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Questions and Answers
What is the typical copulation duration for a stallion?
Which breeding method is recommended for heifers that have reached full growth?
What common risk is associated with copulation in younger heifers?
During which phase does meiosis I begin in ovogenesis?
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What is metrorrhagia in the context of coitus?
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What occurs to the secondary oocyte if fertilization takes place?
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What is the role of the zona pellucida surrounding the oocyte?
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What is the primary role of Growth Differentiation Factor 9 (GDF9) in folliculogenesis?
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Which structure is the final product after the ovulation of a mature Graafian follicle?
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What effect does increasing estrogen levels have during estrus?
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Study Notes
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.
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Description
This quiz covers the mechanics and duration of coitus in various animals, along with potential dangers associated with natural breeding. Learn about species-specific copulation times, injury risks, and the role of artificial insemination in reproductive health.
