1. Canine
Proestrus
Cycle

2. Canine Heat Cycle Typically last on average 21 days
Proestrus and Estrus cycles combined
Usually first cycle starts between 4 to 18 months of age, depending on breed
Smaller breeds start sooner
Larger breeds start later
Most start around 6 months of age
Cycle twice a year, (excluding basenjis who typically cycle once yearly)

4. Proestrus First stage of canine ‘heat’ cycle
Precedes estrus stage
Also referred to as the follicular stage
Ovarian follicles, containing ova (eggs), increase in size, as well as the uterus
Fertilization cannot happen at this stage, due to the absence of a fertile egg being released

5. Proestrus
The hormone estrogen, secreted by the follicles, begins to increase, causing cells of the vaginal walls to cornify, or form into a keratinized horny material.
Estrogen is relatively low at the beginning of proestrus, but peaks towards the end.
In late proestrus, LH hormone will increase, preparing for estrus stage.
Testosterone also increases in late proestrus, which may be responsible for some masculine behaviors in females, such as mounting other dogs.

6. Proestrus Vaginal epithelium proliferates (multiplies).
Diapedesis, (or leakage), of erythrocytes from uterine capillaries.
Increased blood flow (hyperemia).
Serosanguineous discharge (blood and serum).

7. Cytology (Collection)
Sample collected either by swabbing or lavage
A saline moistened swab is inserted vaginally and rotated to exfoliate cells.
Swab is rolled onto a slide, stained, and viewed microscopically.
A dropper with saline is inserted vaginally and squeezed several times to exfoliate cells.
Fluid is collected and placed on a slide in a blood smear manner, stained, and viewed microscopically.

8. Cytology (Cellular) Early proestrus Late proestrus
Mixed population of epithelial cells
Neutrophils present
Erythrocytes present
Late proestrus
Mostly intermediate and superficial epithelial cells
Neutrophils decreased
Erythrocytes increased

9. Erythrocytes, scattered superficial cells, and absence of neutrophils
Early Proestrus
A mixture of nondegenerate neutrophils; parabasal, intermediate, and superficial epithelial cells, erythrocytes, and mucus
Late Proestrus
Erythrocytes, scattered superficial cells, and absence of neutrophils

10. Cytology (Epithelial Cells)
Basal Cells
Youngest vaginal epithelial cells, precursors to more epithelial cells
Round nucleus and small amount of cytoplasm
Parabasal Cells
Smallest cells seen, uniform in size and shape
Round nucleus and basophilic cytoplasm
Intermediate Cells
Vary in size but usually twice the size of parabasal cells
Fairly large amounts of blue-green keratinized cytoplasm
Nucleus size is decreased
Cell is round to irregular and with mildly folded edges
Superficial Cells
Oldest vaginal epithelial cells
Either have a small, round, degenerative (pyknotic) nuclei or lacking one completely
Largest amounts of blue-green keratinized cytoplasm
Cell is cornified, angular and with folded edges

11. Serum concentrations of estrogen rise during proestrus, leading to capillary breakage and leakage of red blood cells through uterine epithelium, as well as proliferation of the vaginal epithelium.
Examination of vaginal smears from early to late proestrus will reveal a gradual shift from intermediate and parabasal cells to superficial cells. Typically, red blood cells are present in large numbers and neutrophils are commonly observed. Large numbers of bacteria are also often present.

12. Signs of Proestrus Lasts 9 days (Average 3-17 days)
Vulvar tip swells, becomes soft and pliable
Small amounts of bloody vaginal discharge
Likely to see an increase in urination
Possible appetite changes
Attraction of nearby males

13. Behavioral Changes
Changes can range from becoming more affectionate towards owner or to being more standoffish and grumpy
Appetite may also be affected, from mild disinterest to rummaging for scraps
Like in humans, individual responses to these changes will vary from dog to dog

14. Receptiveness to Males
Males are attracted to females.
Females are not yet receptive
Will most likely not yet ‘stand’ for male
Tail-tucking: bitches may ‘guard’ vulva or even sit down when male dogs approach

15. (The End!) Tashema Samantha Kirk McDevitt Miranda Allison Pestinger
Rodricka
Becnel
Samantha
McDevitt
Allison
Frazier
Alisha
Pierce
Oct.2nd.08