THERIO 2: Canine

TERM: question. DEFINITION: answer. Sorry for censorship of v4gina due to Knowt's profanity filter.

Describe the anatomy of the vestibule?

Area between vulva and v4gina which contains the urethral tubercle on the cranioventral floor (near the vaginovestibular junction, a narrow separating band).

Describe the anatomy of the v4gina?

Bottle-shaped, extending from uterus to vestibule (narrower cranially) at a similar length to the uterine horns. Has longitudinal mucosal folds.

Describe the anatomy of the cervix?

Smooth muscle structure between v4gina and uterine lumen, 1.5-2cm long and extending 1/2cm into the v4gina.

How does the uterus histologically change during the estrus cycle?

Proestrus / estrus: endometrial thickness increases

Diestrus: proliferation of the endometrial glands

Late diestrus, anestrus: normal tissue

What age does puberty occur?

Small breeds: 6-10 months.

Large breeds: <=25 months.

Why is the first estrus different to the rest?

Usually shorter and may be intermittent. Female may not display full signs of estrus behaviour.

Are dogs seasonal breeders?

Typically no (cycle every 4-12 mos), with the exception of the Basenjii which is autumn monoestric. Naturally, wild canines are spring monoestric.

What kind of estrus cycle do dogs have?

Monoestrous (prolonged anestrus period, typically lasting 4-12 mos but is variable down to the individual level).

What are the four stages of the canine estrus cycle and their average length?

Proestrus (9d), estrus (9d), diestrus (56-90d), anestrus (4mos).

Changes to the female during proestrus - physically apparent

GROSS - Swollen, edematous vulva / vaginal folds with serosanguinous discharge. Attracts and flirts with males but refuses mounting.

HISTO - Uterus has mixed epithelial cells and RBCs, transitioning to a thicker cornified (superficial) form.

Changes to the female during proestrus - physiologically apparent

Growing / developing follicles. High estrogen, low progesterone and increasing LH.

Changes to the female during estrus - physically apparent

GROSS - Reduced, softer vulval swelling with straw-coloured discharge and crenulated vaginal folds. Attracts males and allows for mounting.

HISTO - Mostly superficial (keratinised) cells with few RBCs.

Changes to the female during estrus - physiologically apparent

Follicles luteinise, ovulation / secondary meiosis occurs, corpora lutea form. LH surge occurs, with increasing progesterone and low estrogen.

When is the recommended time in the estrus cycle to breed?

Post LH surge (when vulvar edema decreases) as ovulation occurs about 48 hours later. Peak fertility is around day 5, if b1tch shows no interest by day 4 can use A.I.

What are examples of sexual behaviour from both sexes?

Female: flagging, seeking male, urine marking, lordosis.

Male: mating efforts, licking vulva, vocalisations, increased movements / escape efforts.

How do hormones change during diestrus?

Increase in progesterone (up to 2-30ng/mL), demise of CLs + refraction to PGFa. Open females will have a slower P4 decline, and pregnant females will have an elevated relaxin >30 days (i.e., more rapid decline).

What symptoms may indicate pseudopregnancy?

Weight gain / abdominal enlargement, mammary development, lethargy and appetite changes.

Canine pregnancy by the numbers (implantation, gestation, litter size)

Embryos migrate transuterinely and implant at about 18-20d. Gestation is about 65d (+-1) from LH surge. Litter size is usually 2-10, increasing with maternal body size.

Presentation of anestrus

No reproductive behaviour, small vulva with minimal discharge. Low progesterone, estrogen. In late anestrus, there will be increasing LH pulses and FSH levels.

What is the natural tie of copulation?

The male’s bulbis glandis enlarges and gets wedged in the v4gina, causing the sexes to be stuck together for 5-30 mins, and allowing for multiple ejaculations to occur.

What is the normal composition of the canine ejaculate?

Generally low concentration (mixed rich and clear fractions) - should have up to 60% normal anatomy and motility.