Canine Estrous Cycle & Breeding Management

Question 1

What structure is present in the cranial vagina (before you get to the cervix) of the bitch that serves as an obstacle to insemination?

Answer 1

dorsal median vaginal fold

Question 2

Occurrence of puberty is based on the ability of the hypothalamic neurons to produce sufficient ________

Answer 2

GnRH​

Question 3

T/F: Occurrence of puberty is typically ~6 to 10 months in all canine breeds

Answer 3

False

• 6-10 months in smaller breeds
• ~2 years for some larger breeds
• Variable in some breeds (English Setter 7-20 months)

Question 4

T/F: Progesterone starts to climb at the beginning of proestrus in the bitch

Answer 4

False

Progesterone starts to climb at the beginning of estrus in the bitch

Question 5

LH peak occurs between what two stages of the estrous cycle in the bitch?

Answer 5

proestrus and estrus

Ovulation occurs a few days later and fertilization occurs a few days after that

Question 6

What is the average duration for proestrus and estrus in the bitch?

Answer 6

7-9 days each (14-18 days total)

However, each bitch is unique

Question 7

What is the average duration of anestrus in the bitch?

Answer 7

90-150 days

(3-5 months)

Question 8

The time from the beginning of one estrus to the beginning of the next estrus is termed:

Answer 8

interestrus period

Average duration is 7 months. Larger dogs tend to have shorter interestrus periods

Question 9

T/F: Cornification of vaginal cells can be used to accurately predict time of receptivity, LH surge, and ovulation

Answer 9

False

Cornification of vaginal cells can not be used to accurately predict time of receptivity, LH surge, and ovulation. Period of maximum cornification varies between bitches

Question 10

You introduce a cotton-tip swab into the caudal vagina of the bitch for vaginal cytology. You note blood on the swab. What stage of the estrous cycle is the bitch in?

Answer 10

Proestrus

Question 11

What hormone predominates during proestrus?

Answer 11

Estrogen

Question 12

This vaginal cytology is consistent with what stage of the estrous cycle in the bitch?

Answer 12

Proestrus

• Cornified epithelial cells increasing - “corn flakes” - large angular cells with small/no nuclei
• Red blood cells
• White blood cells - PMN’s - variable in number - decreasing in amount over time
• Debris in the background

Question 13

Vaginal cytology of the bitch yielding greater than 90% superficial epithelial cells would be indiciative of:

Answer 13

estrus

• >90% Cornified superficial epithelial cells (squames), lots of anuclear squames
• One rule of thumb - 100% Cornified and 50% Anuclear
• No WBC’s – vaginal wall too thick to cross
• Few RBC’s
• Little or no debris in background of slide
• Sometimes see bacteria
• Cells may clump (“sheeting”) just prior to cytologic diestrus

Question 14

During estrus in the bitch, the first sharp rise of progesterone is correlated with a peak in ________

Answer 14

LH

• Progesterone starts to rise during estrus. The initial rise coincides with the LH peak.
• Preovulatory rise is due to follicular estrual luteinization
• P4 starts to rise, when estrus ends, the P4 is already greatly elevated over baseline

Question 15

The period in the estrous cycle of the bitch that is marked by a sharp decrease (50%) in the percentage of superficial cells and an increase in small intermediate and parabasal cells is:

Answer 15

diestrus

The female begins to refuse the male, although she may still be attractive to males. The uterus develops remarkable tone. Duration of diestrus is variable, but generally is 60 days (range of 45-90)

Question 16

Maximum crenulation occurs during what stage of the estrous cycle in the bitch?

Answer 16

Estrus

Vaginal mucosal folds become progressively wrinkled (crenulated) in conjunction with ovulation and oocyte maturation.​

Question 17

In the bitch, a ________ oocyte is ovulated

Answer 17

primary

• In the bitch, a primary oocyte (2N) is ovulated​ (Prophase 1) and must go through further meiotic division to a secondary oocyte (1N) before the oocyte is ready for fertilization​. This takes 2-3 days.*
• The secondary oocyte is then viable for 3-4 days (in general) and then become atretic if not fertilized*

Question 19

Assessment of ________ is now the modern standard for assessing ovulation; assessing when to breed bitches

Answer 19

progesterone

• Principle:
  
  • 2 ng/ml = LH peak
  • 5 ng/ml = Ovulation starting
  • Confirm ovulation (>15 ng/ml)
  • Ovulation - rise in P4 of 3 ng/ml in 24 h

Question 20

Ovulation can be confirmed in the bitch by seeing a rise in P4 of ______ ng/mL in ______ hours

Answer 20

Ovulation can be confirmed in the bitch by seeing a rise in P4 of 3 ng/mL in 24 hours

Question 21

Bitches should be bred _____ and _____ hours after P₄ = 5ng (ovulation) for natural or shipped semen

Answer 21

Bitches should be bred 48 and 96 hours after P₄ = 5ng (ovulation) for natural or shipped semen

(alternatively 24 and 72 h)​

Question 22

Bitches should be bred _____ hours after P₄ = 5ng (ovulation) or higher for frozen semen

Answer 22

Bitches should be bred 72 hours after P₄ = 5ng (ovulation) or higher for frozen semen

(Breed at 96 h with TCI and second dose of frozen semen)​

Question 23

T/F: Higher conception rates and larger litter sizes are observed with natural breeding than with artificial insemination in the bitch

Answer 23

True

Question 24

LH assays are available as an in-house kit and are helpful in breeding management. Bitches should be bred _____ days after the LH peak

Answer 24

4-6 days

Question 25

Canine oocytes are good for up to _____ hours post-ovulation

Answer 25

108 hours

• Canine oocytes are good for up to 108 hours post-ovulation
  
  • Could breed sometimes into diestrus with good results if you by-pass the closed cervix (ie surgical insemination or trans-cervical)

Question 27

What structure in the dog’s external genitalia forms the “lock” during copulation?

Answer 27

**bulbus glandis**

Question 29

When performing AI in a bitch with fresh semen, what is the minimum suggested breeding dose? * 100 million motile sperm * 200 million motile sperm * 300 million motile sperm * 500 million motile sperm * 1 billion motile sperm

Answer 29

**200 million motile sperm**

Question 30

Normal motility and morphology of spermatozoa in a normal stud dog should be greater than what, respectively? * 50%, 80% * 60%, 60% * 80%, 80% * 80%, 60% * 50%, 50%

Answer 30

**80%, 80%**

Question 32

When two males breed the same female during a single estrus, this is termed:

Answer 32

**superfecundation** *In Greek mythology, Heracles (Hercules) and his twin Iphicles are examples of heteropaternal superfecundation, with Heracles fathered by the god Zeus and Iphicles by a mortal man Amphitryon*

Question 33

Which of the following are used in chemical ejaculation of the dog? * Oxytocin * PGF_2A * hCG * A and B only * All of the above

Answer 33

**A and B only** * *Oxytocin* * *5 IU subcuticular or intramuscular 5-10 minutes prior to manual stimulation* * *Prostaglandin F_2α* * *0.1 mg/kg subcuticular or intramuscular 15 minutes prior to manual stimulation* *The myofibril cells of the epididymal duct are smooth muscle cells- may respond to oxytocin and PGF2a*

Question 34

Which artificial insemination technique requires surgical intrauterine deposition of semen? * Natural Service * Fresh semen * Fresh chilled * Chilled Extended * Cryopreserved

Answer 34

**Cryopreserved​** *Surgery: midline laparotomy, small volume, 22 g needle (or catheter), place obliquely into lumen, visualize distention of uterine horn with injection to insure you are in lumen*

Question 35

When using cryopreserved semen to AI the bitch, she should be inseminated when (in relation to the LH surge)? * 2 days prior * On day of LH surge * 1-2 days post LH surge * 2-4 days post LH surge * 5-6 days post LH surge

Answer 35

**5-6 days post LH surge**

Question 36

What hormone in the bitch is measured as an indirect assay for LH?

Answer 36

**progesterone**