Lecture on the Estrus Cycle in Cattle

Introduction

• Speaker: Megan Bol
• Topic: Estrus Cycle focusing on cattle

Definition

• Estrus Cycle: Correlated phenomena of the endocrine and reproductive systems from the beginning of one period of estrus to the next.
• Polyesterous: Cows are polyesterous, meaning they go through multiple estrus cycles throughout the year.

Stages of the Estrus Cycle

• Total Duration: Approximately 21 days in cattle.
• Stages:
  1. Proestrus
  2. Estrus
  3. Metestrus
  4. Diestrus

Phases of the Estrus Cycle

1. Follicular Phase
   • Composes the Proestrus and Estrus stages.
   • Primary Structure: Follicle.
2. Luteal Phase
   • Composes the Metestrus and Diestrus stages.
   • Primary Structure: Corpus luteum.

Hormones Involved

• Estradiol (Estrogen)

  • Highest during Estrus and Proestrus stages (Follicular Phase).
  • Functions:
    • Induces heat, leading to an LH surge.
    • Stimulates growth of endometrium and myometrium.
    • Develops mammary gland.

• Progesterone

  • Highest during Metestrus and Diestrus stages (Luteal Phase).
  • Functions:
    • Maintains pregnancy.
    • Inhibits LH and FSH to prevent new estrus cycle.

• Luteinizing Hormone (LH)

  • Surge before ovulation.
  • Promotes ovulation.
  • Triggered by high levels of estradiol.

• Follicle Stimulating Hormone (FSH)

  • Promotes growth of follicles.
  • Leads to new ovulations and cycles.

• Prostaglandin F2 Alpha (PGF2α)

  • Released if no pregnancy occurs.
  • Causes luteolysis (regression of corpus luteum).
  • Prepares for the next cycle.
  • Note: If pregnancy occurs, progesterone remains high to maintain it.

Conclusion

• Overview of the estrus cycle in cattle.
• Focused on hormones involved and their roles.
• The cycle is like a recipe with each hormone playing a key part.

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Thank you for listening.