Canine Breeding Management

Question 1

What is the Canine Estrus cycle like?

Answer 1

• Non-seasonal, monoestrus breeders
• Puberty: 6-23 months
  
  • average 10-14
• Interestrus interval 4-13 months
  
  • Average 7 months
  • German shepherd & Rottweiler 4-5mo
  • Basenji and Mexican Hairless 12 mo

Question 2

What are the different classifications of vaginal epithelial cells?

Answer 2

• Parabasal cells
• Intermediate cells
• Superficial/Cornified cells

Question 3

What are parabasal cells?

Answer 3

• Smallest epithelial cells
• Round or nearly round
• High nuclear to cytoplasmic ratio
• Prevalent during diestrus and anestrus
  
  • Early proestrus
  • Absent during estrus

Question 4

What are vaginal intermediate cells

Answer 4

• Vary in size and shape
• Diameter 2-3x that of parabasal cells
• Small intermediates
  
  • nearly round or oval with large, prominent nuclei
• Large intermediates
  
  • polygonal with small nuclear to cytoplasmic ratio
• Prevalent during all stages of the cycle except for estrus

Question 5

What are vaginal superficial/cornified cells?

Answer 5

• Largest cells
• Polygonal in shape and flat
• May have appearance of being rolled up
• Absent or pyknotic nuclei
  
  • fully cornified - absent nuclei
• Often seen in large sheets of fully cornified cells
• Increase in prevalence during proestrus
  
  • About 10% daily
• Large numbers indicate estrus (>90%)
• Abrupt decline marks onset of diestrus (<50%)
• Normally not seen during anestrus

Question 6

What other cells are seen on vaginal cytology

Answer 6

• Erythrocytes
  
  • observed in large numbers during proestrus
  • Rarely seen through estrus and early diestrus
• Neutrophils
  
  • common during diestrus
  • rare during estrus
• Bacteria - often seen in large numbers

Question 7

What happens during Proestrus in the bitch? length? behavior? physical?

Answer 7

• Duration 3-17 days (average of 9)
  
  • Follicular development results in gradual increase in estrogen concentrations
  • Rise in estrogen leads to vaginal epithelial hyperplasia
  • Estrogen Peaks 2-3 days before ovulation then rapidly declines during estrus
• Behavior:
  
  • attraction of male dog to female
  • Female will not allow mating
• Physical Changes:
  
  • swollen vulva and vagina
  • Serosanguinous vulvar discharge form the uterus
• Vaginoscopy - difficult to visualize vaginal lumen

Question 8

What does vaginal cytology look like during proestrus?

Answer 8

• Early Proestrus (low estrogen)
  
  • Parabasal epithelial cells
  • Intermediate epithelial cells
  • RBCs and Neutrophils
• Mid - late proestrus (estrogen increases)
  
  • Superficial “cornified” epithelial cells
  • >90% cornified by the end of proestrus
  • Fewer neutrophils

Question 9

What does the vaginal cytology look like during Estrus?

Answer 9

• >90% cornified superficial epithelial
• no neutrophils
• +/- RBCs

Question 10

What happens during Diestrus in the bitch? length? behavior? physical?

Answer 10

• Duration 50-80 days (60 average)
  
  • Progsterone elevated throughout diestrus
    
    • CL source
  • Diestrus ends with decline in progesterone
• Behavior - no longer receptive to male
• Physical Changes:
  
  • Vulva no longer swollen or flaccid
  • No vulvar discharge
• Vaginoscopy - pale mucosa

Question 11

What does the vaginal cytology look like during diestrus in the bitch

Answer 11

• Sharp decline in cornified epithelial cells on D1 of diestrus
  
  • 40-60% parabasal and intermediate cells
  • ~3 days before end of behavioral estrus
  • ~2-5 days after oocyte maturation
  • ~5-7 days after ovulation
  • ~8-9 days after LH surge

Question 12

What happens during Anestrus in the bitch? length? behavior? physical?

Answer 12

• Duration: 2-9 months
  
  • Progesterone decreases just before parturition or gradually after CL regression in the non-pregnant female
  • Progesterone < 1-2 ng/ml
• Behavior - not receptive to male
• Physical changes:
  
  • Period of uterine involution
    
    • 70 days for non-pregnant female
    • 90 days for postpartum female

Question 13

What does the vaginal cytology look like during Anestrus in the bitch

Answer 13

• Parabasal epithelial cells
• No RBCs
• +/- neutrophils
  
  • low number if present

Question 14

When is Luteinizing hormone present in the Estous cycle? significance?

Answer 14

• LH peak: Day 0 of estrous cycle
  
  • occurs in response to decline in estrogen levels and rise in progesterone levels
  • Marks the end of the follicular phase of the estrous cycle
    
    • triggers ovulation
  • Marked increase over usual baseline levels develops over 24-48 hr period
  • Return to baseline
• Daily measurement to ID exact day of pre-ovulatory LH peak
  
  • LH >1ng/ml

Question 15

When is Progesterone hormone present in the Estous cycle? significance?

Answer 15

• Anestrus: <1ng/ml
• Proestrus: remains low until rising 1-2 days prior to LH surge
  
  • 2-3 ng/ml at LH peak
• Estrus: 5-8 ng/ml at ovulation, 7-20 during fertile period
• Diestrus: steadily rise to peak of 15-80 ng/ml

Question 16

What happens before and during Ovulation?

Answer 16

• Estrogen Peaks 1-3 days before LH surge
• Primary oocytes ovulate 2 days after LH surge
• Oocyte maturation requires 2 days after ovulation and before fertilization can occur
• Lifespan of mature oocyte is 2-3 days
• Ovulation occurs 6 days prior to D1
  
  • Determine if mating was during fertile period
  • Determine whelping dates: 57 +/- 1 days

Question 17

Summarize the cyclic changes that occur during Estrous:

• Duration
• Vaginal cytology
• Vulva appearance
• Discharge
• Behavior
• Estrogen (pg/ml)
• Progesterone (ng/ml)
• LH (ng/ml)

Answer 17

Question 18

Why would mating be unsuccessful?

Answer 18

• Inappropriate timing
• Dominant female
• Inexperienced male
• Vaginal abnormalities
• Pain (spinal, rearlimb, prostatic)

Question 19

When should AI be used in canines?

Answer 19

• Indications:
  
  • inability to copulate normally
  • Subfertile male
  • Divide ejaculate between several females

Question 20

When should bitches be artificially inseminated with Cooled semen? How is the optimum timing detected?

Answer 20

• Vaginal cytology: Every 48 hrs during proestrus
  
  • Once vaginal epithelial cells >50% cornified start measuring progesterone
• Serum Progesterone: every 24-38 hrs until ovulation is confirmed
  
  • 2-3 ng/ml coincides with LH peak
  • 5-8 ng/ml coincides with ovulation
• LH may be measured every 24 hrs to ID LH peak (>1ng/ml)
• Once LH surge has occurred, breed 3-7 days later
  
  • one insemination: breed on day 5-6
  • Two insemination: breed on days 3 and 5 or 4 and 6
• Ideal to inseminate w/in 24-48 hrs of colllection and extension
  
  • Extended semen: viable p to 48 hrs (some up to 96h)
• Minimum insemination dose: 200x10⁶ motile sperm

Question 21

When should bitches be artificially inseminated with Fresh Semen?

Answer 21

• Vaginal cytology every 48 hrs during proestrus
• Inseminate every 48 hrs starting once vaginal cornification > 90%
  
  • discontinue once cytologic diestrus is observed
• Deposit fresh, raw semen in the cranial vagina at the external cervical os
  
  • minimum insemination dose 200x10⁶ motile sperm
• May extend 1:1 with extender for added volume

Question 22

When should bitches be artificially inseminated with Frozen Semen?

Answer 22

• Inseminate on day 3 or 4
• Intrauterine deposition of semen
  
  • Post thaw semen has poor motility
• Minimum insemination dose 100-300x10⁶ motile sperm

Question 23

What is False pregnancy in bitches?

Answer 23

• All normal, nonpregnant females experience false pregnancy after estrus
  
  • not all will exhibit clinical signs
• Diestrus, or luteal phase, physiologically and hormonally cannot be differentiated form pregnancy
• Results from physiologic decline in progesterone ate the end of diestrus
• Lasts approximately 4-6 weeks
• Characterized by:
  
  • mammary development
  • Lactation
  • abdominal enlargement and slight uterine enlargement
  • Behavior of whelping and mothering

Question 24

How is false pregnancy in bitches diagnosed?

Answer 24

• Clinical signs
• No pups seen on radiographs or ultrasound
• Undetectable serum relaxin conentration

Question 25

What is the treatment for false pregnancy in bitches?

Answer 25

• Not necessary in mild cases - self limiting
• Avoid physical stimulation of the mammae
• Remove any objects that female has adopted
• Spaying after remission of clinical signs will prevent recurrence
• Megestrol acetate: 2.5 mg/kg/day orally for 8 days
  
  • only approved treatment
  • may relapse after treatment
  • Progestogen that suppresses signs of false pregnancy initiated by progesterone withdrawal at the end of diestrus
  • long term or repeated therapy may predispose female to pyometra or cystic endometrial hyperplasia
• Alternative non-approved treatments:
  
  • Mibolerone: 0.6-37 ug/kg/day for 2-10 days (16 ug/kg/day for 5 days)
    
    • weak, synthetic androgen
    • Side effects: clitoral hypertrophy, vaginal discharge, mounting behavior, musky odor
    • If given to pregnant females, birth defects may develop in utero
    • Off-label for treatment of false pregnancy
  • Bromocriptine 30 ug/kg/day orally for 16 days
    
    • dopamine agonists ⇢ inhibits prolactin