Animal Reproductive Biology Quiz

Coitus

• Coitus involves the insertion of the erect penis into the vagina, followed by ejaculation.
• The location of semen deposition varies depending on the animal: cattle, buffalo, mare, sow, and ram each have distinct areas.
• The ram's urethral process forces semen distribution, ensuring its effectiveness despite low volume.

Duration of Coitus

• Cattle and sheep have brief copulation lasting only a few seconds.
• Stallion copulation lasts 15-30 seconds.
• Dogs have a copulatory tie that can last 15-30 minutes.
• Swine exhibit a copulatory tie for an average of 3-8 minutes.
• Failure to ejaculate is common in swine.

Dangers of Coitus

• Young heifers can experience uterine injuries with overly large bulls.
• Lacerations and trauma can lead to post-coital swelling, bleeding, and straining.
• Artificial insemination is preferred for heifers' growth, while natural breeding is recommended for mature heifers.
• The first insemination should be natural to allow for size compatibility between the bull and heifer.
• Foreign breed pairings can lead to dystocia and oversized embryos.
• Artificial insemination is advised for situations where natural breeding poses risks.

Metrorrhagia

• Metrorrhagia is bleeding after coitus.
• While sometimes normal, it can indicate underlying issues.

Ovulation

• The maturation of an oocyte is known as ovogenesis.
• Meiosis I begins during fetal development, while meiosis I is completed after puberty, producing a secondary oocyte and the first polar body.
• The secondary oocyte then begins meiosis II.
• If fertilization occurs, meiosis II is completed, resulting in an ovum and a second polar body.
• Without fertilization, meiosis II doesn't complete.

Folliculogenesis

• The process starts with a primordial follicle and progresses through stages: primary, secondary, mature Graafian follicle, corpus luteum, and corpus albicans.
• The mature Graafian follicle houses the secondary oocyte and the first polar body.

Cumulus Oocyte Complex

• The cumulus oocyte complex comprises the oocyte, follicular fluid, zona pellucida, and corona radiata cells.
• These cells play a vital nutritive and protective role.

Zona Pellucida (ZP)

• The zona pellucida is a tough, acellular glycoprotein layer surrounding the oocyte and produced by the oocyte itself.
• It acts as a barrier to sperm penetration and has species-specific receptors to prevent fertilization by sperm of other species.

Corona Radiata

• The corona radiata is the outermost layer of cells around the oocyte.
• It's composed of cumulus oophorus cells.

Regulation of Follicular Growth

• Growth differentiation factor 9 (GDF9) is a protein produced by the theca cells, acting as a paracrine factor to stimulate granulosa cells.
• Growth differentiation factor 9B (GDF9B) is produced by both granulosa and theca cells, acting as an autocrine inhibitor for follicular growth.
• Activin is a hormone produced by granulosa cells, acting as a paracrine factor to enhance the growth and maturation of the dominant follicle.

Mechanism of Ovulation

• Estrogen levels rise during estrus, triggering LH release.
• The pre-ovulatory LH surge causes the expansion of the cumulus cell layer, separating the oocyte from the follicular wall.
• This surge also increases blood supply to the ovary and follicle, leading to vascular permeability.
• Plasminogen and prostaglandins enter the follicle through the increased permeability.
• Plasminogen activation converts plasminogen into plasmin, which degrades collagen and weakens the follicular wall.
• Prostaglandin E and F synthesis and release further contribute to muscle contraction and expulsion of the oocyte.

Fimbria

• Fimbria are finger-like projections on the fallopian tube's infundibulum.
• They move and contract for guiding the oocyte into the fallopian tube.
• Estrogen increases their activity.

Time of Ovulation

• Various animal species have different ovulation timings: cows (10-12 hours after estrus), mares (2 days before the end of heat), ewes (6-12 days before the end of heat), goats (4-6 hours before the end of heat), sows (24-48 hours after estrus), cats (induced 24 hours after coitus), and camels (induced 24-36 hours after coitus).

Fertilization

• Fertilization involves the union of a mature sperm and ovum to form a zygote.

Factors Facilitating Fertilization

• Sperm maturation in the epididymis, sperm capacitation, and the acrosomal reaction are essential.
• Sperm transport to the egg is a complex process influenced by fallopian tube length, location, and sperm motility.
• Ovum transport relies on fimbriae, follicular fluid, cilia, and muscle contractions.

Mechanisms of Sperm Transport

• Fertilization occurs at the ampullary-isthmic junction.
• Ejaculation in the dorsal fornix of the vagina, estual mucus for sperm movement through the cervix, and selection of sperm in the uterus are crucial steps.
• Oxytocin and prostaglandin in semen contribute to contractions for sperm transport.
• Sperm await the ovum at the ampullary-isthmic junction.
• Abnormal sperm are either phagocytized or lost via the cervix.

Cervical Mucus

• It protects, nourishes, and has antimicrobial properties.

Sperm Attachment to Fallopian Tube

• Temporary attachment to the fallopian tube epithelium for protection and capacitation.

Barriers to Sperm

• The cervix is a challenging barrier, due to mucus and the annular ring.
• The cortical reaction hardens the zona pellucida, preventing further sperm entry.

Syngamy

• Fusion of male and female pronuclei to form a zygote.

Abnormal Fertilization

• Polyspermy (multiple sperm penetration) leads to a triploid zygote, typically ending in death.
• Polygyny (maturation of the egg without the second polar body expulsion) also results in a triploid zygote.
• Gynogenesis (non-development of the male pronucleus) leads to a haploid embryo that dies.
• Androgenesis (non-development of the female pronucleus) results in a haploid embryo that doesn't develop.
• Ovum wandering can occur internally or externally, and is common in bitches.
• Superfecundation involves impregnation by two different males.
• Superfetation is the gestation of fetuses from separate ovulations, a rarer phenomenon.

Twins

• Identical twins (monozygotic) form when a single zygote splits into two, sharing the same sex and DNA.
• Fraternal twins (dizygotic) result from fertilization of two eggs by two sperm, sharing half of their DNA like regular siblings.
• Twin incidence rises with maternal age.