Repro in the dog Flashcards
- Function of repro system in male dogs.
- Endocrine pathway?
- What do the Sertoli cells release to cause negative feedback on the endocrine pathway?
- Produce hormones.
- Produce, mature and deliver sperm.
- Produce hormones.
- HT releases GnRH»_space; Stimulates anterior pituitary to release FSH and LH»_space; FSH stimulates Sertoli cells in testes to produce sperm and LH stimulates Leydig cells in the testes to produce testosterone.
- Activin and inhibin and testosterone itself.
What does testosterone do?
Contributes to secondary male characteristics – stature, shape.
Sex behaviours:
– Mounting.
– Marking.
– Roaming.
– Competitive aggression towards other male dogs around females in heat.
- Oestrus pattern of bitches.
- Age of onset of puberty?
- Fertility peak age?
- Mono-oestrous w/ an obligatory anoestrus.
- Onset variable, mean 9 months of age.
- Age of fertility peak at around 2yrs old.
Oestrous cycle in the bitch.
- Pro-oestrus – 6-11 days.
- Oestrus – 5-9 days w/ ovulation on day 3.
- Luteal/progesterone dominated phase – 56-60 days.
- Anoestrus – months.
Oestrogen active and increasing in pro-oestrus, coming to a peak and causing ovulation, entering bitch into oestrus where oestrogen decreases as egg regresses, entering into luteal phase w/ formation of CL, then anoestrus w/ no hormonal activity.
What is happening in pro-oestrus in the bitch?
Ovarian follicular development.
Rising levels of FSH inducing oestrogen secretion.
Haemorrhagic vaginal discharge and swelling of the vulva.
Attractive to males.
Playful behaviour but aggressive if dog attempts to mount.
Increased urine marking.
Anxiety/agitation.
What is happening in oestrus of the bitch?
- Phase of increasing FSH, oestrogen ‘spike’ which turns the AP to secreting LH.
- LH surge induces progesterone secretion from ruptured follicle.
- Vaginal discharge becomes clear, vulva stays swollen.
- Ovulation occurs on average on day 3.
- Bitch allows dog to mount.
- Bitch presents perineum to dog and ‘stands’ with tail deviated to one side.
- Roaming/seeking/escaping to find a mate.
- Competitive aggression towards other females e.g. over male dogs, food, space, owner attention.
When is the optimal time to mate in bitches?
Subjective:
- Timing in oestrous cycle (start if pro-oestrus, standing oestrus).
– Maximal fertility from the day of ovulation to up to 4 days after ovulation.
- Vulvar softening.
- Vaginal impedometry (detection machine for thickness).
Objective:
- Hormone concentrations (oestrogen, LH, progesterone).
- Vaginal cytology.
- Vaginoscopy.
Hormone assays.
Oestrogen not reliable!
LH – no assays available.
Progesterone:
– Semi-quantitative in house.
– Quantitative in external lab.
– Every 2-day basis (2-fold increase).
Exfoliative cytology from the vagina…
1. Method.
2. What do we see on microscopy at anoestrus.
3. What do you see in early pro-oestrus?
4. Late pro-oestrus?
- Damp sterile swab.
- Must be vaginal smear (use guard or speculum), not vestibule.
- Diff-quick stain.
- Serial examination for stage of oestrous cycle.
- Damp sterile swab.
- Quiescent, very little cells – a few rounded nucleated cells –> parabasal cells, occasional leukocyte.
- Dramatic changes in lining. Thickening of vaginal mucus and increased layers of cells and RBCs. Increased parabasal cells.
- More smaller black dots and larger keratinised cells – angular cells (feature of oestrus).
- What do you see on microscopy at oestrus? – when is mating advised?
- What do you see in luteal phase.
- Angular cells – non-nuclear, cornified, large superficial squamous cells, fewer RBCs.
– Mating advised when >75% of the cells on the slide at 100X magnification have no nucleus. - Lots of polymorphic leukocytes, WBCs, few more parabasal cells, some remnants of epithelial keratinised cells
Factors of when to mate.
After ovulation – 48hrs for eggs to mature before they can be fertilised.
12 hours after ejaculation, fresh sperm cells are able to fertilise an egg.
Canine sperm cells can live for up to 5 days.
So mating just before ovulation can still produce puppies.
2 matings (24-48hrs apart) recommended.
How can we suppress oestrus to avoid pregnancy in bitches?
Surgically:
- Ovariectomy.
- Ovariohysterectomy.
Medically:
- Progestogens e.g. proligesterone (bad side effects). e.g. Ovarid.
- Androgens e.g. testosterone (no licensed preparations).
- GnRH agonists e.g. Deslorelin (Suprelorin implants) – only licensed for use pre-puberty at 12-16wks old –> stops heat for 12mths-3-4yrs.
– Takes 3-4wks to take effect.
How can male fertility be managed?
Surgically:
- Castration.
- Vasectomy.
Medical:
- Deslorelin implant – GnRH agonist.
- Use of Deslorelin acetate implant in male dogs.
- Use of Deslorelin acetate implant in prepubertal female dog.
- Use of Deslorelin acetate in male cat.
- Induces temporary infertility in healthy, intact, sexually mature male dogs.
Infertility for 6wk up to 6mths after initial treatment.
Treated dogs should be kept away from bitches on heat within first 6wks after initial treatment. - Induces temporary infertility to delay first oestrus in intact and healthy sexually immature female dogs. Should be administered between 12 and 16 weeks old.
- Induces temporary infertility and suppression of urine odour and sexual behaviours such as libido, vocalisation, urine marking and aggression in intact male cats from 3 months old.
Effects of neutering on undesirable behaviours.
Effects related to mounting, roaming, masturbation and urine marking in males.
Effects on competitive aggression, pseudocyesis related behaviour in females, UNLESS LEARNT.
NO effects on anxiety/fear, aggression, trainability.
Some behaviours may be exacerbated by neutering.
