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Ott Troy (20)
Lecture 23

AN SC 431W Lecture 23: Lecture 23
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2 Pages
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Department
Animal Science
Course Code
AN SC 431W
Professor
Ott Troy

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ESTRUS/OVULATION SYNCHRONIZATION
1. Artificial insemination has had the biggest impact on genetic improvement in domestic
species
a. In order for AI to work, need to synchronize estrous cycles in female animals
2. “AM/PM Rule” if you see heat in the AM, breed in the PM. If you see heat in the PM,
breed in the AM
a. Heat precedes ovulation
b. A cow ovulates 28-30 hours after estrus (during metestrus)
c. Cow is in heat for 6-10 hours, so best to breed the following morning/night
3. Presynch: early method of estrus synchronization
a. 2 shots of prostaglandin (PG) 14 days apart to get all animals in luteal phase
i. Heat 72 hours after second shot
ii. Only works if corpus luteum is present
b. More cows in heat more heat you see. SAGS (sexually active groups) of
animals will mount each other, make heat detection easy
c. Presynch sets all animals up to same point in order to give Ovsynch shot of GnRH
i. Get cows between day 6-10 of cycle for Ovsynch
4. Ovsynch: later method to detect ovulation
a. Give GnRH shot
i. Cow releases surge of FSH/LH, gets cycle going
b. 7 days later, give shot of PG to kill corpus luteum
i. 48 hours later, shot of GnRH to cause pre-ovulatory LH surge
ii. 16 hours later, time artificial insemination
c. Ovsynch56 works best when GnRH shot given between day 6-10 of estrous cycle
i. Best conception rate
d. Breed, or “cherry-pick” any cows that come into heat before Ovsynch. Spares
them from receiving the rest of hormone shots
5. Presynch PG vs. Presynch PG/GnRH (Double Ovsynch)
a. Presynch with PG only effective if cow is already cycling and has formed CL
i. Tries to synchronize estrus
b. Presynch with PG and GnRH, otherwise known as Double Ovsynch, gets
everyone kick-started on cycle with preliminary shot of GnRH, then kills all CL
i. Used for breeding at Penn State
SPERMATOGENESIS
1. Germ cells (2n) in basal compartment
a. Undergo mitosis to increase number of cells
2. Primary spermatocytes (2n)
a. Undergo meiosis I to produce secondary spermatocytes
3. Secondary spermatocytes (n)
a. Undergo meiosis II to become spermatids
4. Spermatids develop into mature spermatozoa
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Description
ESTRUS/OVULATION SYNCHRONIZATION 1. Artificial insemination has had the biggest impact on genetic improvement in domestic species a. In order for AI to work, need to synchronize estrous cycles in female animals 2. “AM/PM Rule” if you see heat in the AM, breed in the PM. If you see heat in the PM, breed in the AM a. Heat precedes ovulation b. A cow ovulates 28-30 hours after estrus (during metestrus) c. Cow is in heat for 6-10 hours, so best to breed the following morning/night 3. Presynch: early method of estrus synchronization a. 2 shots of prostaglandin (PG) 14 days apart to get all animals in luteal phase a.i. Heat 72 hours after second shot a.ii. Only works if corpus luteum is present b. More cows in heat  more heat you see. SAGS (sexually active groups) of animals will mount each other, make heat detection easy c. Presynch sets all animals up to same point in order to give Ovsynch shot of GnRH c.i. Get cows between day 6-10 of cycle for Ovsynch 4. Ovsynch: later method to detect ovulation a. Give GnRH shot a.i. Cow releases surge of FSH/LH, gets cycle going b. 7 days later, give shot of PG to kill corpus luteum b.i. 48 hours later, shot of GnRH to cause pre-ovulatory LH surge b.ii. 16 hours later, time artificial insemination c. Ovsy
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