Guinea Pig Reproduction - Anatomy & Physiology

Male

The male guinea pig is known as the Boar. The genital organs consist of the testes, accessory sex glands and the perianal & caudal glands. The perineal sacs are present in both sexes, but are more extensive in the male. They lie on either side of the anus and contain extensive caseous secretions, hair and skin debris.

Anatomy of the Male Guinea Pig

^{© L.Wilkie 2008}

Penis

• Os penis
• Caudoventral to the urethral opening is a pouch containing two horny styles (projections).
  • Evert externally during erection of the penis.

Testes

• Two testes
• Epididymis lies along the dorsolateral margin and has large fat bodies associated with its head and tail.
• Inguinal canal remains open throughout life.
• In mature, breeding boars the large testes lie in the scrotum either side of the genital opening.

Accessory Glands

The guinea pig has several accessory glands.

Vesicular glands

• Large, yellow-white vermiform sacs lying in the caudal peritoneal cavity dorsal to the bladder and extending cranially into the abdomen.
• They are long and coiled in appearance, filled with semi-solid seminal secretions.

Prostate gland

• Lies close to the base of the vesicular glands.

Coagulating glands

• Lie close to the base of the vesicular glands.

Bulbourethral glands

• Oval, paired glands which lie close to the urethra at the ischial arch.

Mammary Gland

• Pair of long inguinal nipples.
• Mammary glands rudimentary.

Sexual Maturity

• Puberty occurs at 3 months.
• Will show mounting behaviour from 1 month.

Female

The female guinea pig is known as the Sow.

Reproductive Tract

Anatomy of the Female Guinea Pig

^{© L.Wilkie 2008}

Ovary

• Ovaries are located caudolateral to the kidneys supported by a short mesovarium.
  • Main blood supply to the ovary is via the uterine artery.

Oviduct

• Oviduct lies in close contact with the ovarian bursa.

Uterus

• Bicornate uterus
  • Two uterine horns
  • Single cervix
  • Single vagina
    • Membrane covers vaginal opening except at oestrus and during parturition.

Attachments and Blood Supply

• Broad ligament (mesovarium, mesosalpinx and mesometrium) contains a lot of fat.
• Anastamoses between the uterine and ovarian arteries occurs in the mesentery.

Sexual Maturity

• Puberty occurs at 3 months.
• However, pregnancy has been known to occur at as early as 4-5 weeks.

Oestrous Cyclicity

• Polyoestrous
• Spontaneous ovulator
• Oestrous cycle length:15-16 days

Gestation and Offspring

Gestation

• Long gestation period: 59-72 days (depending on litter size)
• Placenta is haemochorial
• Receive all maternal antibodies through the placenta, not the Colostrum
• Placenta eaten by the dam and other guinea pigs after parturition.

Litter

• Litter size: 1-6
  • Precocious offspring
    • Fully furred at birth
    • Eyes open
    • Able to eat solid food as well as suckle from the mother.
    • Weaned at 3 weeks.
• No nest

Mammary Gland and Lactation

• Pair of long inguinal nipples.
• Divided into fine lobules, which open via a number of small ducts into one large duct to the exterior.
• Two teats
• Composition: 4% Fat, 8% Protein, 3% Lactose