Equine seasonality

Question 1

Ovaries

Answer 1

Free border/ OV fossa (site of OV)
Surrounded by tunic
Follicles palpated on surface

Question 2

Average growth rate of a dominant follicle

Answer 2

5-6 mm/day

Question 3

Cues that OV occured

Answer 3

Uterine tone ↑
Cervix closes
Receptive behavior changes from progesterone

Question 4

_________ is the major factor determining activity or inactivity of the mare’s reproductive system

Answer 4

Daylength

Question 5

Kisspeptin

Answer 5

Protein released by presyn. neurons, bind to receptors on GnRH secreting neurons
Prereq. for onsite of puberty
Impacts pineal gland

Question 6

Pineal gland

Answer 6

Controls repro. in seasonal breeding species and in time of puberty by influencing FSH, LH and prolactin release

Question 7

Melatonin

Answer 7

Relationship of pineal gland melatonin concentration to hypothalamic activity =↑ or ↓ GnRH

Question 8

Seasonality

Answer 8

Daylength → pineal gland → hypothalamus → anterior pituitary

Question 9

Vernal equinox (spring)

Answer 9

Melatonin ↓, GnRH ↑ and anterior pituitary releases FSH and LH
daylight hours ↑

Question 10

Autumnal Equinox

Answer 10

Melatonin ↑, GnRH ↓ and anterior pituitary release of FSH and LH ↓

Question 11

Puberty in a female quid

Answer 11

@ 1-2 years
Transition to puberty starts → sensitivity of hypothalamic surge center to estradiol inhibition ↓ → hypothalamic neurons secrete GnRH → LH and FSH ↑ → ovary stimulates and produces more estradiol

Question 12

Estradiol threshold reached

Answer 12

Stimulates preovulatory surge of GnRH → preovulatory surge in LH, OV, and the initiation of puberty

Question 13

Seasonal shifts

Answer 13

30-60 days of altered light duration required to stimulate the shift from one season to the next

Question 14

Predominant gonadal hormones in vernal transition

Answer 14

FSH results in 3 waves of follicular development
↑ ovarian activity
Dominant follicules produce estradiol

Question 15

Follicles in the 3rd wave are _________

Answer 15

Steroidogenic

Question 16

Determining mares progress to OV period

Answer 16

Regular teasing program**
Transrectal palp
Hormonal assays/ manipulation of estrous cycle

Question 17

Teasing programs

Answer 17

Mares to stallion or vice versa
Pony stallions
Frequent and thorough evaluations

Question 18

When are teasing programs done?

Answer 18

Begin 1 month prior to anticipated onset breeding
Daily or every other day**

Question 19

Operational breeding season (OBS)

Answer 19

Beings Feb 15th, teasing should begin mid-january

Question 20

The mare’s estrous cycle is _______

Answer 20

21 days

Question 21

Shifts within the estrous cycle

Answer 21

With each cycle, duration of estrus ↓ from early in the oBS to physiological breeding season (PBS)
OBS: 8-10 dys + , PBS: 4 dys

Question 22

Teasing program guidelines

Answer 22

Record first day of receptivity, length of receptivity and duration of diestrus
Continues throughout season, post breeding and dx of pregnancy

Question 23

When does OV occur?

Answer 23

24-28 hrs prior to end of estrus

Question 24

Vernal transition

Answer 24

Mare progresses from passive into extended to erratic periods of behavioral estrus
Duration: 30-60-90 + days

Question 25

Transitional ovaries of the mare

Answer 25

Multiple, large, slow-growing follicles

Question 26

Mare’s receptivity

Answer 26

Dominant follicle with estradiol (receptive)
CL present with progesterone (not)

Question 27

Autumnal transition

Answer 27

Mare goes from periods of estrus and diestrus into extended or irregular behavioral estrus
Large persistent follicles

Question 28

Transrectal palpation (winter anestrus)

Answer 28

Ovaries small and static
Uterus: poor tone
Cervix: Relaxed or partially close

Question 29

Barren mares during winter anestrus

Answer 29

Barren mares with poor vulvar conformation should have a Caslick’s vulvoplasty to protect them from ascending contamination

Question 30

Transrectal palpation (vernal transition)

Answer 30

Ovaries have multiple follicles
Uterus: poor tone (until OV)
Cervix: Relaxed or partially close (in %)

Question 31

Transrectal palpation (estrus)

Answer 31

Ovaries: dominant follicle ↑ 5-6 mm a day
Uterus: ↑ tone
Cervix:Relaxes (shorter, wider, softening)

Question 32

Uterus tone is a reflection of the presence of ________

Answer 32

Progesterone

Question 33

Edema of endometrial folds

Answer 33

Present during estrus (luminal fluid abnormal)
↓ in the last hours leading to OV