Estrous Cycle Flashcards
1
Q
Define Estrus
A
- Noun
- period of sexual excitability when a female will accept the male for breeding
2
Q
Define estrous
A
- Adjective
- relating to or a characteristic of estrus
- “estrous cycle” - estrous modifies the nown cycle
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)
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
5
Q
What is Diestrous? Animal examples?
A
- 2 estrus per year - several weeks/months apart
- Domestic canine
6
Q
What is seasonally monoestrous? animal examples?
A
- one cycle per year
- African-breed dogs (Basinji), bears, wolves, foxes
7
Q
What are the 4 periods of the bovine estrous cycle?
A
- Estrus
- Metestrus
- Diestrus
- Proestrus
8
Q
Follicular growth pattern in cows
A
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
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
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
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
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
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
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
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
17
Q
What occurs during diestrus of cows?
A
- “period of the CL”
- lasts about 12 days
- High levels of progesterone
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
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
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
