or darkness
When melatonin increases what decreases?
GnRH
What also interacts with GnRH in the role of regulating cyclicity in response to daylight?
Kisspeptin plays a role
When there is a longer exposure to light and less darkness what is the difference between short-day breeders and long-day breeders?
- Short-day breeders have their kiss neurons inhibited (held back).
- Long-day breeders have their kiss neurons stimulated (more of a flow)
What must interacted with in order to affect GnRH?
Kisspeptin
When it comes to short day breeders what occurs when it is spring/summer?
The increased light-> Increases firing of retinal nerves-> increasing excitation from SCG-> thus increasing inhibition of the pineal gland-> decreasing melatonin-> decreasing -> decreasing GnRH-> Decreasing FSH and LH -> leading to anestrus
During the decrease of light for short-day breeders what occurs?
Decrease of light-> decreases firing of retinal nerves-> decreasing excitation from SCG -> decreasing inhibition of pineal gland -> increases melatonin -> increasing GnRH -> increasing FSH & LH -> Causing cyclicity.
When it comes to lactational anestrus what occurs within the different species?
Dog: no lactational anestrus but enter it after parturition
Cat: may have lactational anestrus but not in uniform (consistent)
Sow: estrous cycling is suppressed by lactation but, weaning initiates estrus (2-3 days)
Horses: No true lactational estrus, has estrus after foaling
Beef Cows: Delayed 40-60 day post parturition weaning initiates estrus (3-30 days)
What does suckling do to animals?
- LH secretion decreases
- inhibitory effect of suckling decreases over time
- Less than 2 x a day or equal to that will hasten estrus, any more of that or equal to 3 will have no effect.
Suckling 2x a day or less will do what to inhibin and what is the result?
- It will not inhibit LH
- Promotes the return to cyclicity.
What is the theory that potentially affects the lactational anestrus with cows (or animals).
The presence of the baby in any form will most likely speed up the process of returning to cyclicity, the suckling is not the exact answer even when nerves cut off.
What is hallmark?
It is the lack of GnRH from hypothalamus
When it comes to nutritional anestrus what is the process?
Anestrus caused due to decreases energy/protein inctake-> decreased GnRH -> decreased LH/FSH-> inactive ovaries.
When females are suckled they are essentially?
Nutrient deprived which prolongs lactational anestrus, or potentially stops cyclicity.
When it comes to nutritional anestrus why is it difficult to manage for primiparous (first time birth giving) females?
They have strong energy demands for lactation and growth at the same time in young animals.
What is the menstrual cycle?
Period between 2 successive menstrual periods
How long does the menstrual cycle?
Lasts 28 days, ranged from 24-35 days
What is menses (menstruation)?
It is the sloughing (the getting rid of dead skin) of the endometrium
What is the key differences between the menstrual cycle and the estrous cycle?
- No defined period of sexual receptivity
- Menses (endometrial sloughing)
- Timeline to describe this cycle begins with menses- not ovulation.
When it comes to the estrous cycle what is the major differences in it than the menstrual cycle?
- It begins and ends with estrus/ovulation
- Follicular phase is short
- Luteal phase dominates
When it comes to the Menstrual cycle what is the major key differences in it than the estrous cycle?
- Follicular phase occupies half of the menstrual cycle
- Ovulation occurs in between follicular phase and luteal phase
- LH peaks in the middle of the cycle when ovulation occurs, not the end
- There are proliferative and secretory phases of the menstrual cycle
What is the definition of proliferative?
The endometrium sloughs and then increases in thickness due to estradiol.
What is the secretory cycle?
Progesterone and estradiol are produced by the CL causing the endometrium to proliferate and reach its maximum thickness.
In the menstrual cycle what is included in the luteal phase?
The secretory phase in which the secretory activity is increased and it prepares the uterus for pregnancy.
What is Amenorrhea ?
Absence of menses in reproductive age women
What could be potential causes of Amenorrhea?
- Menopause
- Low nutrition
- Lactation
What could be potential causes of Amenorrhea?
- Menopause
- Low nutrition
- Lactation
What is menopause?
It is the depletion of ovarian follicles
What are some examples of those who may have menopause?
1.Females with isocaloric intake
2. Negative energy balance
3. Athletes with sustained high levels of intense training.
What is lactational amenorrhea?
It is prolonged ovarian inactivity, depend on suckling status
What can be the effect of lactation in the form of amenorrhea?
It can form a type of contraception when nutrition is limiting
After how long after does a woman begin to menstruate after birth?
1.70% of lactating women begin cycling within 2 years postpartum in the U.S
2. 5-30% women begin menstruation 12 months post partum
What occurs to women who do not lactate and those who do lactate, what is the difference?
Women who do not lactate begin menstruation sooner than lactating women, there must be other stimuli preventing GnRH release postpartum.
