Parturition, Estrus Cycling, & A.I.

What hormone released from the fetal adrenal cortex initiates parturition (birth)?

Cortisol

During parturition, which hormone declines while estrogen, prostaglandin, and oxytocin rise?

Progesterone

What hormone helps to relax cartilage and ligaments in the pelvic region during birth?

Relaxin

What are the common causes of dystocia (difficult birth)?

Females that are too young, abnormal presentations, an abnormally small pelvis, and a fetus that is too large

What is the inestrus interval and estrus duration for cattle?

Inestrus interval is 21 days; estrus duration is 12 hours (with ovulation occurring 10-18 hours after the end of estrus)

What is the inestrus interval and estrus duration for sheep?

Inestrus interval is 17 days; estrus duration is 24-36 hours (with ovulation occurring 18-24 hours after the end of estrus)

What is the inestrus interval and estrus duration for swine?

Inestrus interval is 21 days; estrus duration is 48-54 hours (with ovulation occurring 30-36 hours after the end of estrus)

What is the inestrus interval and estrus duration for horses (mares)?

Inestrus interval is 21 days; estrus duration is 6 days (with ovulation lasting during the last 2 days of estrus)

Which hormones surge together, peaking near estrus and GnRH release in a cow's estrous cycle?

Estradiol and LH

When do progesterone levels rise significantly during a cow or ewe's estrous cycle?

During diestrus / the luteal phase (mid-cycle, days 4-14)

What causes progesterone levels to drop rapidly around Day 14-15 in a ewe, triggering the next estrus/LH surge?

The drop in progesterone levels is caused by luteolysis, primarily due to the release of prostaglandin F2α from the uterus, which leads to the regression of the corpus luteum.

What are the primary objectives for synchronizing estrus?

Scheduled calving, more heats per breeding season, identifying problem cows, and facilitating the use of artificial intelligence (A.I.)

What is the "Ram Effect"?

A natural synchronization method in small ruminants where the sight, smell, and activity of introduced males stimulate an LH surge in females

What are the three main categories of synchronization methods/agents used in management?

Gonadotropins, Prostaglandins, and Progestins

What is the primary function of Gonadotropins (such as GnRH / Cystorelin) in estrous synchronization?

They stimulate the anterior pituitary to promote ovulation

How do Prostaglandins (PGF2alpha) work in estrous synchronization?

They shorten the current estrous cycle by causing the regression of the corpus luteum (luteolysis), but they only work on cycling females that have a CL present

What are examples of progestin delivery methods used to keep animals at the same state until removal?

CIDR vaginal insert and MGA feed supplement

What are common signs of estrus in females?

Standing to be mounted by other animals, persistent trailing or licking of other animals, nervous and restless behavior, a red and swollen vulva, mounting other animals, and clear (non-bloody) mucus discharge

What are examples of estrus detection aids used in livestock management?

Computer sensors, K-Mar, Bovine Beacon, Estrus Alert, paint sticks, gomer bulls, and pedometers

What is the primary advantage of Artificial Insemination (A.I.) regarding superior sires?

It permits a more extensive use of outstanding sires, which can produce up to 1,000 units (straws) of semen per week

What method of artificial insemination is used for cows?

Rectocervical insemination (manipulation of the cervix over the insemination gun via the rectum)

What is the "AM/PM Rule" for cattle insemination?

Cows detected in estrus in the morning are bred that same afternoon, and those found in estrus in the afternoon are bred the next morning

How is artificial insemination performed in sows?

Cervical insemination using a spirette with a counter-clockwise rotation into the cervix (gilts are inseminated 12 hours after detection, and sows at 24 hours)

How is artificial insemination performed in sheep, goats, and deer?

Laparoscopy (surgical introduction of semen directly into the uterine horns)

What instrument is used during goat artificial insemination to visually inspect the cervix?

A speculum (a tube-like instrument spanning the vulva and posterior vagina)

Which poultry species relies exclusively on artificial insemination to reproduce?

Commercially produced turkeys

What device is typically used to collect semen from bulls, stallions, and rams?

artificial vaginas

What is electro-ejaculation used for?

Stimulating nerves over the bulbourethral gland (Cowper's gland) to collect semen

What components make up a semen "extender" solution?

Fructose (energy source), double-distilled water (main volume), antibiotics (bacterial control), glycerol (prevents ice crystals during freezing), and egg yolk (nutrition and elasticity, often replaced by soy oil or milk-based products)

What is Embryo Transfer (ET)?

The movement of pre-implantation embryos from the reproductive tract of the genetic mother (donor) to the surrogate mother (recipient)

Who performed the first mammalian embryo transfer, and in what year?

Walter Heape in 1890 using rabbits

What hormone is used to induce super-ovulation in most donor species over a 4-day treatment window?

FSH (Follicle Stimulating Hormone)

When should bovine embryos ideally be collected post-estrus?

7 days post-estrus (with a range of 6-8 days)

What is administered to a donor cow prior to embryo collection to prevent rectal contractions?

An epidural block

What catheter is inserted through the vagina and cervix into the uterine horn during embryo collection?

A Foley catheter

What solution is used to flush embryos out of the donor's uterus?

A phosphate-buffered saline (PBS) solution enriched with calf serum and an antibiotic/antimycotic (1%)

When depositing an embryo into a recipient, where must the technician place it?

In the same uterine horn (same side of the uterus) as ovulation occurred in the donor female, as indicated by a mature corpus luteum