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Theriogenology > Estrous Cycle > Flashcards

Estrous Cycle Flashcards

1
Q

Define Estrus

A
  • Noun
  • period of sexual excitability when a female will accept the male for breeding
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2
Q

Define estrous

A
  • Adjective
  • relating to or a characteristic of estrus
    • “estrous cycle” - estrous modifies the nown cycle
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3
Q

What is continually polyestrous? animal examples?

A
  • Regular estrous cycles throughout the year
    • NOT responsive to photoperiod
  • Bovine, Porcine, some ovine breeds (humans)
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4
Q

What is seasonal polyestrous? animal examples?

A
  • regular estrous cycles during part of the year
    • Responsive to photoperiod
  • Short day breeders: Ovine, Caprine, Cervids
  • Long-day breeders: Equine, Feline, Hamster
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5
Q

What is Diestrous? Animal examples?

A
  • 2 estrus per year - several weeks/months apart
  • Domestic canine
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6
Q

What is seasonally monoestrous? animal examples?

A
  • one cycle per year
  • African-breed dogs (Basinji), bears, wolves, foxes
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7
Q

What are the 4 periods of the bovine estrous cycle?

A
  • Estrus
  • Metestrus
  • Diestrus
  • Proestrus
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8
Q

Follicular growth pattern in cows

A
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9
Q

What is Estrus for cows?

A
  • Standing to be mounted
  • lasts 20 hours (6-30)
  • Progesterone levels are low
  • Estrogen levels are falling
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10
Q

What happens to ovarian follicles on the day of estrus in cows?

A
  • Estradiol positive feedback elicits a surge of LH and FSH
    • LH ⇢ Ovulation
    • FSH ⇢ Starts new follicular wave
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11
Q

What is metestrus in cows?

A
  • No longer ‘standing’
  • Ovulation 10-15 hr after estrus ends
  • Lasts 3 - 5 days
  • CL is being developed
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12
Q

What happens to follicular growth 1 day after onset of estrus?

A
  • Concentrations of FSH decrease after initial surge
  • Growth of numerous follicles continue
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13
Q

What happens to follicular growth 2 days post estrus?

A
  • Progesterone concentrations begin to increase
  • FSH concentrations remain above basal levels
  • dominance of growing follicles begin to affect smallest folicles
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14
Q

What happens to follicular growth 3 days post estrus?

A
  • Dominant and subordinate follicles secreting estradiol and inhibin
    • These 2 compounds are suppressing the growth of other follicles
  • If the largest follicle was ablated or aspirated, the largest subordinate would continue to grow and become dominant
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15
Q

What happens to follicular growth 4 days post estrus?

A
  • CL size and progesterone concentrations increase substantially
  • Divergence of largest follicle from subordinates between day 3 and 4
  • Subordinate follicles become atretic
  • Dominant follicle acquires LH receptors
  • GnRH (exogenous - injected by human) induced LH surge can ovulate the dominant follicle
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16
Q

What happens to follicular growth 5 days post estrus?

A
  • Few corpora lutea responsive to exogenous PGF2a (injected by human)
  • GnRH (exogenous) induced LH surge can ovulate the dominant follicle
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17
Q

What occurs during diestrus of cows?

A
  • “period of the CL”
  • lasts about 12 days
  • High levels of progesterone
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18
Q

What happens to follicular growth 6 - 14 days post estrus?

A
  • Nearly all corpora lutea are responsive to exogenous PGF2a
  • GnRH (exogenous) induced LH surge can ovulate the dominant follicle if follicle is not TOO mature
  • FSH suppressed
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19
Q

What happens to follicular growth 15 - 17 days post estrus?

A
  • Nearly al corpora lutea are responsive to exogenous PGF2a
  • GnRH (exogenous) induced LH surge WILL ovulate the new dominant follicle
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20
Q

What is proestrus in cows?

A
  • CL is regressing
  • Last 2-3 days
  • Progesterone levels decreasing
  • Estrogen levels increasing
21
Q

What happens to follicular growth 18 days post estrus for cows?

A
  • CL regression induced endogenously
  • GnRH (exogenous) induced LH surge WILL ovulate the new dominant follicle
22
Q

What happens to follicular growth 19 - 20 days post estrus for cows?

A
  • CL regression induced endogenously
  • GnRH (exogenous) induced LH surge WILL ovulate the new dominant follicle
23
Q

How many periods are in the Equine estrous cycle?

A
  • Estrus
  • Diestrus
  • *anestrus - complete absence of estrous cycles during short days
24
Q

What is Equine Estrus?

A
  • “Heat”
  • “Follicular Phase of the Estrous Cycle”
  • Lasts ~7 days
  • Mare is receptive to the stallions advances
  • Progesterone levels in blood are low
  • Estrogen (estradiol) levels in blood are high
    • increase followed by decrease
  • LH surge lasts longer in the mare
  • Estrus ends about 24-48 hrs after ovulation
25
Q

How can mares be tested for estrus?

A
  • Vaginal Speculum Examination
    • During estrus, progesterone is low and the cervix is swollen w/ relaxed folds which hang down over the open orifice (external uterine ostium)
  • Teasing
    • Obvious interest in the stallion, urination, vulva eversion (winking), and squatting
26
Q

What is equine Diestrus?

A
  • “Luteal Phase of the Estrous Cycle”
  • Time of progesterone dominance
  • Lasts 14 - 15 days (fairly consistent)
  • The mare refuses the stallion
  • Progesterone comes from the CL
  • Endogenous PGF2a is secreted by uterus if no maternal regognition of pregnancy by day 13-14
  • PGF2a causes CL lysis and rapid decline in progesterone production the last few days of diestrus
27
Q

How can a mare be tested for diestrus?

A
  • Vaginal Speculum Examination
    • During diestrus, progesterone levels are high and the os cervix (external uterine ostium) is tightly closed and surrounded by firm, will-defined folds
  • Teasing
    • obvious hostility to the stallion
28
Q

How many periods are in canine estrous cycle?

A
  • Anestrus
  • Proestrus
  • Estrus
  • Diestrus
  • *Interestrus = diestrus + anestrus
29
Q

How can a bitch be tested for estrus?

A
  • Evaluating vaginal cytology
    • Use cotton-tipped swab to gently exfoliate cells from the vaginal vault (stain w/ Diff-quick)
    • ⇣ Estrogen means bitch is not interested in breeding
      • Vaginal lining is thin.
      • Cells are close to the blood supply and “healthy looking’
    • ⇡ Estrogen means bitch IS interested in mating
      • Vaginal lining becomes thicker
      • Cells on the surface are now far from the blood supply and are dead
30
Q

What is Anestrus in the bitch?

A
  • Lasts for a variable amount of time after diestrus (or whelping) ~90 - 150 days
  • Time of manatory endometrail repair
  • Neither male nor female shows sexual interest
  • Vulva appears normal - NOT swollen or edematous
  • Progesterone is at baseline concentrations (< 1 ng/ml)
  • Prolactin secretion by pituitary may promote anestrus, because prolactin inhibitors can be used to terminate anestus
31
Q

What does the vaginal cytology look like during anestrus?

A
  • Relatively constant
  • Primarily parabasal and small intermediate epithelial vaginal ells
  • Neutrophils may or may not be present and RBC’s are usually absent
  • Bacterial may or may not be seen
32
Q

What id proestrus in a bitch?

A
  • Averages 5 - 10 days (range 2-22)
  • Males are interested in the females, but female is not interested in males
  • The vulva is swollen because of estrogen secretion by growing follicles
  • There is serosanguinous discharge from the vulva that results from diapedesis of RBCs through uterine vessels
  • The most reliable clinical sign of the onset of proestrus is noting the first day of a bloody vaginal discharge
  • LH has an increased pulse-frequency
  • FSH is suppressed
  • Estrogen comes from the growing follicles and peaks at the end of proestrus
    • actually the decline in estrogen at the end of proestrus that causes the bitch to show clinical signs of estrus
  • Testosterone is relatively high at the end of proestrus. May result from a ‘backup’ in estrogen synthesis. May result in some masculine behavior by the bitch, such as mounting other dogs
33
Q

What does the vaginal cytology of the bitch look like in early proestrus?

A
  • Similar to anestrus except for the presence of varying numbers of red blood cells
  • RBC’s, numerous parabasal cell and intermediate cells
  • Neutrophils are common, although usually not abundant, and bacteria may be present in small to large numbers
  • background is granular or “dirty”
34
Q

What does the vaginal cytology of the bitch look like in Mid-proestrus?

A
  • First evidence of continued estrogen effect on the vaginal cytology is the disappearance of neutrophils
  • Fewer parabasal and small intermediate cells, more large intermediate and superficial- intermediate cells
  • RBCs may or may not be present
  • Background is dirty or clear
35
Q

What does the vaginal cytology of the bitch look like in Late proestrus?

A
  • No neutrophils
  • RBCs variable
  • background is clear
  • Greater than 80% of the vaginal cells are superficial cells, with pyknotic nuclei or anuclear superficial cells
36
Q

How long does estrus last in dogs? behaviors?

A
  • Average 9 days (range 3 - 21 days)
  • Male and female both interested in each other
  • behavior results in abrupt decline of estrogen following the peak in late proestrus
    • if decline is prevented (exogenous estrogen) bitch will not show signs of estrus
37
Q

What does the vaginal cytology look like in a bitch in Estrus?

A
  • Throughout standing heat the vaginal cytology remains relatively constant
  • No changes to suggest the day of the LH peak or ovulation or the timing of fertilization
  • Superficial cells and anuclear squames account for greater than 80% of the total vaginal cells, often reaching 100%
  • No neutrophils are seen on cytology throughout this phase, RBCs may or may not be present
38
Q

What happens in Diestrus in the bitch

A
  • Hormonal events of diestrus are essentially the same in both pregnant and non-pregnant bitches
  • Female refuses male advances
  • Progesterone dominates
    • Progesterone comes from the CL and rises through the first half of diestrus
  • Endogenous PGF does not appear to be luteolytic in the bitch
  • Exogenous Prostaglandins are luteolytic in the bitch as early as 5 days after the beginning of diestrus
39
Q

What does the vaginal cytology look like in a bitch in diestrus?

A
  • Clearly demarcated from that of a bitch nearing the end of estrus
  • Within 24 - 48 hour period at the end of estrus, the percentage of superficial cells falls to approximately 20% with the remainder of cells usually being intermediate cells
  • Neutrophils occasionally reappear
  • Ovulation is estimated to have occurred 6 days before the onset of diestrus
40
Q

How many parts are in the feline estrous cycle?

A
  • Proestrus
  • Estrus
  • Metestrus
41
Q

What is proestrus like in a queen?

A
  • Averages 1 day or less
  • Rejects male, but displays: rolling, head rubbing, vocalizing, crouching, etc
42
Q

What is estrus like in a queen?

A
  • Averages 6 - 7 days
  • Accepts male
    • deviates tail to one side, allows male to grasp dorsum of neck
  • Intensification of proestrus behavior
    • rolling, head rubbing, vocalizing, crouching
  • Queen is an induced ovulator
    • If no mating - LH is not released
    • Multiple matings result in higher and more prolonged LH release (single mating may not be sufficient to induce LH release)
    • Ovulation occurs about 50 hours after LH peak
43
Q

What is metestrus like in a queen?

A
  • Lasts about 1 - 2 weeks
  • If not mated and LH is not released:
    • no ovulation
    • follicles regress during metestrus
  • No ovulation - progesterone does not rise above base-line
    • Therefore, not the typical progesterone-dominated diestrus characteristic of the non-ovulating portion of mammalian cycles
44
Q

How can one determine the stage of a Bovine estrous cycle?

A
  • One-time palpation of ovarian structures will NOT determine stage
    • CL and CA are present continually
    • Large follicle present most days
    • serial palpation would be useful - not done clinically
  • Uterine tone differs based on dominate steroid hormone
    • Progesterone - relaxed
    • Estrogen - turgid
    • Not Reliably accurate
  • Progesterone concentration in milk (dairy)
    • P4 high(>1 ng/ml) = NOT estrus
  • Estrus detection aids - standing to be mounted
    • Breed (AI) 12 hours after first detected in estrus
    • Secondary signs: riding other cows, mud on back, ⤒ activity
    • Gomer (penile deviated) bull, androgenized cows
    • Color-change patches or tail-head paint to indicate riding
    • Electronic mounting detector
    • Electronic behavior monitoring
45
Q

How can the estrus cycle be determined in ovines?

A
  • Estrus detection - very subtle
    • TO detect for AI - nee vasectomized ram
    • Doe will vocalize more and increase tail wagging
    • Vulva becomes reddened and vaginal discharge may be noted
  • One-time palpation of ovarian structures will NOT determine stage of cycle
    • CL not palpable
    • Large follicle present many days of the cycle
46
Q

How can the estrus cycle be determined in equines?

A
  • One-time palpation of ovarian structures will NOT determine stage of cycle
  • Serial ovarian palpation of follicle size can be used to determine timing of ovulation
  • Cervical tone differs based on dominate steroid hormone
    • Progesterone - closed
    • Estrogen - relaxed
  • Teasing
    • Daily during breeding season
    • Take 15-20 minutes
    • Estrus behavior may be suppressed in: maiden mares, timid mares, mares with foals, during inclement weather, or early in the breeding season
47
Q

How can the estrus cycle be determined in procines?

A
  • Estrus detection - standing to be mounted
    • 2x daily recommended
    • Boars and females brought to neutral pen or boar is walked next to female pen
    • Boar-odor sprays or audio recordings of boar “chant” can be used in absence of live boar
    • Handler applies pressure to female’s back
      • females in heat will stand firmly
48
Q

How can the estrus cycle be determined in the bitch? (different methods and how they work)

A
  • Estrus detection - most common method for natural mating
    • bring female to male (male’s territory)
  • Vaginal cytology
    • used with other methods
    • Not precise enough to use alone
    • Onset of diestrus is most precise classification possible w/cytology
  • Serum Progesterone
    • First rise in P4 > 1 ng/ml is correlated with LH peak
    • Ovulation begins 24-48 hours later (ovulating for 24-48 hours) and oocytes are fertile 24-48 hours after ovulation
    • Measure every 2 days on day 5 of proestrus
      • breed 4-6 d after first rise
      • breed first day P4 >5-7.5 ng/mL (& again 24-48 hours later)
      • breed 72 hours after first day P4 > 5-7.5 ng/mL (frozen semen)
  • Serum LH
    • used in conjunction with P4 measurements
    • Typically measured every day starting on day 5 of proestrus (vaginal cytology or bitch behavior)
    • Several rises in LH prior to ovulatory peak
    • Not always used - $$
49
Q

What is a unique feature of induced ovulators?

A

If ovulation does not occur follicles regress during metestrus

Theriogenology (29 decks)

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