Animal Reproduction Economic Importance

Study Notes

Reproduction is twice as impactful on economic returns than carcass performance and growth.
Reproductive efficiency is judged by the number of calves, lambs per 100 breeding females, and pigs per litter.
Understanding reproduction is crucial for optimizing reproductive rates.

Ovaries: Produce ova (eggs) and hormones (estrogen from follicles, progesterone from the corpus luteum).
Ovaries (cont.): Follicles develop eggs; Graafian follicles mature and release eggs (ovulation); the corpus luteum forms after ovulation and produces progesterone, essential for maintaining pregnancy.
Oviducts (Fallopian tubes): The infundibulum guides eggs into the oviduct; sperm meet eggs here for fertilization; embryos move to the uterus after fertilization.
Uterus: The "womb," varying in shape across species (sow: long horns; mare: short horns, large body; cow: large horns, small body). Houses developing fetuses until birth (parturition).
Cervix: The gate between the uterus and vagina; undergoes changes during estrus and parturition.
Vagina: Organ of copulation, birth canal, and shared passage for urinary and reproductive systems.

Unlike other farm animals, hens don't suckle young, lay eggs externally, and lack defined estrous cycles or pregnancy.
Only the left ovary and oviduct develop in mature hens.
The ovary is a yolk cluster near the left kidney; the oviduct extends to the cloaca.

The hen's oviduct has five sections: infundibulum (receives yolk), magnum (adds thick albumen), isthmus (adds shell membrane), uterus (shell gland; adds thin albumen, shell, and pigments), and vagina.
Egg laying takes 24 hours; a new yolk is released 30 minutes after laying. Fertilized eggs incubate for 21 days.

The hypothalamus releases GnRH (gonadotropin-releasing hormone), stimulating the anterior pituitary.
The anterior pituitary releases FSH (follicle-stimulating hormone), promoting follicle development, and LH (luteinizing hormone), triggering ovulation.
Follicles mature and release estrogen, influencing GnRH and female sexual behavior. An LH surge causes ovulation.

The estrous cycle is a predictable pattern of reproductive events. It begins with estrus (heat) and ends with the next estrus (if not pregnant).
Cycle types: polyestrus (year-round; cattle, swine), seasonally polyestrus (seasonal; sheep, goats, horses; manipulated by light and melatonin), and monoestrus (single cycle; dogs).
FSH increases follicle size and estrogen production. Estrus is when females accept mating. Ovulation follows estrus, triggered by an LH surge; LH also stimulates progesterone production by the corpus luteum.

If pregnant, the corpus luteum continues progesterone production.
If not pregnant, the uterus releases PGF2a (prostaglandin), causing the corpus luteum to regress, dropping progesterone levels.