Equine seasonality Flashcards
Ovaries
Free border/ OV fossa (site of OV)
Surrounded by tunic
Follicles palpated on surface
Average growth rate of a dominant follicle
5-6 mm/day
Cues that OV occured
Uterine tone ↑
Cervix closes
Receptive behavior changes from progesterone
_________ is the major factor determining activity or inactivity of the mare’s reproductive system
Daylength
Kisspeptin
Protein released by presyn. neurons, bind to receptors on GnRH secreting neurons
Prereq. for onsite of puberty
Impacts pineal gland
Pineal gland
Controls repro. in seasonal breeding species and in time of puberty by influencing FSH, LH and prolactin release
Melatonin
Relationship of pineal gland melatonin concentration to hypothalamic activity =↑ or ↓ GnRH
Seasonality
Daylength → pineal gland → hypothalamus → anterior pituitary
Vernal equinox (spring)
Melatonin ↓, GnRH ↑ and anterior pituitary releases FSH and LH
daylight hours ↑
Autumnal Equinox
Melatonin ↑, GnRH ↓ and anterior pituitary release of FSH and LH ↓
Puberty in a female quid
@ 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
Estradiol threshold reached
Stimulates preovulatory surge of GnRH → preovulatory surge in LH, OV, and the initiation of puberty
Seasonal shifts
30-60 days of altered light duration required to stimulate the shift from one season to the next
Predominant gonadal hormones in vernal transition
FSH results in 3 waves of follicular development
↑ ovarian activity
Dominant follicules produce estradiol
Follicles in the 3rd wave are _________
Steroidogenic
Determining mares progress to OV period
Regular teasing program**
Transrectal palp
Hormonal assays/ manipulation of estrous cycle
Teasing programs
Mares to stallion or vice versa
Pony stallions
Frequent and thorough evaluations
When are teasing programs done?
Begin 1 month prior to anticipated onset breeding
Daily or every other day**
Operational breeding season (OBS)
Beings Feb 15th, teasing should begin mid-january
The mare’s estrous cycle is _______
21 days
Shifts within the estrous cycle
With each cycle, duration of estrus ↓ from early in the oBS to physiological breeding season (PBS)
OBS: 8-10 dys + , PBS: 4 dys
Teasing program guidelines
Record first day of receptivity, length of receptivity and duration of diestrus
Continues throughout season, post breeding and dx of pregnancy
When does OV occur?
24-28 hrs prior to end of estrus
Vernal transition
Mare progresses from passive into extended to erratic periods of behavioral estrus
Duration: 30-60-90 + days
Transitional ovaries of the mare
Multiple, large, slow-growing follicles
Mare’s receptivity
Dominant follicle with estradiol (receptive)
CL present with progesterone (not)
Autumnal transition
Mare goes from periods of estrus and diestrus into extended or irregular behavioral estrus
Large persistent follicles
Transrectal palpation (winter anestrus)
Ovaries small and static
Uterus: poor tone
Cervix: Relaxed or partially close
Barren mares during winter anestrus
Barren mares with poor vulvar conformation should have a Caslick’s vulvoplasty to protect them from ascending contamination
Transrectal palpation (vernal transition)
Ovaries have multiple follicles
Uterus: poor tone (until OV)
Cervix: Relaxed or partially close (in %)
Transrectal palpation (estrus)
Ovaries: dominant follicle ↑ 5-6 mm a day
Uterus: ↑ tone
Cervix:Relaxes (shorter, wider, softening)
Uterus tone is a reflection of the presence of ________
Progesterone
Edema of endometrial folds
Present during estrus (luminal fluid abnormal)
↓ in the last hours leading to OV
