Repro Physiology

Question 1

What is the first sign of pregnancy for palpation?

Answer 1

Bulge on the ventral aspect of the horn

Question 2

What is responsible for triggering ovulation?

Answer 2

LH

Question 3

What suppresses LH?

Answer 3

Progesterone

Question 4

Puberty occurs around ______

Answer 4

2 years of age

Question 5

Polyestrus

Answer 5

Long day breeders

• northern hemisphere: spring/summer
• southern hemisphere: fall/winter
• cycle from March-October (20% will cycle year round)

Question 6

Mare will ______ during the breeding season

Answer 6

Repeatedly cycle

- recurring estrus on a predictable interval until pregnant or season ends

Question 7

Estrous cycle

Answer 7

From ovulation to subsequent ovulation

Question 8

Follicular phase

Answer 8

Estrus

• estrogen is dominant
• estrus ends 18-24 hrs after ovulation

Question 9

Luteal phase

Answer 9

Diestrus

- starts with ovulation until luteolysis

Question 10

Ovulation to ovulation is ______

Answer 10

21 days

Question 11

Estrus

Answer 11

Behavioral signs associated with impending ovulation

• receptivity to male
• occurs when progesterone is low (after luteolysis)

Question 12

Give _____ if you do not want a mare to show estrus signs

Answer 12

Progesterone

Question 13

Jump mare

Answer 13

Mare that has had her ovaries removed, so progesterone levels are nonexistent

• will be passive whenever a stallion is presented
• can collect stallions whenever needed

Question 14

Entire estrous cycle lasts

Answer 14

20-24 days

Question 15

Estrus lasts

Answer 15

4-7 days

• single follicular wave is most common in equines
• cows have 2-4 waves
• dominant hormone is estrogen

Question 16

Follicular wave

Answer 16

Cohort of immature primordial follicles that emerge until 1 becomes dominant and suppresses all others

Question 17

Diestrus lasts

Answer 17

14-15 days

• consistent length in equines
• dominant hormone is progesterone

Question 18

Mares ovulate _______ before going out of heat or estrus

Answer 18

24-48 hrs

Question 19

Ovulation

Answer 19

Occurs prior to the end of estrus

• follicle size at ovulation is generally 40-45 mm
• size can be breed dependent
• double ovulation occur 16% (twinning)

Question 20

______ follows ovulation

Answer 20

Luteal phase

Question 21

Mares ovulate_____, toward the ______

Answer 21

Inward; ovulation fossa

Question 22

Predicting ovulation

Answer 22

Used for breeding purposes

• follicles grow 3-4 mm per day
• follicle becomes soft
• loss of spherical shape with development of apex
• serrations in granulosa layer

Question 23

Teasing with stallion - estrus

Answer 23

• tail raise
• squat, tip pelvis
• urinate
• evert clitoris

Question 24

Exam of ovaries - estrus

Answer 24

• large follicle, may be soft
• follicle may be triangular w/ scalloped edges on US if mare is near ovulation
• no CL on US

Question 25

Exam of uterus - estrus

Answer 25

- relaxed w/ soft texture | - edematous endometrial folds visible on US

Question 26

Exam of cervix - estrus

Answer 26

- shortening, widening - relaxed w/ soft texture - pink and drooping on vaginal floor - lumen open 1-3 fingers on digital exam per vagina

Question 27

Teasing w/ stallion - diestrus

Answer 27

- switch tail - kick, squeal - attempt to bite - move away

Question 28

Exam of ovaries - diestrus

Answer 28

- presence of CL on US | - follicles of varying sizes, may be large

Question 29

Exam of uterus - diestrus

Answer 29

- firm texture (good tone) | - uniform echogenicity on US

Question 30

Exam of cervix - diestrus

Answer 30

- long and narrow, firm texture - pale, dry, centrally located in cranial vagina - closed lumen on digital exam

Question 31

Seasonality in mares is regulated by ______

Answer 31

Photoperiod - improved efficiency during periods of increased daylight - length of photoperiod modulates GnRH secretion

Question 32

During short days, _____ secretes ______

Answer 32

Pineal gland; melatonin | - suppresses GnRH

Question 33

During long days ______

Answer 33

Little melatonin is released, suppression is removed

Question 34

Melatonin

Answer 34

Released when it is dark! - inhibitory effect on GnRH in the mare - secreted by pineal gland, under control by retina's detection of light via photoreceptors

Question 35

Melatonin's effects

Answer 35

- short days: pineal gland secretes more melatonin so GnRH is inhibited (anestrus) - long days: pineal gland releases little melatonin and GnRH is not inhibited (mare cycle's)

Question 36

Vernal transition

Answer 36

Period of time during spring and fall when mare is transitioning from anestrus to cyclicity and reverse in the fall - ambiguous signs of estrus seen - ends w/ first ovulation of the season

Question 37

Spring transition

Answer 37

- erratic estrus behavior - erratic follicular growth - anovulation - improper breedings

Question 38

Stallion repro physiology

Answer 38

Puberty at 2 years | - seasonal pattern of sperm production is evident, but they never stop producing

Question 39

_____ is the physiological breeding season for horses

Answer 39

April-Sept | - best fertility in May-July

Question 40

_____ is autumn transition

Answer 40

Oct-Nov | - going out of season

Question 41

______ is winter anestrus

Answer 41

Dec-Jan - no signs of estrus - little to no follicular activity

Question 42

_____ is spring transition

Answer 42

Feb-March | - coming into season

Question 43

Imposed breeding season

Answer 43

Jockey club states that all foals are 1 year of age on Jan 1st - larger foals top the sales - breeders want to have the largest foals - pushed to breed mares when environmental cues say they shouldn't

Question 44

Lighting schemes

Answer 44

Place mares under lights beginning Dec 1st (16 hrs daily) - continue for 60 days - photoperiod is manipulated - mares enter vernal transition sooner --> first ovulation sooner

Question 45

Foal heat

Answer 45

First postpartum estrus - occurs around 10 days postpartum - fertility is adequate in most cases

Question 46

Backing up a mare

Answer 46

Have her foal earlier in subsequent years than the current year - gestation length of approx 340 days - to keep her around the same foaling date, she would need to conceive within 25 days of foaling