Estrous Cycle Flashcards
Estrus (noun)
Period of sexual excitability when a female will accept the male for breeding
Estrous (Adjective)
relating to or a characteristic of estrus
Estrous Cycle
Continually polyestrous
Regular estrous cycles throughout the year
NOT responsive to photperiod
Bovine, Porcine, Some Ovine breeds
Estrous Cycle
Seasonal Polyestrous
Regular estrous cycles during part of the year
Responsive to photoperiod
Short Day Breeders: ovine, caprine, cervids
Long-day Breeders: Equine, Feline, Hamsters
Estrous Cycle
Diestrous
Two estrus per year
Domestic Canine
Estrous Cycle
Seasonally Monoestrous
One cycle per year
African breed dogs, bears, wolves, foxes
Bovine Estrous Cycle Periods
Estrus
Metestrus
Diestrus
Proestrus
Bovine Estrous Cycle
Bovine
Estrus
Standing ot be mounted
Lasts 20 hours
Progesterone levels are low
Estrogen levels are falling
Bovine
Metestrus
No longer “Standing”
Ovulation 10-15 hrs after estrus ends
Lasts 3-5 days
CL is being developed
Follicle Growth
1 day after onset of estrus
Concentrations fo FSH decrease after initial surge
Growth of numerous follicles contine
Bovine
Metestrus
Follicle growth Day 2 post estrus
Progesterone concentrations begin to increase
FSH concentrations remain above basal levels
Dominance of growing follicles begin to affect smallest follicles (inhibin)
Bovine Follicle Growth
Day 3 post estrus
Dominant and subordinate follicles secreting estradiol and inhibin
These two compounds are suppressing the growth of other follicles
If the largest follicle was ablated or aspirated, the largest subordinate would continue to grwo and become dominant
Bovine Follicle Growth
Day 4 post estrus
CL size and progesterone concentrations increase substantially
Divergence of largest follicle form subordinates between day 3-4
Subordiante follicles become atretic
Dominant follicle acquires LH receptors
GnRH (exogenous - injected by human) induced LH surge can ovulate the domiant follicle
Bovine Follicle Growth
Day 5 post estrus
Few Corpora Lutea responsive to exogenous PGF2a
GnRH induced LH surge can ovulate the dominant follicle
Diestrus
Period of the CL
Lasts about 12 days
High levels of Progesterone
Bovine Follicle Growth
Days 6-14 post estrus
Neally all Corpora Lutea are responsive to exogenous PGF2a
GnRH induced LH surge can ovulate the dominant follicle if follicle is not too mature
FSH suppressed
Bovine Follicle Growth
Days 15-17
Nearlly all Corpora Lutea are responsive to exogenous PGF2a
GnRH induced LH surge will ovulate the new dominant follicle
Bovine Proestus
CL is regressing
Lasts 2-3 days
Progesterone levels decreaseing
Estrogen levels Increasing
Bovine Follicle Growth
Day 18
CL regression induced endogneously
GnRH induced LH surge will ovulate the new dominant follicle
Bovine Follicle Growth
Day 19 & 20
CL regression induced endogneously
GnRH induced LH surge will ovlulate the new dominant follicle
Equine Cycle is divided into two parts
Estrus
Diestrus
*Anestrus
Anestrus
Complete absence of estrous cycles during short days
Equine
Estrus
Aka “Heat” or “in heat”
Aka Follicular phase of the estrous cycle
Lasts 7 days
THe mare is receptive to the stallions advances
Progesterone levels in blood are low
Estrogen levels in blood are high
LH surge leasts longer in the mare than other species
Estrus Ends abotu 24-48 hours after ovulation
Equine Estrus
Vaginal Speculum Examinaition
During Estrus, progesterone levels are low and the cervix is swollen with relaxed folds which hang down over hte open orifice
Equine Estrus
Teasing
Obvious interest in the stallion, urination, vulva eversion, and squatting
Equine Diestrus
Aka Luteal Phase of the Estrous Cycle
Time of progesterone dominance
Lasts 14-15 days
The mare refuses the stallion
Progesterone comes from the CL
Endogenous PGF2a is secreted by uterus if no maternal recognition of pregnancy by day 13-14
PGF2a causes CL lysis and a rapid decline in progesterone production the last few days of diestrus
Equine Diestrus
Vaginal Speculum Examination
During diestrus, progesterone levels are high and the os cervix is tightly closed and surrounded by firm, well-defined folds
Equine Diestrus
Teasing
Obvious hostility to the stallion, ears back, striking, biting, squealing
Canine cycle is divided into 4 parts
Anestrus
Proestus
Estrus
Diestrus
Interestrus = diestrus + anestrus
Canine Vaginal Cyctology
Evaluating vaginal cytology is an important clinical skill in canine repro management
Use cotton-tipped swab to gently exfoliate cells form the vaginal vault
Decrease estrogen means the bitch is not interested in breeding and the vaginal lining is thin. Vaginal cells are close to the blood supply and very healthy looking
Increased estrogen means the bithc is interested in mating and the vagina needs to “toughen up” and become thicker. The vaginal cells on the surface are now far from the blood supply and are dead
Canine Anestrus
Lasts for a variable amount of time after diestrus ~ 90-150 days
Anestrus is a time of mandatory endometrial repair
Neither male nor female shows sexual interest
the vulva appears normal, not swollen or edematous
Progesterone is at baseline concentrations <1ng/ml
Prolactin secretion by the pituitary may promote anestrus, becuase prolactin inhibitors can be used to terminate anestrus
Canine Anestrus
Vaginal Cytology
Relatively constant
One sees primarily proabasal and small intermediate epithelial vaginal cells
Neutrophils may or may not be present and RBCs are usually absent
Bacteria may or may not be seen
Canine Proestrus
Averages 5-10 days
Males are interested in the female, but female is not interested in males
The vulva is swollen because of estrogen secretion by the growing follicles
THere is serosanguinous discharge form the vulva that results form diapedesis of RBCs through urterine vessels
The most reliable clinical sign of hte onset of proestrus is noting the first day of a bloody vaginal discharge
LH has an increased pulse-frequency
FSH suppressed
Estrogen comes from the growing follicles and peaks at end of proestrus
Testosterone is relatively high at the end of proestrus. This may result from a “backup” in estrogen synthesis. This may result in some masculine behavior by the bitch such as mounting other dogs
Canine Early Proestrus
Similar to bithc in anestrus except, for the presence of varying ninbers of red blood cells
RBCs numerous parabasal cella nd intermediate cells
Neutrophils are common although usually not abundant and bacterai
the background is granual or “dirty”
Canine Mid-proestrus
THe 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
RBC may ro may not be present
The background is dirty or clear
Canine Late proestrus
No neutrophils, RBC are variable background is clear
Greather than 80% of the vagianl cells are superficial cells, with pyknotic nuclei or anuclear superficial celsl
Canine Estrus
Average 9 days
THe make and female are both interested in each other
The estrous behavior results from the abrupt decline of estrogen following the peak in leat proestrus
Canine Diestrus
Time of progesterone dominance
the hormonal events of diestrus are essentially the same in both pregnant and non-pregnant bitches
The female refuses male advances
Progesterone comes form the CL and rises through the first half of diestrus
Endongenous 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
Canine Diestrus
Vaginal cytology
clearly demarcated from that from a bitch that is nearing the end of estrus
within 24-48 hours at the end of estrus the percentage of superficial cells falls to approxiamately 20%, with the remainder of cells usually being intermediate cells
neutrophils occasionally reappear
ovulation happend 6 days ago
Feline
Proestrus
averages 1 day or less
rejects males, but displays rolling, head rubbing, vocalization, crouching
feline
estrus
averages 6 to 7 days
accepts male - deviation of tail to one side and allows male to grasp dorsum of neck
Intestsification of proestrus behavior: rolling, head rubbing, vocalizing, crouching
INDUCED OVULATOR
Induced ovulator
if mating does not occur, LH is not released
Multiple matings results in higher and more prolonged LH release
Ovulation occurs about 50 hours after LH peak
Feline Metestrus
lasts about 1-2 weeks
if not mated and LH is not released - no ovulation occurs and follicles regress during metestrus
If queen does not ovulate - progesterone does not rise above base-line
Stage of Estrous Cycle Determination
Bovine
One time palpation of ovarian structures will NOT determine chates of cycle
Uterine tone differs based on dominate steroid homrone: relaxed with progesterone, turgid with estrogen; not reliable
Progesterone concentration in milk
Estrus detection - standing to be mounted
Stages of estrous cycle determination
bovine
Estrus detection
breed AI 12 hours after first detection in estrus
secondary signs: riding other cows, mud on back, increased activity
Gomer (penile deviation) bull, androgenized cows
Color-change patches or tail-head paint ot indicate riding
Electronic mounting detector
Electronic behavior monitoring
Stage of Estrous Cycle determination
Ovine
Estrus detection:
Ewes are subtle - difficult to detect in estrus
To detect estrus in order to utilize AI - need a vasectomized ram
Stage of estrous Cycle determination
Caprine
Estrus Detection
Does will vocalize more and increased tail wagging
Vulva becomes reddened and vaginal discharge may be noted
To detect estrus in order to utilize AI - need a vasectomized buck
Stages of Estrous Cycle Determination
Equine
One-time palpation of ovarian structures will NOT determine stages of cycle
Serial ovarian palpation of folicle size can be used to determine timing of ovulation
Cervical tone differs based on dominate steroid hormone
Estrus detection - teasing witha stallion
Stages of Estrous Cycle Determination
Equine
Estrus Detection
daily during breeding season
take at least 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
Stage of Estrous Cycle Determination
Porcine
Standing to be mounted
Twice daily is recommended
Boars and females brought to neutral pen or boar is walked next to femal pen
Boar-odor sprays or audio recordings of boar “chant” can be used in absence of a live boar
Handler applies pressure to females back in the presence of a boar - females in heat will stand firmly
Stage of Estrous Cycle Determination
Canine
Estrus detection - most common method for natural mating
Vaginal Cytolog - NOT precise enough to use alone for AI
Serum Progesterone
Stage of Estrous Cycle determination
canine
serum progesterone levels
First rise in P4 >1ng/ml is correleated with LH peak
Ovulation begins 24-48 hours later, and oocytes are fertile 24-48 hours after ovulation
Measure every 2 days starting on day 5 of proestrus
Breed 4-6 days after first rise in P4
Breed first day P4>5-7.5ng/ml
Breed 72hrs after first day P4 >5-7.5ng/ml Frozen semen)
Stage of Estrous cycle determination
Canine
Serum LH
used in conjunction with P4 measurments
Typically measured every day starting on Day 5 of proestrus
There are several rises in LH prior to the ovulatory peak
This assay is not always used
