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Flashcards in Bovine Estrous Cycle Deck (53)
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1

When is puberty in cattle?

8-12mo

2

What is the seasonality of cattle reproduction?

Non-seasonal breeders

3

How long is the estrus cycle of a cow?

21d

4

Which hormone acts directly on a follicle to stimulate the growth of the follicles?

FSH

5

Which hormone causes ovulation of a mature follicle?

LH

6

What hormones does a follicle secrete?

Estrogen and inhibin

7

Which homone secreted by a follicle causes a positive feedback loop to the hypothalamus?

Estrogen

8

What does a CL produce?

Progesterone

9

What hormone maintains pregnancy?

Progesterone

10

How does progesterone affect the hypothalamic and pituitary hormones?

Negative feedback on LH

11

What hormone can destroy/lyse a CL?

Prostaglandins (PGF2a)

12

How many follicular waves does a cow have?

2-3 waves per cycle w/one dominant follicle per wave

13

When does the LH surge occur in relation to follicular waves?

LH surge w/last wave

14

What is the optimal breeding time for a cow?

Middle of estrus to 6h after end of estrus

15

How long after ovulation is an ovum fertilizable?

8-10h

16

What are indications for estrus synchronization in cows?

Increased mating efficiency, shortening of birthing season

17

What are techniques of estrogen synchronization?

P4, PGF2a, both, or GnRH + PGF

18

Which estrogen synchronization technique acts as an "artificial CL"?

Progesterone therapy

19

How does progesterone administration synchronize a cow?

Suppresses LH to prevent ovulation

20

How long do you have to give exogenous progesterone for synchronization to work?

10-14d

21

What device is used for progesterone therapy adminsitration?

CIDR

22

What is the protocos for prostaglandin estrous syncrhonization?

2 inj 14d apart

23

The first PGF injection causes luteolysis in what % of females?

50-60%

24

Which PGF injection syncrhonizes majority of the herd?

Second

25

What is the Ovsynch program?

GnRH + PGF

26

What is the goal of the first GnRH administration of the Ovsynch program?

Luteinization or ovulation of follicles

27

How soon after GnRH injection is PGF administered?

7d later

28

When is the second GnRH dose administered to a cow?

2d after PGF

29

What is the goal of the 2nd GnRH dose of the Ovsynch program?

Induce ovulation of the next follicle (at the same time as the rest of the herd)

30

How soon after the 2nd GnRH administration can you time AI?

24h after GnRH injection