Lecture 41 (Repro 3) Cyclicity 2 Flashcards
What age do dogs enter puberty?
6 to 9 months
What is the mean interestrus interval in dogs?
7 months
True or false: There is no seasonal influence on the cyclicity of dogs.
True. Dogs are non seasonally monoestrus
Does endometrial sloughing occur in dogs?
No!
What marks day 0 of the canine estrous cycle?
LH surge
What hormone is measured in dogs to determine start of estrous cycle?
Progesterone - indirect measurement (not LH which is the mark of day 0).
In the dog, what are the names of the two estrous stages that make up the follicular phase? How long do these stages last?
Proestrus and estrus (both 9 days long)
What stage comprises the luteal phase of estrous in the dog? How long does this stage last?
Diestrus. 2 months
Estradiol concentration _________ (Rises or falls?) during proestrus in the dog.
Rises
When does estradiol in the dog reach its peak?
24-48 hours prior to LH surge
What causes proestrus bleeding in dogs?
Extravasating of erythrocytes by diapedesis from the hyperaemic endometrium under estrogen stimulation.
Do dogs allow mounting in proestrus?
No! Do not allow this until they are actually in estrus.
What are the earliest cytological finding for proestrus in dogs?
presence of red blood cells and intermediate cells.
What is the only fixed point of the bitch’s Repro cycle?
LH surge
What is flagging (dogs)?
Upon perineal stimulation, bitch will deflect tail
What is lordosis reflex?
Female animal responds to lumbar pressure by standing still and firmly and arching back slightly.
During estrus, how does the vaginal discharge of the bitch change?
From serosanguinous to straw coloured
What are the predominant cells in vaginal cytology during estrus?
Keratinized superficial epithelial cells (psychotic, fragmented or absent nucleus, and an eosinophilic cytoplasm)
On what day will ovulations in the bitch’s estrus be complete?
Day 3
Where is the dog’s oocyte arrested at the time of ovulation? what is the significance of this
Prophase 1 - not fertilizable at this point
On what day will fertilization be complete in the dog?
Day 6
What hormone being secreted in non pregnant bitches can initiate pregnant like behaviour (AKA Pseudopregnancy)
Prolactin
What characterizes the appearance of vaginal cytology in the diestrus stage of the bitch?
Appearance of parabasal and intermediate cells with large number of leukocytes (neutrophils primarily)
About when does P4 (progesterone) secretion peak in the dog’s cycle and what happens after this peak?
15 to 25 days. after this P4 decreases to below 1ng/ml by days 55 to 60 by gradual luteolysis
What compound is the CL susceptible to?
PGF2 alpha (prostaglandin)
Among the following, which physiological process is most reliable for predicting breeding time in the bitch: A) proestrus breeding B) Keratinization of superficial epithelial cells C) Ovulation D) LH surge
D - LH surge
Proestrus bleeding in the bitch is due to
A. the diapedesis of RBC from the endometrium under the
influence of estrogen
B. the diapedesis of RBC from the endometrium under the
influence of progesterone
C. the sloughing of endometrium associated with a decrease
in progesterone
D. the sloughing of endometrium under the influence of
prostaglandins
A. the diapedesis of RBC from the endometrium under the
influence of estrogen
Domestic cats are (what type of estrous cycle) whereas wild cats are (what type of estrus)?
Polyestrus, Seasonally polyestrus
What is induced ovulation?
Mating is required for ovulation occur - the mechanism by which this occurs is the levels of LH increasing as the number of matings increase.
How many matings in cats are required to achieve adequate LH?
4
What happens to the cat’s cycle if copulation does not occur?
The cat enters postestrus phase and returns to estrus later
What species are induced ovulators?
Cat, rabbit, camelids, ferrets, mink
What happens in the diestrus phase of the queen (cat)?
Ovulated cats will develop a corpus luteum and enter either pregnancy or pseudopregnancy
How long does diestrus last in pseudopregnant cats and pregnant cats?
about 40 days for pseudopregnant and about 60 days for pregnant
What type of estrous cycle do equine have?
Seasonally polyestrus (long day breeders)
What gland is associated with seasonally polyestrous animals?
Pineal gland
What does the pineal gland secrete?
Melatonin
What affect does melatonin have on the hypothalamus and when is it synthesized?
Synthesized at night and decreases GnRH content in the hypothalamus
______________(Decreasing or increasing?) Day length reduces the content of GnRH, LH, and FSH
Decreasing
At what point in the year are horses in anestrus?
winter - due to shortest days meaning lowest GnRH content and highest level of melatonin
What is vernal transition?
Transition to breeding season
How long is the estrous cycle in the mare?
21-22 days
What is the normal duration of estrus in the mare?
7 days
What is eversion of the vulva/clitoris a sign of in mares?
Sign of estrus
How long before the end of estrus does ovulation occur and how big is this follicle?
24-48 hours before the end of estrus, follicle about 30-70mm
How does PGF2 alpha reach the ovary to cause luteloysis?
Through systemic circulation
During transition from the breeding to non-breeding season in the mare which of the following is occurring?
A. Melatonin is decreasing in response to decreasing day
length
B. GnRH content is decreasing in response to increasing
melatonin levels
C. GnRH content is decreasing in response to decreasing
melatonin levels
D. GnRH content is decreasing in response to the negative
feedback of estradiol from persistent follicles
B. GnRH content is decreasing in response to increasing
melatonin levels
How is the caprine reproductive cycle affected by melatonin?
Amplitude and frequency of GnRH pulse increases in response to increasing melatonin levels (meaning goats are short day breeders, the more melatonin, the more GnRH which leads to LH surge and ovulation eventually)
What type of estrous cycle do Does (goats) have?
Seasonally polyestrous, short day breeders
What is the luteolytic agent in goats and how is this different from mares?
PGF2 alpha, same thing causing luteolysis but it is delivered via utero-ovarian circulation not systemic circulation
What type of estrous cycles do Ewes (sheep) have?
Seasonally polyestrus (short day)
How many follicular waves are seen in the Ewe’s estrous cycle?
3-4
What is the luteolytic agent in sheep and how is this delivered?
PGF2 alpha, utero-ovarian circulation
During transition from the non-breeding to breeding season
in the ewe which of the following is occurring?
A. Melatonin is decreasing in response to decreasing day
length
B. Melatonin is decreasing the sensitivity of the hypothalamus
to estradiol positive feedback
C. GnRH pulse frequency and amplitude increase in
response to increasing melatonin levels
D. GnRH pulse frequency and amplitude decrease in
response to decreasing melatonin levels
C
What estrous pattern do pigs have?
Non-seasonal polyestrousWh
at is the length of the estrous cycle in pigs?
21 days
When do pigs ovulate?
about 36 hours after the beginning of estrus
What is the most obvious sign of estrus in the pig (the blue one on his slide lol)
Immobile/rigid stance in presence of the boar
When does luteolysis occur in the pig?
Days 13 and 15 after previous estrus
What is the luteolytic agent and how is it delivered in porcine?
PGF2 alpha through utero-ovarian circulation
Which animal is this: seasonally polyestrous, long day breeder
Mare
Which animal is this: Ovulation: 24-48 h before the end of estrus from the ovulation fossa
Mare
Which animal is this: Ovulation: Day 3 (after LH surge), immature oocytes are ovulated
Dog
Which animals experience pseudopregnancy?
Just dog and cat
Which animal is this: polyestrus, induced ovulator, diestrus lasts 60 days in the pregnant animal
Cat
What is the similarity and difference between mares and Does/ewes cycle?
Both are seasonally polyestrous but the mare is a long day breeder and the does/ewes are short day breeders
