1. Estrous Cycle of the Bitch

Question 1

do bitches ovulate mature eggs? how long do eggs take to become mature? does the oocyte need to be mature to be fertilized?

Answer 1

Do not ovulate mature eggs
◦ Takes 48 hours on average to become mature
◦ Canine oocytes have longer lifespan > extends the breeding period but fertilization can only occur once the oocytes are mature.

Question 2

what hormone level rises before ovulation?

Answer 2

Progesterone levels begin to rise prior to ovulation
◦ Use progesterone to determine when ovulation occurs
◦ Hormones are the same pregnant or not

Question 3

The stages of the canine estrous cycle

Answer 3

proestrus, estrus, diestrus, anestrus

Question 4

are canines poly or mono estrus?

Answer 4

monoestrus, non seasonal

Question 5

proestrus+ estrus =

Answer 5

heat

Question 6

when is bitch puberty?

Answer 6

When the first proestrus occurs
Occurs earlier in small breeds vs. large breeds
◦ Average 8-14 months (range 6 – 26 months)

Question 7

should we breed on first heat?

Answer 7

no

Question 8

how is the first heat likely to differ from subsequent heats?

Answer 8

Likely to be “irregular” compared to other cycles ◦ Split or silent heats common

Question 9

what is a split heat?

Answer 9

Split heat = heat starts then stops without ovulation. Starts again later.

Question 10

what is a silent heat?

Answer 10

Silent heat = very little vaginal discharge.

Question 11

4 strategies we can use to determine the stage of estrus

Answer 11

Vaginoscopy
Vaginal cytology
Progesterone levels
Behavior/receptivity

Question 12

average length of proestrus?

Answer 12

Average length = 9 days (0-27 day range)

Question 13

what day of heat do we see the first drop of blood?

Answer 13

day 1

Question 14

what hormone level rises during proestrus? how does this effect the vagina and vulva?

Answer 14

Estrogen levels are rising
◦ Edema of vaginal epithelium; edema of the vulva

Question 15

external cues of proestrus?

Answer 15

◦ Swollen vulva
◦ Serosanguineous vaginal discharge
◦ May start “flagging”

Question 16

behavioural changes during proestrus?

Answer 16

Males are interested in the bitch
*Bitches are typically not receptive yet
*Bitches may mount other bitches
*Bitches in heat may become aggressive towards other bitches

Question 17

vaginal epithelium changes during proestrus?

Answer 17

Vaginal epithelium > goes from 5-10 cell layers to 10-20 cell layers
Cytology of vaginal swab
*Parabasal cells, intermediate cells

Question 18

average length of estrus

Answer 18

Average length = 9 days (4-24 day range)

Question 19

hormone changes during estrus

Answer 19

Stage at which LH surge occurs, ovulation occurs and fertile period occurs = when breeding occurs “standing heat”

Estrogen levels elevated initially; peak; starts decreasing at LH

Progesterone levels start to rise at LH, continue to elevate at ovulation & remain elevated

Question 20

how can we estimate the LH surge?

Answer 20

We can use progesterone to estimate the LH surge
◦ Coincides with the initial progesterone rise

Or can use in house LH test (Witness® LH)
◦ Usually reserved for important breedings; frozen semen breedings
◦ Can get costly, time consuming
◦ More accurate

Question 21

how does LH surge timeline relate to ovulation?

Answer 21

LH surge occurs 48 hours before ovulation

Question 22

how do we measure progesterone?

Answer 22

Ran on SERUM (ideally separated 20-30 mins after blood draw)
Place in red top tube
◦ No serum separator tubes

Question 23

vulva and vagina changes during estrus

Answer 23

Vulva becomes less turgid as estrogen decreases, serosanguineous discharge can diminish, can become lighter
Edema of vaginal epithelium decreases = crenulation

Question 24

what behaviours will the female engage in during her fertile period?

Answer 24

Female should be receptive to male during fertile period ◦ Flagging
◦ Seeks out the male

Question 25

vaginal epithelium characteristics during estrus?

Answer 25

Vaginal epithelium > 20-30 cell layers at estrogen level peak
Cytology of vaginal swab
◦ Cornified epithelial cells

Question 26

length of diestrus?

Answer 26

Length = average 2 months (range 56-58 days if pregnant; if not pregnant 56-90 days)
◦ If pregnantà62-64 days from ovulation (canine gestation = 63 days +/- 1 day)

Question 27

is bitch receptive to breeding during diestrus?

Answer 27

Bitch is no longer in “heat”
◦ No longer receptive to breeding

Question 28

when does diestrus occur relative to ovulation?

Answer 28

Occurs 6 days after ovulation (or 8 days from the LH surge)

Question 29

vulva and vagina changes during diestrus?

Answer 29

Vulva diminishes in size, vaginal discharge subsides, vaginal epithelium flattens

Question 30

hormone profile during diestrus?

Answer 30

Period of time when progesterone is high; estrogen is low

Question 31

vaginal epithelium characteristics during diestrus?

Answer 31

Vaginal epithelium peels off > goes back to 5-10 cell layers > 2-4 cell layers

Cytology of vaginal swab
◦ Parabasal cells
◦ Intermediate cells
◦ Neutrophils

Question 32

length of anestrus?

Answer 32

Length = average 4 months (range 4-12 months)

Question 33

what hormone drops during anestrus?

Answer 33

Progesterone drops

Question 34

what is anestrus? what is it important for? vaginal and vulvar character?

Answer 34

Period of reproductive quiescence Important stage for uterine involution
◦ Uterine involution is a necessary process Bitches are not receptive to breeding
Vulva small, no vaginal discharge

Question 35

Reproductive Consultation - why is it important?

Answer 35

◦ Our responsibility to educate clients on responsible breeding
◦> Time commitment
◦> $$$
◦ Should only be breeding mature, healthy, good dogs
◦> Clearances
◦>Representative of the breed

Question 36

Bitch breeding management considerations

Answer 36

History
◦ Medical
◦ Reproductive (Brucella canis status)

Physical exam

Reproductive exam
◦ Digital palpation
◦ Vaginal swab for cytology ◦ Vaginoscopy

Serum progesterone levels
◦ Usually blood taken every 2 days

Question 37

Breeding methods

Answer 37

Natural

Vaginal artificial insemination (AI)
◦ Plastic pipette ($)
◦ MAVIC catheter ($$)

Transcervical insemination (TCAI)
◦ $$$
◦ Semen is directly deposited in uterus ◦ Can usually do without any sedation

Surgical insemination (SAI)
◦ $$$$
◦ Semen is directly deposited in the uterus
◦ More invasive than TCAI – surgery under general
anesthesia

Pregnancy rates equivalent for TCAI as they are for SAI

Question 38

Types of semen

Answer 38

Fresh
◦ Can breed with standard vaginal AI, MAVIC catheter or TCAI

Fresh chilled
◦ Semen collected, evaluated (hopefully), processed elsewhere & shipped
◦ Is stored cool, not frozen
◦ Increased timing is required > need to give stud dog owner 24-48hrs notice
◦ Should be shipped 24hr priority > allows for semen from the US or in other parts of Canada to be used
◦ Standard vaginal AI, MAVIC or TCAI

Frozen
◦ TCAI or SAI only
◦ More in depth timing is required (confirm ovulation date with LH witness test)
◦ Progesterone timing every 2 days
◦ Stored in liquid nitrogen
◦ Can be shipped internationally (Europe, Australia, etc.).

Question 39

Take home points: estrogen levels during heat and effect, pogesterone surge timiing, LH surge timing, fertile period. More processed semen means what?

Answer 39

Estrogen is elevated in heat
◦ Edema of vulva
◦ Edematous vaginal epithelium
◦ Cornification on cytology

Progesterone rises prior to ovulation
◦ Use progesterone to determine ovulation date
◦ Rise typically coincides with LH surge

LH surge occurs 48 hours prior to ovulation Dogs ovulate immature eggs
◦ Fertile period = 2-4 days post ovulation

The more ”processed” the semen is = more precise timing required