Canine and Feline Reproductive Physiology

Puberty

1. Period where the capability of reproduction is attained = activation of the hypothalamic pituitary-gonadal axis

2. Different criteria (first proestrus, first ovulation, capability of sustaining a pregnancy)

3. Maximum reproductive capability is not achieved until 3rd or 4th estrus (higher odds for dystocia)

First proestrus, first ovulation, capability of sustaining a pregnancy

Criteria of puberty

Breed, gender, weight, environmental exposure, social cues

Factors affecting puberty in dogs

Split/false heat (no ovulation), silent heat, too young for breed testing, higher risk for dystocia

Risks with breeding young dogs

Breed, environment, season

Factors affecting puberty in cats

Dogs

Dogs or cats?:

1. Not seasonal

2. Monoestrous

3. Polytocous (multiple offspring in same litter)

4. Spontaneous ovulation

Cats

Dogs or cats?:

1. Seasonal (long-day breeder)

2. Polyestrous

3. Polytocous (multiple offspring in same litter)

4. Induced ovulation

Proestrus (9 days), estrus (9 days), diestrus (60 days), anestrus (80-240 days)

Phases of estrous cycle in the dog and average lengths of each phase (start with proestrus)

LH surge or onset of receptivity to mating

When does proestrus end in the dog?

Proestrus

What phase does this describe in the dog?:

1. Follicular development

   1. Multioocytic follicles (5-14% with 2 to 17 oocytes)

Proestrus

What phase does this describe in the dog?:

1. E2 rises and peaks during late ___ (from 5-15 pg/mL to 40-120 pg/mL)

2. Testosterone increase

3. LH and P4 at basal level

4. FSH decreases

Increasing edema in vulva and vagina, change in color of mucosa from pink to white, serosanguineous discharge, attraction of male, not receptive to male until late proestrus

What clinical signs and behavior changes can you notice when a dog is in proestrus?

Proestrus

Which phase in the estrous cycle of the dog does this vaginal cytology describe?:

1. Early proestrus: parabasal cells

2. Mid-proestrus: small, then large intermediate squamous cells

3. Late proestrus: large cornified cells

4. Presence of RBCs, bacteria

5. Rare WBCs

CL formation

When does estrus end in the dog?

Estrus

Which phase in the dog does this describe?:

1. Preovulatory luteinization follicles

2. Ovulation of immature oocytes

3. Resumption of meiosis in the oviduct

Estrus

Which phase in the dog does this describe?:

1. E2 drops

2. P4 increases

3. LH surge: marks beginning of ___

Earlier, immature

1. Ovulation in the dog

   1. Follicles require LH receptors ___ than other species = preovulatory luteinization

   2. Primary oocytes are ovulated 48-60 hours post-LH surge

   3. ___ oocytes in prophase I

Decreased edema in the vulva, serum-like vulvar discharge, receptive to male, actively seeking males, wrinkling and crenulation upon vaginal exam

What clinical signs and behavior changes can you notice when a dog is in estrus?

Vulvar winking, tail flagging, ipsilateral limb flexion

Three reflexes that mark receptivity in the dog

Estrus

What phase in the estrous cycle does this cytology describe in the dog?:

1. No longer full or maximal cornification

2. Appearance of non-cornified cells

3. Possible bacteria

4. No WBCs or RBCs

2-4 days after ovulation

Optimal fertility window for dogs

Natural mating, fresh semen, frozen semen

Types of breeding management

Progesterone testing, vaginal cytology, vaginoscopy

Diagnostic tests used in clinical practice

True

True or false?:

Diestrus is the same length in pregnant and non-pregnant female dogs.

Diestrus

Which phase in the dog do these hormone changes describe?:

1. P4 peak (15-90 ng/mL 15-30 days after LH surge)

2. E2 and FSH are low

3. LH pulses

4. Prolactin increases at the end

Diestrus

Which phase in the dog does this physiology describe?

1. CLs formation

   1. Pseudopregnancy (overt or covert)

Diestrus

Which phase in the dog does this vaginal cytology describe?:

1. 50% parabasal and intermediate cells on primary days of diestrus

2. Abundant WBCs

Decreased vulvar swelling, mammary development and lactation towards the end, female not receptive

What clinical signs and behavior can be observed when a dog is in diestrus?

Luteal, prolactin

In the dog, progesterone is entirely of ___ origin and supported by ___.

Pseudopregnancy

Hyperresponse of the mammary gland with lactogenesis, lactation, and behavioral changes (nesting, digging, protective behavior)

May also happen after ovariectomy is done during luteal phase

Anestrus

Obligate stage in the dog; either post-whelping or post-diestrus

Anestrus

Which phase in the dog does this physiology describe?:

1. Antral follicle development

2. CL regression

3. Endometrial repair (lower fertility if <90 days)

Anestrus

Which phase in the dog do these hormone changes describe?:

1. E2 low until late in the phase

2. P4 low (<1ng/mL)

3. LH and FSH pulses increase in late phase

Anestrus

Which phase in the dog does this vaginal cytology describe?:

1. Few cells, not cornified

2. >90% parabasal cells and intermediate

3. Few WBCs and bacteria

Proestrus (<1 day), estrus (5-7 days), interestrus (8-9 days), diestrus - pseudopregnancy (40-45 days), diestrus - pregnancy (63-65 days), anestrus

List the six stages of the feline estrous cycle and their lengths.

Proestrus

Which phase is not always present in the feline estrous cycle?

Proestrus

Which phase in the cat does this physiology describe?:

Follicle cohort recruitment (2-7 per ovary)

Proestrus

Which phase in the cat does this hormonal change describe?:

E2 rising

Rubbing, vocalizations, affection (no sanguineous discharge, vulvar swelling, and abrupt changes in vaginal cytology like the dog)

What clinical signs and behavior could you observe when a cat is in proestrus?

Proestrus

Which phase in the cat does this vaginal cytology describe?:

<50% cornified cells and mainly small to large intermediate cells

Estrus

Which phase in the cat does this physiology describe?:

1. Development of dominant follicles ready to ovulate

2. LH surge (if mating occurs)

Estrus

Which phase in the cat does this hormonal change describe?:

E2 peak (>20 pg/mL)

Receptivity to the male, crouching, lordosis, vocalization, restlessness

What clinical signs and behavior can be observed when a cat is in estrus?

Timid, bottom of hierarchy

Why could a cat experience an absence of estrous signs?

Overlapping waves of follicles

Signs of extended estrous behavior in the cat

Estrus

Which phase in the cat does this vaginal cytology describe?:

1. No RBC (except for vaginitis) or WBC → 75% cornified superficial cells

2. Parabasal cells disappear by Day 4 of estrus (“clearing”) until 5 days after end of estrus

Nucleus becomes pyknotic but does not disappear completely, no RBCs or WBCs in cats, clearing until 5 days after end of estrus

How does vaginal cytology in a cat in estrus differ from vaginal cytology in a dog in estrus?

Progesterone testing, vaginal cytology, vaginoscopy

Diagnostic tests used in clinical practice for dogs who are being bred

Rolling, licking the vulvar area, rubbing on objects

Post-coital reaction of queen

23-32 hours

How many hours after mating does ovulation occur in the queen?

Higher

The more matings that occur in cats, the ___ the chance of ovulation occurring.

hCG, mechanical stimulation of the vaginal mucosa

How can induction of ovulation occur in the queen other than mating?

Interestrus

What phase in the estrous cycle does the queen enter if she does not ovulate?

Interestrus:

Which phase in the cat does this physiology describe?:

Atresia of mature follicles

Interestrus

Which phase in the cat does this hormonal change describe?:

Plasma estradiol levels drop to <20 pg/mL

Interestrus

Which phase in the cat does this vaginal cytology describe?:

1. Intermediate cells (48%), a decreased percentage of superficial cells (cornified cells still present!)

2. Presence of non-cellular debris

Diestrus

What phase in the estrous cycle does the queen enter if she ovulates but does not get pregnant?

Diestrus

What phase in the cat does this physiology describe?:

1. CL formation

2. Possible follicular formation (similar to the horse)

Diestrus

What phase in the cat do these hormonal changes describe?:

1. No preovulatory rise in P4 (different from the dog)

2. No pseudopregnancy as intended in dogs

Passive and not receptive to the male

What behavior can you observe from a cat who is in diestrus?

Diestrus

Which phase in the cat does this vaginal cytology describe?:

1. Intermediate cells

2. Parabasal cells

Diestrus

Which stage in the feline estrous cycle is also known as pseudopregnancy (to distinguish it from the luteal phase that occurs if the queen is pregnant)?

Anestrus

Which stage of the feline estrous cycle may not be present in indoor cats?

Anestrus

Which phase of the feline estrous cycle does this physiology describe?:

Absence of cyclicity in the late autumn and winter months

Anestrus

What phase of the feline estrous cycle do these hormonal changes describe?:

FSH, LH, E2, and P4 at baseline

Anestrus

What phase of the feline estrous cycle does this vaginal cytology describe?:
Intermediate cells

Shyness, inexperience, distraction

Why might cats be unable to mate?

Fresh or frozen semen, hCG

What can you use for artificial insemination in cats?

52-74 days from first/last mating

Average gestation length in cats

57-72 days from 1st mating

Average gestation length in dogs

Lactational anestrus

After queens give birth, they go into ___ until around 10 days post-weaning.

Prolactin, LH

What two hormones function as luteotropic factors in the dog?

Progesterone

In the dog, the concentration of ___ is similar in diestrus and during pregnancy.

PGF2alpha

In the dog, prepartum luteolysis is caused by ___.

Decreases

8 to 24 hours before parturition in the dog, rectal temperature ___ [increases or decreases] by 1 degree Celsius.

Prolactin

In the dog, ___ increases towards the end of pregnancy and during lactation.

Relaxin

In the dog, ___ peaks at 2-3 weeks before parturition and is present until 4-9 weeks after parturition.

1. Used as pregnancy diagnosis test (not early pregnancy!)

Physiologic alterations in the pregnant dog

1. Anemia normocytic, normochromic (7-9 weeks)

2. Increased HR, cardiac output, gastric emptying time, renal plasma flow, cholesterol (3-8 weeks), insulin resistance (55 days)

3. Decreased hemoglobin, tp, gastric motility, BUN, creatinine, serum calcium (56 days)

Ovaries, ovaries, placenta

In the dog, P4 is sourced from the ___, while in the cat, P4 is sourced from the ___ and the ___.

Prolactin

Which hormone in the pregnant queen?:

Increase by 35 days, plateau 50 days, further increase at parturition and lactation

Relaxin

Which hormone in the pregnant queen?:

Produced by fetoplacental unit; increase by 25 days, plateau 30-35 days, decline 10-15 days before partum

Prolactin, relaxin

Which two hormones are higher in pregnant queens than in pseudopregnant and non-pregnant queens?

Stage 1

Which stage of parturition?:

1. Uterine contraction and cervical dilation

   1. Anorexia, restlessness, panting, nesting

Dog: 6-12 hours; cat: 4-42 hours

How long is Stage 1 of parturition in the dog vs. the cat?

Stage 2

Which stage of parturition?:

Water bag bursts, abdominal straining, Ferguson’s reflex

Dog: 2-6 hours (up to 24 hours); cat: 0.5-2 hours (up to 24 hours)

How long is Stage 2 of parturition in the dog vs. the cat?

Stage 3

Which stage of parturition?:

Expulsion of fetal membranes

5-15 minutes after each puppy/kitten

How long is stage 3 of parturition in dogs and cats?