Female Reproduction

Bubbles called follicles in ovaries contain eggs maturing for ovulation.
Cow ovaries typically have fewer mature follicles compared to sows due to reproductive needs.
- Cows generally have one baby needing only one egg.
- Cows possess many immature follicles that can mature into ovulatory follicles.

Cystic follicles do not rupture as expected; they grow excessively and resist hormones needed for ovulation.
After ovulation, the structure that follows is the corpus luteum, which is solid and yellow in color (Latin for "yellow body").
- Produces progesterone following ovulation.

Superovulation is often used in procedures like embryo transfer.
- Administering FSH (Follicle Stimulating Hormone) promotes multiple follicles to develop.
- After ovulation, these follicles lead to the formation of corpora lutea that produce progesterone.

Responsible for the transport of eggs and sperm; the site of fertilization.
No implantation occurs here; tubal pregnancies (implantation in oviduct) are dangerous.

Transports sperm; site for embryo implantation and nourishment.
The uterus also produces prostaglandin to regress the corpus luteum, halting progesterone production at parturition.

Four main types of uterine shapes:
- Duplex: Two uterine horns and two cervices (in smaller mammals).
- Bipartite: Two uterine horns and one cervix (common in small rodents).
- Bicornuate: One uterine body, two horns, and one cervix (found in most livestock).
- Simplex: One uterine body and one cervix (humans).
The uterus shape influences reproductive processes across species.

The cervix serves as a passage for sperm and fetus; it maintains structure due to its cartilaginous nature.
- It closes tightly during pregnancy to prevent infections.
- Dilates during estrus and parturition.
The vagina is the copulatory organ, site for semen deposition in natural service for cattle.

Females are born with a finite number of oocytes, which mature post-puberty.
- Initially, many primary follicles are recruited, but most degenerate before reaching maturity.
The dominant follicle (graafian follicle) ruptures due to LH surge and releases the ovum.

Hormones regulate the ovarian cycle:
- Estrogen: Produced by mature follicles; initiates estrus behavior and physical changes in females.
- Progesterone: Produced by the corpus luteum; prepares the uterus for pregnancy.
GnRH from the hypothalamus stimulates the anterior pituitary to release FSH and LH.

Estrous cycle in cattle is approximately 21 days.
Estrus lasts about 18 hours; ovulation occurs 20-40 hours post-estrus onset.
- Essential for the timing of breeding to ensure fertilization occurs while the egg is viable.

Estrogen: Drives estrus behavior and promotes sexual receptivity.
Progesterone: Supports gestation and maintains pregnancy by thickening the uterine lining and initiating placenta development.
Prostaglandin: Regresses the corpus luteum to stop progesterone production.
Prolactin: Initiates lactation in females post-birth.
Relaxin: Allows muscle relaxation for birth; aids in ease of delivery.
Oxytocin: Responsible for uterine contractions and milk letdown during lactation.

AI allows for controlled breeding using collected and preserved semen.
- Maximizes genetic potential across diverse herds.
- Reduces the risk of reproductive disease transmission.
- Enables breeding from superior genetics, including deceased or injured sires.

Monitor for return to estrus, manual palpation, blood or milk tests for hormones, and ultrasound.
Early confirmation is beneficial for managing breeding cycles effectively.

Enhances the reproductive efficiency of superior females by allowing multiple offspring from one donor.
- Involves synchronized estrus cycles for both donor and recipient females.
Embryos are graded to determine viability; only healthy embryos are implanted or preserved.

Understanding the intricate hormonal and anatomical aspects of reproduction is critical for effective animal husbandry practices.
Advances in reproductive technologies such as AI and embryo transfer have significant implications for genetic improvement and animal breeding efficiency.