Canine Proestrus Cycle

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)

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

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.

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

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.

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

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

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

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.

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

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

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

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