Theriogenology - Equine

Front 1

what does puberty mark?

Back 1

ability to release gametes, not necessarily fertile

Front 2

when do horses reach puberty?

Back 2

15-18mo, depending on time of year, related to body weight, season, breed, others, with sexual maturity occuring at ~4yrs, limited fertility is associated with the onset, caused by an increase in GnRH pulse generator activity (high frequency, high amplitude)

Front 3

basics of equine estrous cycle

Back 3

long-day breeders, seasonally polyestrous (85% seasonally polyestrous, 10% irregularly poyestrous, 5% polyestrous)

Front 4

describe equine estrous cycle?

Back 4

proestrus, estrus, diestrus

Front 5

describe proestrus

Back 5

proestrus (12-48h before behavioral estrus, decreasing/low progesterone, passive teasing, moderate cervical tone, uterine edema on palpation an enlarged uterus, with typical patter on US)-sliced orange pattern, more variable, especially at transition

Front 6

describe estrus

Back 6

behavior estrus (urinates, winks, etc), 5-7d (variable), ends 24-48h post ovulation, absence of well-define LH surge, estrus may be shorter during late summer, cervix relaxes (soft on palpation, edema on US, vaginal speculum open, moist, edematous, pink, low), uterus (enlarged and soft on palpation, US edema), follicular dynamics (1-2 follicular waves, ~20% double ovulation, diestrus ovulation)

Front 7

describe diestrus

Back 7

most predictable, P4 production by the corpus luteum (CL), teasing squeals, pins ears, etc, very consistent stage of the cycle (14-15d from end of behavioral estrus or 15-16 day from ovulation day), cervix tightens up (tubular, dry, pale, high position in relation to the vaginal floor)

Front 8

maternal recognition of equine pregnancy

Back 8

we don’t know', possibly embryonic E2 production, CL is needed, uterine proteins

Front 9

endocrinology of parturition

Back 9

E2:P4 increases 24h before foaling (but isn't predictive), relaxin increases, prostaglandins increase, followed by oxytocin

Front 10

equine purturition stages

Back 10

stage 1 (hard to id, ~4h, when premature placental seperation-red bag- may occur), stage 2 (rupture chorioallantoic membrane, averages 20min, rarely >60m), stage III (placenta is passed withn 0.5-3h)

Front 11

equine postpartum

Back 11

before foaling fetal gonads are larger than dam's ovaries, first estrus (Foal heat) >> 7-10 d postpartum (normal fertility if well managed)

Front 12

stallion physiology

Back 12

complex event that involves interactions between: pineal gland, hypothalamus, pituitary gland, testis: effects of daylight are not as pronounced as in the mare, but still occur, may affect testicular size, libido, semen production, hormone concentrations