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Flashcards in Equine Estrous Cycle Deck (38)
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1

What type of breeders are horses?

Seasonal polyestrus (April-Oct)

2

What day length is required for horse breeding?

Long-day breeders (April-Oct)

3

When is a horse's transition period of follicular growth and regression?

Spring

4

How long is an estrous cycle in horses?

19-26d

5

How many follicular waves do horses have?

One (can be major or minor) that repeatedly grows and regresses until ovulation

6

What hormone is high during estrus?

Estrogen

7

How long is estrus in a horse?

5-7d

8

When does a horse ovulate?

1-2d prior to end of estrus

9

What are breeding options for horses?

EOD starting on 2nd day of estrus or 24-48h prior to ovulation

10

How long is diestrus in a horse?

14-16 days

11

Is there a metestrus in a horse?

No

12

How do you synchronize mares?

PGF2a and progestins

13

What age of CL does PGF2a work on?

CL >5d and mare in diestrus

14

How does a PGF2a dose for a horse compare to that for a cow?

Lower dose, more side effects

15

When does ovulation occur after PGF2a administration?

8-9d

16

What is the purpose of mare synchronization?

AI/embryo transfer, failure of CL to regress/prolonged diestrus

17

What are oral progestins used in mares?

Regumate

18

What is a non-reproductive purpose of progestin use in mares?

Suppress estrus in performance mares

19

How can you induce ovulation in anestrus mares?

Increase light exposure (16h/d) for 30-60d

20

How soon after foaling do mares return to estrus?

10d

21

What is the most effective way to restart cycling or get horses to start cycling early?

Artificial light (16h/d) for 30-60d

22

What is gestation length in a horse?

345d

23

When is a foal considered premature?

Born prior to 320d gestation

24

When do most horse owners want their mares to foal?

Mid-January (breed mid-Feb)

25

What maintains pregnancy in a horse?

Ovarian P4 early, placental P4 later

26

What begins stage 1 of parturition?

Fetal repositioning for parturition

27

What begins stage 2 of parturition?

Rupture of chorioallantois

28

What ends stage 2 of parturition?

Birth of foal

29

What is stage 3 of parturition?

Passage of placenta

30

When is a placenta considered retained?

After 3 hours