Canine Estrous Cycle, Vaginal Cytology, Breeding Mgmt Flashcards
Puberty in dogs occurs ______
6-24 months (average age of 7-10 months)
- small dogs reach puberty earlier than big dogs
Canine seasonality
Non-seasonal monoestrus
What are the 4 stages of the estrous cycle?
- protestrus
- estrus
- diestrus
- anestrus
What are the sources of reproductive hormones?
- estrogen: preovulatory follicle
- progesterone: CL and some from adrenal
- LH: pituitary
- FSH: pituitary
- GnRH: hypothalamus
GnRH
Causes release of FSH and LH
FSH
Stimulates preovulatory follicles
LH
Causes ovulation
Estrogen
initiates proestrus
Progesterone
Maintains pregnancy
- there is no placental takeover of progesterone in dogs!!
Behavioral changes
- attractiveness
- acceptance: when the female will stand for mating
- posture: rigid stance, deflects tail to one side, elevate vulva
Physical changes
- color: pale (anestrus) to pink
- swelling: due to estrogen, causes Na retention in vulvar tissues
- discharge: serosanginous, blood comes from the wall of the uterus (diapedesis)
Vaginal cytology
Percentage of cornification
- epithelial cells will cornify in response to high levels of estrogen –> are further from the blood supply due to swelling
Endocrine level
Identify LH surge directly or indirectly
- most accurate staging method
Proestrus
Bitch is attractive but not receptive
- vulva begins to swell and discharge starts
- vaginal cytology: intermediates, some cornified, RBCs
- basal progesterone, rising estrogen
- duration: 6-11 days (avg 9 days)!!!!
Estrus
Bitch is attractive and receptive
- vulva is less turgid, straw colored discharged
- vaginal cytology: all cells are cornified (80-90%)
- progesterone rises from preovulatory lutenization, estrogen has peaked and is falling, LH surge
- duration: 3-20 days (avg 5-9 day)!!
Diestrus
Bitch will no longer accept male
- vulva reduces in size and discharge stops
- vaginal cytology: intermediate, parabasal cells, lots of WBCs
- CL produces large amounts of progesterone
- duration: 57 days if pregnant, 60-100 days if not pregnant
Anestrus
Period of sexual quiescence
- uterus is involuting and preparing for next cycle
- behavior similar to spayed female
- vaginal cytology: parabasal and intermediate
- progesterone and estrogen are both low
- duration: 2-9 months
Proestrus averages ______
9 days
Estrus averages _____
9 days
LH surge triggers ovulation in ______
48 hours
- need to identify LH surge to determine when ovulation occurs
Bitch ovulates primary oocytes over a period of _____
36 hours
- staggered release
Each oocyte undergoes final phase of meiosis that takes ______
48 hours
Eggs are fertilized in oviducts ______ after LH surge
4-5 days
Fertilized eggs remain in oviduct for ______
8-10 days
Embryos migrate to uterus by day ____
15
- implantation occurs
______ supports pregnancy throughout gestation
CL!
If you want to prevent implantation right after an accidental breeding, than give ______
Estrogen!
- prevents embryo from reaching the uterus by tightening the utero-tubular junction
Breeding management
- behavior of female
- vaginal cytology
- endocrine testing
Vaginal cytology
Used to determine presence of estrogen
- estrogen’s effect on vaginal epithelium
- cornified cells –> estrogen levels are or recently were elevated
- parabasal cells: estrogen levels are low
Vaginal cytology technique
- swab cranial vagina
- roll on slide
- stain with Diff-Quik
What are limitations of vaginal cytology?
Used only to stage the estrous cycle
Proestrus on cytology
Mixture of epithelial cells, some parabasal some intermediate
- few superficial cells seen early, many seen late
- RBCs seen throughout
- percentage of cornified cells increases as proestrus progresses
Estrus on cytology
Majority are cornified cells (90%), many anuclear
- can see large numbers of bacteria
- few RBCs or WBCs
Diestrus on cytology
Abrupt return to parabasal and intermediate cells (occurs over 24 hours)
- lots of WBCs
- can see metestrum cells and foam cells
Accuracy of timing depends on ______
Breeding situation
- fresh semen can live in repro tract for 1 week
- frozen semen will only live 12-18 hours
Basics for the average bitch where live cover breeding will be supervised by the owner
Breed on 1st day of standing heat and every 2-3 days thereafter until bitch refuses mating
If you are determining the fertile period, then breed _____
3-6 days after LH peak (1 day after ovulation)
Progesterone testing
Progesterone levels will coincide with LH surge
- RIA or in-house kit
- should test every 2-3 days until ovulation is confirmed
LH testing
Identify LH surge in serum sample
- sendout or in-house kit (only gives positive/negative result)
- must test often due to short duration of surge (18-24 hours)
Progesterone values
- P4 rising through 2.0 coincides with LH surge
- P4 between 4-6 coincides with ovulation
- P4 greater than 10 coincides with fertile period
- always assure animal has ovulated prior to breeding!
LH surge –> ovulation –> fertile period
Dogs will whelp ____
64-65 days from LH surge
- if you look at diestrus cytology, will whelp 57 days later
