LA THERIO - Estrous Synchronization

Question 1

Name the molecules of prostaglandin F2a or its analogue that are approved for use in cattle in the United States.

Answer 1

Natural: dinoprost tromethamine
Synthetic: Cloprostenol

Question 2

What hormonal events occur when you administer the following hormones:

A. PGF2a or analogues
B. GnRH

Answer 2

GnRH → cows with mature follicles will: ovulate or leutenize
GnRH → cows that don’t have anything will recruit follicles.
**GnrRH comes from hypothalamus → stimulates FSH and LH release. Give GnRH if you want to induce ovulation or follicular growth.

Progesterone: comes from CL
Progesterone function: inhibit LH surge, maintain pregnancy
indications for progesterone: synchronization of follicular waves.
forms: CIDR, MEgestrol acetate

PGF2alfa released by endometrium
PGF2alfa indications: Luteolysis

Question 3

What is the main action of a CIDR?

Answer 3

CIDR (Controlled internal drug release dispenser) provides 7 days of progesterone
provides enough negative feedback on LH
regulates all follicular waves

Question 4

When would you observe estrus in cows after administration of a luteolytic dose of PGF2a or its analogue during diestrus?

Answer 4

2-5 days later

Question 5

What hormones are used for ovulation synchronization in the Ovsynch program, and what is their action?

Answer 5

Question 6

Why is timed artificial insemination (fixed-time) used in dairy cattle?

Answer 6

Improved synchrony

Improves response in
- Anovular cows
- Anestrus
- Cystic ovarian disease