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Animal Production > Reproductive Cyclicity > Flashcards

Reproductive Cyclicity Flashcards

1
Q

What does reproductive cyclicity consist of in mammals?

A

The ESTROUS CYCLE & the MENSTRUAL CYCLE. both types of cycles provide the female w/ repeated opportunities to become pregnant

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2
Q

What happens during the estrous cycle?

A
  • during the estrous cycle, sexual receptivity & copulation are the primary behavioural events
  • if fertilization (pregnancy) does not occur, another estrus cycle begins, providing the female with another opportunity to mate & concieve
  • when fertilization does occur, the female enters a period of anestrus that ends after parturition (giving birth), uterine involution (acquisition of normal uterine size & function), & lactation
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3
Q

What are the three types of cyclicity?

A
  1. POLYESTROUS (uniform distribution of estrous cycles that occur regularly throughout the entire year)
  2. SEASONALLY POLYESTROUS (display “clusters” of estrous cycles the occur only during a certain season of the year)
  3. MONOESTROUS (only 1 cycle per year)
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4
Q

What two phases can the estrus cycle be divided into and how are they named?

A
  1. follicular phase
  2. luteal phase
    named after the dominant structure present on the ovary during each phase of the cycle
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5
Q

what is the follicular phase?

A

the period from the regression of the corpora lutea to ovulation (in general, ~ 20% of the estrus cycle)

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6
Q

What are follicles?

A

dominant ovarian structure

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7
Q

What is estrogen & what produces it?

A
  • produced by follicles
  • the dominant hormone during the follicular phase
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8
Q

What are the follicular products?

A
  • estradiol, inhibin A & B
  • the most important suppressors of FSH
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9
Q

What is the luteal phase?

A

the period from ovulation until corpora lutea regression (~80% of the estrous cycle)

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10
Q

What are the corpora lutea?

A

the dominant ovarian structures during the luteal phase

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11
Q

What is progesterone?

A
  • produced by the corpora lutea
  • the dominant hormone of the luteal phase
  • most important suppressor of LH
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12
Q

How is the follicular phase further subdivided?

A

proestrus & estrus stages

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13
Q

how is the luteal phase further subdivided?

A

metestrus & diestrus

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14
Q

What happens during proestrus?

A

formation of the ovulatory follicles & E2 secretion (~2-5 days)

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15
Q

What happens during estrus?

A

sexual receptivity & peak E2 secretion

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16
Q

What happens during metestrus?

A

CL formation & beginning of progesterone secretion (~2-5 days)

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17
Q

What happens during diestrus?

A

sustained luteal secretion of progesterone (~10-14 days)

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18
Q

When and why does female sexual behaviour occur?

A

during estrus b/c of estradiol hormone causing them to be open to mating

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19
Q

What is the length of the estrus cycle in cows?

A

21 days

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20
Q

What is the length of the estrus cycle in ewes?

A

17 days

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21
Q

What is the length of the estrus cycle in sows?

A

21 days

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22
Q

What is the length of the estrus cycle in mares?

A

21 days

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23
Q

Describe the estrus cycle in Sw:

A
  • in sw, the estrus cycle consists of proestrus, estrus, metestrus, & diestrus
  • polyovular (15-30 ovulations per cycle)
  • polyestrous
  • follicular waves are not documented (we dont know if Sw have them or not)
  • luteolysis - Day 15 -18 (Corpus luteum resistant to PGF2a until ~ day 12)
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24
Q

Describe the estrus cycle in Bison:

A
  • BISON CALVES ARE BORN IN A SYNCHRONOUS PATTERN (APRIL-JUNE) IN THE WILD, suggesting a seasonal reproductive pattern
  • ovulatory season is from late July to Oct
  • same as Bo, wave emergence is linked to FSH surge
  • female estrus cycle is 21 days; estrus lasts 9-28 hrs
  • continuous emergence of anovulatory waves during the ANOVULATORY SEASON (Feb- July)
25
Q

Describe the estrus cycle in Wapiti?

A
  • seasonally polyestrous (short day breeder; winter time)
  • 2-4 follicular waves (2 or 3 most common)
  • estrous cycle is ~18-21 days
  • during short photoperiods, the excitatory pathways are less active. therefore, the inhibition of pinealocytes is decreased. melatonin is synthesized & released during the night. therefore, the inhibition on the pinealocyte is decreased b/c of the longer dark periods. MELATONIN STIMULATES RELEASE OF GnRH & THUS INITIATES CYCLICITY.
26
Q

Describe the estrus cycle in mare:

A
  • mares are seasonally polyestrous (in spring)
  • signals the start of the season by producing GnRH -> stimulates the anterior pituitary -> anterior pituitary produces FSH & LH
  • estrus cycle of 21 days (+/- 3 days)
  • ~ 2 follicular waves
  • estrus usually lasts for 6 days but can be 4-10 days
  • estrus behaviour will cease 24-48 hrs after ovulation
  • if the mare is not pregnant, luteolysis day 14-16
  • during winter months, mares are anestrus
27
Q

What produces GnRH?

A

Kiss neurons in the hypothalamus

28
Q

How do short & long days impact short & long day breeders?

A
  • long days lead to decreased melatonin -> (in the mare, this activates the kiss neurons -> causing release of GnRH -> leading to cyclicity) -> (in the ewe, this deactivates the kiss neurons -> leading to decreased release of GnRH -> leading to anestrus)
  • short days lead to increased melatonin -> (in the mare, this deactivates the kiss neurons -> leading to decreased release of GnRH -> leading to anestrus) ->(in the ewe, this activates the kiss neurons -> causing release of GnRH -> leading to cyclicity)
29
Q

Describe the estrus cycle in Ca:

A
  • consists of proestrus, estrus, diestrus, & anestrus (a period of reproductive quiescence) - there is no metestrus in the dog
  • polytocous
  • monestrous (1-4 cycles per year)
  • seasonal (mostly in Feb to May)
  • follicular waves are not documented
  • luteal phase is similar btwn pregnant & nonpregnant (pseudopregnancy)
30
Q

Why is estrus long in dogs?

A

b/c they only come into heat 1x per year. This is due to natural selection & it gives them enough time to breed.

31
Q

Why is fertilization delayed in Ca?

A

b/c primary oocyte becomes the secondary oocyte before release in most animals, but in dogs the primary oocyte is released prior to turning into the secondary oocyte (this requires time before fertilization can occur)

32
Q

Describe the estrus cycle in Fe:

A
  • stages of the estrus cycle include proestrus, estrus, post-estrus, diestrus, & anestrus
  • post-estrus is a term used to describe an inter-estrus period that follows estrus that has not been induced to ovulate by copulation
  • SEASONALLY POLYESTROUS
  • induced ovulatory (copulation is required for induction of the LH surge)
  • follicular waves are not documented
  • luteal phase is ~60 days in pregnant & ~40 days in nonpregnant
  • proestrus + estrus = 2-20 days
  • anestrus (mated) ~30-90 days
33
Q

What is post-estrus in Fe?

A
  • term used to describe an inter-estrus period that follows estrus that has not been induced to ovulate by copulation
34
Q

What happens in a queen if copulation does not occur?

A
  • queen enters estrus (~ 9 days) every 17 days
  • if copulation does not occur, queen enters a post-estrus phase & comes into estrus again a few days later
  • since the queen is an induced ovulator, when mating does not occur, ovulation does not occur, & a CL is not formed
35
Q

What are the 5 types if anestrus?

A
  1. gestational
  2. seasonal
  3. lactational
  4. nutritional
  5. pathological
36
Q

What is lactational anestrus?

A
  • limits pregnancy until young are weaned
  • resumption of OVULATORY cyclicity is variable among spp
37
Q

Resumption of ovulatory cyclicity in our different common domestic spp?

A
  • SOWS - ovulate 6-8 days after weaning (> or = 6 wks pp)
  • COWS - DAIRY VS BEEF (EX: FIRST WAVE IN THE POST-PARTUM (pp) PERIOD, 2-7 days vs ~10 days) -> distinct effect of suckling of HER OWN calf; prevent suckling -> acute increase in LH pulse frequency , hastening ovulatory cyclicity
  • MARES - “foal heat refers to the 1st estrous cycle that occurs in a mare shortly after giving birth” 6 to 8 days pp (1st ovulation at ~10 days)
  • CAMELIDS - induced ovulators - receptive immediately pp, but no ovulation until after ~14 days
  • WOMEN - resume menstrual cycles after 8-12 months if not lactating or beyond 24 months if nursing, energy balance is also influential.
38
Q

What is nutritional anestrous?

A
  • nutritional anestrus is characterized by an absence of GnRH pulses from the hypothalamus, inadequate secretion of gonadotropins & inactive ovaries
  • feed quality & quantity is important; need for energy-rich supplements
39
Q

How do energy demands differ in primiparous vs multiparous animals differ?

A
  • if giving birth for the first time, likely that animal is still developing themself & will require extra energy for this
40
Q

What is menstruation or menses?

A
  • defined as the sloughing of the endometrium to the exterior
  • during the initial 3-5 days of the proliferative phase the endometrium decreases rapidly in thickness b/c it is sloughed to the exterior
  • w/ rising E3, the endometrium begins to proliferate & increase in thickness
  • after ovulation, the CL produces progesterone that causes further proliferation & initiates secretory activity of the endometrium
  • luteolysis initiates another menstrual period
41
Q

What is the average duration of the menstrual cycle in women?

A

averages 28 days w/ a range of 24 - 35 days

42
Q

How does the menstrual cycle differ from the estrus cycle?

A
  • there is no defined period of sexual receptivity
  • there is a period of endometrial sloughing called menses (menstruation)
  • the timeline for description of the cycle begins & ends w/ menses, not ovulation or estrus
  • ovulation occurs @ day 14 rather than @ the beginning & end of the cycle (like in the estrus cycle)
43
Q

What is the difference btwn a 2 wave & 3 wave cycle in human women?

A
  • IOI - 27 days vs 30 days
  • FSH, E2, LH earlier in 2 wave pattern
  • endometrium developed earlier in women w/ 2 vs 3 waves
  • 68% 2 wave pattern vs 32% 3 wave pattern
44
Q

How is ovarian function manipulated?

A
  • ovarian synchronization (for fixed-time insemination)
  • ovarian superstimulation (for in vivo & in vitro embryo production & embryo transfer, & for controlled breeding management)
  • shortening & lengthening the luteal phase
  • synchronizing wave emergence
45
Q

Shortening & lengthening the luteal phase depends on the status of both… which differs btwn….?

A

both the corpus luteum and the follicular wave which differs btwn 2 & 3 wave patterns

46
Q

How do you shorten the luteal phase?

A

treat w/ PGF2a

47
Q

How do you lengthen the luteal phase?

A

treat w/ progesterone

48
Q

What are ways of synchronizing wave emergence?

A
  1. follicle ablation
  2. estrogen & progesterone
  3. GnRH/LH
49
Q

How do you get more than 1 oocyte per cycle?

A

give a ton of LH to keep the follicles growing & then give FSH to cause release of many follicles

50
Q

What is follicle ablation for ovarian synchronization?

A
  • transvaginal ultrasound/guided ablation of antral follicles results in the emergence of a new follicular wave in approximately 1.5 days by removing the suppressive effects of follicle products (ex: estradiol & inhibin) on FSH release
51
Q

How is estradiol & progesterone used for ovarian synchronization?

A
  • CIDR (CONTROLLED INTERNAL DRUG RELEASE): a device that releases progesterone is inserted into the animal. when it is removed, the follicular wave is synchronized across all of these animals
  • suppression of the follicular wave emergence by estradiol/progestin treatment. estradiol causes suppression of FSH & atresia of FSH-dependent follicles. once the injected estradiol is metabolized, FSH surges & a new follicular wave emerges 3-5 days after treatment
52
Q

How is GnRH used for ovarian synchronization?

A
  • synchronization of follicular wave emergence by GnRH causes ovulation of a growing dominant follicle. this removes the suppression of follicle products on FSH release; FSH surges & a new follicular wave emerges approx 2 days after treatment. however, treatment @ random stages of the estrus cycle results in less than 60% of animals ovulating & if ovulation does not occur, follicular wave emergence will not be synchronized
53
Q

What is superstimulation?

A

aka superovulation, is a technique used in reproductive management to induce the development of multiple follicles. leading to the release of multiple oocytes (eggs) during a single estrus cycle

54
Q

What are the extrinsic factors of ovarian superstimulation?

A
  1. gonadotropins
  2. purity
  3. dose
  4. route
  5. frequency
  6. site
55
Q

What are the intrinsic factors of ovarian superstimulation?

A
  1. nutritional status
  2. reproductive history
  3. age
  4. season
  5. breed
  6. OVARIAN STATUS
56
Q

Starting superstimulation during the presence of a dominant follicle can be less effective, why?

A

If the dominant follicle is already picked, then all other follicles are already dead

57
Q

When to do superstimulation?

A
  • starting during the presence of a dominant follicle can be less effective
  • superstimulatory response would be greater if the treatment was initiated before the selection of a dominant follicle
  • significantly more follicles were recruited, & more ovulations occurred when treatment began on the day of or the day before the follicular wave emergence
  • only 20% (4-5 days) of the estrus cycle is available for initiating treatment @ the time of follicular wave emergence (80% of the cycle is not conducive to an optimal superovulatory response)
58
Q

How does human birth control work?

A
  • prevents ovulation “breakthrough” by giving progestagen (progesterone) (LH suppression)
  • follicle development during oral contraception use in women occurs due to lack of suppression during the “Pill Free Interval” (PFI)

Animal Production (13 decks)

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