Combined set for theriogenology

Age of puberty of a cow

8-12 months

Age of puberty of a horse

15-24 months due to seasonal effects

Type of placenta in a cow (gross and histology)

Gross: Cotyledonary

Histo: Epithelio-chorial

Type of placenta in a horse (gross and histology)

Gross: Diffuse/microcotyledonary

Histo: Epithelio-chorial

Type of estrus cycle in a cow

Polyestrus

Type of estrus cycle in a horse

April-September (can manipulate with lighting)

Length of estrus cycle in a cow

21 days

Length of estrus cycle in a horse

21 days

Duration of estrus in a cow

12-18 hrs

Duration of estrus in a horse

4-7 days

When does ovulation occur in a horse, in relation to estrus?

24-48 hours BEFORE the end of estrus

When does ovulation occur in a cow, in relation to estrus?

4-16 hours AFTER the end of estrus

When is the best time to AI cows?

- Best to get sperm in BEFORE ovulation or within 6 hours after
- Best to inseminate in last half of standing heat

What is the AM:PM rule for AI?

If the cow is seen in estrus this AM, then AI this PM and tomorrow AM (get the semen in before she ovulates)

When is the best time to breed a mare for live cover, AI and frozen semen?

Live: Breed every other day when she will stand

AI: Best to get sperm in BEFORE ovulation, after she has been in estrus for at least 2 days

Frozen semen: As close to ovulation as possible because frozen thawed semen doesn't live very long

Mechanism of ovulation in a cow

Spontaneous

Mechanism of ovulation in a horse

Spontaneous

Time of ovulation in a cow

4-16 hours after estrus

Time of ovulation in a horse

24-48 hours before end of estrus

Ovulation rate (# of ova) in a cow

1

Ovulation rate (# of ova) in a horse

1-3

Transit time of ovum in oviduct in a cow

5 days

Transit time of ovum in oviduct in a horse

5-6 days

Attachement in a cow

20 days

Attachement in a horse

25-26 days

Do pseudopregnancies occur in cows?

Not reported

Do pseudopregnancies occur in horses?

Not reported

Gestation length of cows

278-293 days (9 months)

Gestation length of horses

330-345 days (11 months)

Chromosomes in cows

60

Chromosomes in horses

64

Parts of the female repro tract

- Ovaries
- Oviduct
- Uterus
- Cervix
- Vagina
- External genitalia (vulva)

Which parts of the female repro tract are considered "internal tubular"

- Oviduct
- Uterus
- Cervix
- Vagina

Four tissue layers of the female repro tract

1. Serosa (outer most layer) aka perimetrium

2. Muscularis aka myometrium (largest)

3. Submucosa aka endometrium

4. Mucosa (inner most layer) aka endometrium

Two strata of uterine endometrium

1. Stratum cellulosum - superficial layer, highly cellular, epithelium

2. Stratum spongiosum - deeper and thinner layer, loose CT to allow edema in diestrus

Explain the basic structure of the ovary

Medulla and cortex are reversed, so the medulla is inside and the cortex is outside (except for in the horse)

Where does ovulation occur?

At only one location in each ovary, at a specific anatomic location called an ovulation fossa

What is the end of the oviduct called?

The infundibulum

What is the middle of the oviduct called? What occurs here?

Ampulla
Fertilization

What is the bottom of the oviduct called? Where does it connect to?

Isthmus
It connects to the uterus via the utero tubal junction

Functions of the oviduct

- Transports newly ovulated oocyte and sperm to the ampulla, where fertilization occurs
- Substances secreted by oviductal mucosa provide the optimum environment for the unattached, unfertilized, oocyte and embryos
- Also helps in sustaining functions of spermatozoa until arrival of an oocyte
- Utero tubal junction prevents polyspermy

Metritis versus endometritis

Metritis: Inflammation of the endometrium, underlying glandular tissues and muscular layer

Endometritis: Inflammation of the endometrium and underlaying glandular tissue

Functions of the uterus

- Transport and storage of sperm
- Luteolysis and control of cyclicity
- Environment for pre attachment embryos
- Maternal fetal interactions through placenta
- Expulsion of the fetus and fetal placenta via uterine contractions

What does the cervix of cows, ewes and sows have?

Distinct cervical rings

What does the cervix of mares have?

Longitudinal folds

Functions of the cervix

- During estrous cycle, cervix produces mucus that lubricates the vagina for copulation
- Foreign material introduced during copulation and some sperm are flushed out by cervical mucus
- Reduction on the number of spermatoza due to low pH
- During pregnancy, the cervix isolates conceptus from external environment through a 'cervical seal'
- In non-pregnant animals, cervix also protects against bacterial and fungal infections
- Is a copulatory organ in some species, meaning fertilization occurs here (pigs)

What is the area called where the cervix protrudes into the anterior vagina

The fornix

Where is the clitoris located

In the ventral commissure that houses the clitoris fossa, and that is where the clitoris is

Close apposition of blood vessels and lymphatics in the uterus allows what?

The transfer of hormones

What does the vagina produce during estrous?

Mucus

What is a hormone?

A substance produced in one part of the body that diffuses or is transported to another part of the body where it influences activity and tends to integrate components of the organism

Autocrine versus paracrine versus endorcine

Autocrine: Hormone acts on the same cell that produced it

Paracrine: Hormone acts locally by diffusing to close by cells

Endocrine: The hormone is distributed in blood and binds to distant target cells

Characteristics of reproductive hormones?

- Most are secreted in a pulsatile fashion
- Secreted periodically (female) or constitutively (male)
- Effective even in minute quantities
- The half life is relatively short
- They regulate intracellular biochemical reactions in reproductive and some non-reproductive tissues

What can reproductive hormones do?

- Control other hormone release
- Stimulate gonads
- Stimulate sexual development, sustain gonadal function, alter secondary sex characteristics
- Maintain pregnancy, initiate and sustain parturition and lactation
- Control ovarian cyclicity

Three anatomic sources of repro hormonrs

1. Hypothalamic
2. Pituitary
3. Gonadal

Four modes of actions of repro hormones

1. Neurohomrones
2. Releasing hormones/factors
3. Gonadotropins
4. Metabolic/sexual stimulants

Three biochemical classifications of hormones

1. Peptides
2. Steroids
3. Fatty acid and derivates

Function of GnRH in females

Release of FSH and LH from anterior lobe of the pituitary

Function of luteinizing hormone (LH) in females

Stimulates ovulation, CL formation and progesterone secretion

Function of follicular stimulating hormone (FSH) in females

Follicular development and estradiol synthesis (main estrogen)

Function of prolactin in females

Lactation, maternal behaviour

Function of oxytocin in females

Uterine motility and milk ejection; luteolysis

Function of estradiol (estrogen) in females

Sexual behaviour, elevates secretory activity of the entire repro tract, elevates uterine motility

Function of progesterone in females

Maintains pregnancy

Function of testosterone in females

Substrate for estradiol synthesis, abnormal sex characteristics

Function of inhibin in females

Inhibits FSH secretion

Function of activin in females

Stimulates FSH secretion

Function of PGE2 in females

Ovulation, stimulates progesterone production from CL

Function of PgF2 alpha

Luteolysis of CL, ovulation

Function of human chorionic gonadotropin in females

Facilitate production of progesterone by ovary

Function of equine chorionic gonadotropin in females

Causes formation of accessory corpora lutea

Function of placental lactogen in females

Mammary gland stimulation

Where do protein hormones act?

Via a plasma membrane receptors on the target cell

Where do steroid hormones act?

Via nuclear receptors in the target cell

Estrus cycle results from a complex hormonal interaction between what three organs?

1. Hypothalamus
2. Pituitary
3. Ovary

called the "hypothalamic-pituitary-ovarian axis"

Three types of estrous cycles

1. Polyestrous
2. Seasonally polyestrous
3. Monoestrous

Four stages of the estrus cycle in cows and horses?

1. Proestrus
2. Estrus
3. Metaestrus
4. Diestrus

Two phases of the estrus cycle

1. Follicular (pro estrus + estrus)
2. Luteal

Dominant structure and hormone in the follicular phase of estrus?

Structure: Large antral follicles

Hormone: Estrogen produced by pre-ovulatory follicles

What are the four things that the follicular phase is characterized by?

1. Elevated GnRH release
2. Follicular growth
3. Sexual receptivity
4. Ovulation

Dominant structure and hormone in the luteal phase of estrus?

Structure: Corpora lutea

Hormone: Progesterone

What occurs in pro estrus?

Maturation of ovulatory follicles and estrogen secretion

What occurs in estrus?

Sexual receptivity and peak estrogen secretion

What occurs in metaestrus?

Corpus luteum formation and beginning of progresterone secretion

What occurs in diestrus?

Sustained luteal secretion of progesterone

Behaviour changes during estrus

- Standing to be mounted
- Mounting other animals
- Restlessness
- Licking or sniffing other animals
- Winking
- Increased vocalization and urination
- Chin pressed on rump or back of another animal

Visible signs during estrus

- Cervical mucous discharge from vulva
- Swelling of the vulva
- Reddening of vaginal mucosa

Strucutral changes that can be palpated during estrus

- Number and size of antral follicles
- Presence of CL
- Tone of uterus (species specific)

Cow versus mare uterine tone in estrus

Cow: More toned

Mare: Less toned

What cells produce estrogen?

Granulosa cells of the ovary (produced specifically by growing follicles)

What is the main hormone of estrus

Estrogen

What is the main hormone in diestrus and pregnancy

Progesterone

What produces progesterone

CL

Spontaneous versus reflex ovulators

Spontaneous: Ovulate with spontaneous frequency and do not require copulation. Ovulation is brought about by hormonal drive.

Reflex: Requires stimulation of vagina or cervix for ovulation.

What is ovulation?

A cascade of physiological and biochemical changes that culminate in rupture of large antral follicles that release oocytes

Why is the ovary both endocrine and exocrine?

Endocrine: Estrogen, progesterone going into the blood

Exocrine: Ovulated oocyte

Where are the follicles in the ovary

In the cortex

8 phases of follicular development (from start to finish)

1. Primordial follicle

2. Primary follicle

3. Secondary follicle

4. Pre-antral follicle

5. Antral follicle (have an antral cavity)

OVULATORY PROCESS:

6. Corpus haemorrhagicum (after ovulation this is the ruptured follicle)

7. Corpus lutem

8. Corpus albicans

9. Luteinized unovulated follicles/cysts

Two cell types in an ovarian follicle

1. Ganulosa
2. Theca

What is in each follicle?

A single oocyte