Assisted reproduction in dogs Flashcards
At what age do bitches start cycling?
varies with breed and size
6m to even 24 months
The first heat in a bitch is frequently
a silent heat.
What is a split heat?
a heat that begins but then stops and then starts again
usually in a bitch as they’re still maturing e.g. the first heat can be split
Should we breed an animal on first heat?
No. The risk of dystocia is higher!
Is fertility lower in the first heat?
No. Fertility is normal, even if it’s a “split heat!”
Stages of the dog heat cycle and their length.
diestrus, 60 days
anestrus, 90-150 days
proestrus, approx. 9 days
estrus, approx. 9 days
vaginal cytology swab collection from where?
cranial/anterior portion of the vagina
very important to soak the swab in saline before taking swab so as not to injure the mucosa (can cause bleeding if you use a dry swab)
Vaginal mucosa epithelial cell types/characterization.
non-cornified: parabasal and intermediate
cornified: superficial and anucleate
identify cell type and stage of cycle
parabasal, non-cornified epithelial cells of the vagina
indicate proestrus
During proestrus, the levels of estrogen rise, causing the vaginal epithelial cells to transition from parabasal to cornified. As the cycle progresses, cornified epithelial cells become predominant, indicating the onset of estrus.
identify cell type and stage of cycle
intermediate, non-cornified epithelial cells of the vagina. neutrophils may also be a normal finding at this stage.
indicate later stage proestrus or early estrus before cornification.
identify cell type and stage of cycle
superficial, cornified epithelial cells of the vagina. nucleus may be pyknotic. these indicate estrus peak late stage estrus
more than 90% of the cells should be cornified to signify estrus.
anucleation (loss of nucleus) is NOT a good indicator for estrus because pyknosis does not occur in all bitches’ vaginal cytology.
identify cell type and stage of cycle
anucleate, cornified epithelial cells of the vagina. RBCs are typical in diestrus as are neutrophils but neutrophils shouldn’t be too abundant during estrus because they impede successful conception.
indicates late stage estrus and diestrus
Anucleate, cornified epithelial cells are a result of further maturation and keratinization of the vaginal epithelial cells.
In bitches, the luteal phase can also be referred to as?
diestrus, lasts approx. 60 days
What is flagging in bitches?
When the dog is in heat and receptive to breeding, it will move its tail to the side upon stimulation/touch of the perineal area.
When does progesterone begin to rise in dogs?
Progesterone begins to rise BEFORE ovulation in dogs. Just shortly before the LH surge, P4 begins a steady increase.
Pre-ovulatory elevation of Progesterone (1.9-2.9 ng/ml)
Ovulation > 5 ng/ml
At the end of the Estrus P4 is already quite high.
the bitch Oocyte degenerates how many days after maturation?
degenerates 3-4 days after maturation.
Bitch ovulation occur how long after LH peak?
24-48 hours post LH peak
Multiple ovulations can occur over the course of 24 hours as multiple oocytes will have slightly different maturation/are not 100% synchronized.
What causes the end of Diestrus in the bitch?
diestrus lasts about 60 days so the same length as a pregnancy.
it is not actually known exactly what induces the end of diestrus/induces luteolysis in dogs.
in cows its PG-F2alfa from the endometrium.
When estrogen rises during proestrus, the vaginal epithelium becomes
hyperplastic and more cornified.
During proestrus the percentage of cornified cells increases by about 10%/day until you see about 100% cornification during estrus.
You may also see RBCs during proestrus.
describe vaginal epithelial cell cornification on the 1st day of diestrus?
drops from over 90% cornification very suddenly to 50% or lower. this signifies the first day of diestrus.
dark blue line in image
cornification rate/percentage in the middle of proestrus?
50% cornification
increases at a rate of 10% per day
once its over 90%, you officially have estrus
Non-cornified vaginal epithelial cell
Parabasal cells have a large stippled nucleus and a rounded cytoplasm The nucleus is large compared to the cytoplasm.
Intermediate vaginal epithelial cells have a have a stippled nucleus and more cytoplasm than parabasal cells (so the nucleus is smaller). The cytoplasm may even become angular (as opposed to a more round sunny side up egg looking cell).
Cornified vaginal epithelial cell
Superficial cells have a pyknotic nucleus and angular cytoplasm. There is no stipling in the nucleus.
Anuclear vaginal epithelial cells have no visible nucleus and angular cytoplasm.
On the first day of diestrus the cells in the swab abruptly change to
around 50% non-cornified.
This day that the smear changes from 100% cornified cells to 50% non-cornified cells is denoted as the first day of cytologic diestrus.
You may see an influx of Polymorphonuclear leukocytes at this time to help clean up all the cellular debris.
How long before 1st day of diestrus is ovulation?
6 days prior to the first day of diestrus is the most likely time for the dog to have ovulated. obviously there can be variations but this is one rule of thumb.
(so ovulation is 4th day of estrus commonly, see default cycle scheme)
Hormonal assay to assess bitch cycle?
Hormonal assay: LH or Progesterone
LH would need to be measured more frequently than P4
95% conception rate when insemination or breeding between estrus day 2 - day 8
(ovulation commonly on estrus day 4 but fresh semen should be viable for at least 2 days in the repro. tract)
50% cornified cells / 50% non-cornified cells
indicates 1st day of diestrus. RBCs not unusual
there’s a neutrophil (not conducive to conception) and more than 50% (maybe up to 70%) cornified cells.
this is mid-late proestrus
beginning of estrus
> 80% cornified cells, more bacteria visible which are normally increased in estrus vaginal cytology. P4 very low, below basal.
> 90% cornified epithelial cells
estrus.
nuclei less clear, pyknosis?
cornification percentage high
estrus
progesterone indicates ovulation has occurred
breeding or insemination can be performed the next day and again in 2-3 days, depends on if semen is fresh or chilled.
what’s this
artificial insemination catheter for bitches
diestrus, maybe 2nd day of it as slightly more than 50% of the cells are no longer cornified.
RBCs present
>90% epithelial cell cornification
estrus
do progesterone to narrow it down further (beginning or end of estrus)
diestrus
cornification percentage has dropped to below 50%. neutrophils are common as they come to clear out debris after estrus.
