Canine Reproductive System

Reasons for euthanasia

Lost pets / given up (behavioral)

Overbreeding

Amount dead from rabies in India

>20,000 per year - 80% of world’s cases (from feral dogs)

Rabies in India

government reluctant to collect and kill feral dogs

• half of female dogs have a litter a year

• program to surgically sterilize 8 million

Gonads

(aka testes) - Male Reproductive system

• produces sperm and secretes hormones

Male system of ducts

Epididymis, ductus deferens, ejaculatory ducts, urethra

• transport and store sperm, assist in maturation, conveys to exterior

accessory sex glands - male

Seminal vesicles, prostate, bulbourethral glands

• adds secretions to semen

Supporting structures - male

Scrotum supports testes and penis delivers sperm into female reproductive tract

Male Reproductive Tract of the Dog

Lacks accessory sex organs (seminal vesicle, bulbourethral glands)

• only accessory organ is the prostate

• has an os penis

Male dog puberty

Average age is 9 months old

• 5-12 months depending on breed

Male reproductive endocrinology

Hypothalamus releases GnRH into circulatory system, which triggers release of pituitary LH and FSH - stimulates testosterone production and sperm production

Ovary - females

produces oocytes, secretes hormones

Oviduct - female

pick up oocytes, transports them and fertilized egg/embryo, site of fertilization, nourishes conceptus prior to implantation

uterus - female

site of embryo implantation and development; expulsion of fetus at birth

Vagina - female

copulatory organ, site of semen deposition, fetus transits through at birth

Mammary glands - female

nourishment of newborn

Reproductive tract parts - female dogs

Ovaries in the oviduct

Uterine horn

Uterine body with the cervix, vagina, urethral opening

Lips - constrictor vestibuli, the inside is the clitoris, the fossa clitoridis, and the vulva

Female dog puberty

average age is 9-12 months

• lasts 6-24 months (varies per breed)

Monoestrous ovarian cycle

One estrous during breeding cycle - interval from cycle to cycle varies among breeds and different environmental cues

• average 7 months

ovulation

ova are released from the follicles approximately 2-3 days following initiation of LH surge

Fertilization

ovulated ova are not ready for fertilization as they must complete meiosis 1 - therefore not fertilized until day 4-7 following LH surge

Pregnancy in dogs - length

63 days (similar in all breeds)

Pregnancy detection

Abdominal palpation at 3-4 weeks

Ultrasound after day 16

Neutering of male dogs

a lot of advantages

• widely accepted worldwide

• effective, safe, cheap

• protects against BPH

  • increases risk for osteosarcoma

Benign prostatic hyperplasia

overgrowth of the prostate that is common in both old male dogs and men

• dependent solely on testosterone

  • prevented and treated by castration

BPH - humans vs dogs

Urine flow problems vs Incontinence

Osteosarcoma

malignant bone tumor that mostly impacts large/giant breeds

Relationship between gonadal hormone exposure and risk for osteosarcoma

Inverse relationship between gonadal hormone exposure and risk

Osteosarcoma - castration statistics

Males castrated before one year have 4x risk of intact males

• females have 3x risk

Neutersol

Zinc glutamate compound for direct injection into testes

• stops sperm production

  • no longer legal in the US

ConaCon (GnRH vaccine)

GnRH conjugated to another molecule (KLH) to make it immunogenic

• used on dogs and cats

Spaying

removal of ovaries and uterus

• widely accepted, cheap

• protects against mammary tumors

• increases risk for osteosarcoma, obesity

Sperm Antigens - females

concept should work also work in females

• some infertile women have anti-sperm antibodies

Zona Pellucida Proteins (ZP3)

Works by blocking function of protein - sperm receptor on the glycoprotein coat of the oocyte

• effectiveness inconsistent

  • variety of species!

Gold standard for contraception

spaying and neutering