Lecture 6: Female Reproductive Physiology: Factors modulating female cyclicity Flashcards
What is puerperium
Uterine recovery time
Mares have a ___puerperium and therefore ___probability of conception at the first postpartum estrus
Short, good
what is gestation period for horses
330-345
When does the estrus cycle start after foaling
5-8 days after foaling
When does ovulation occur after foaling
10 days
To breed horses yearly, breeders must take advantage of ____
Foal heat
What happens if you breed mare on 2nd heat
Mare will eventually miss a year of breeding when the season comes too late
Foal heat: ___ + ___
345 +7= 352 < a year
2nd heat= ___ + ___
345 +28= 373 > a year
What regulates female reproduction cyclicity
Hypothalamus
What are the external modulators factors that influence the timing of cyclicity in the female
Photoperiod/season
Lactation
Social factors/phermones
Nutrition
Age
What is polyestrous and what species fall under this category
Year round breeders
Cow, sow, humans
What is seasonally polyestrous and what species fall under this category
Several estrous cycles followed by an anestrous
Horse, cat, sheep, goat
What is monoestrous and what species fall under this category
One estrous cycle followed by a prolonged anestrous
Dog, wolf, bear
Anestrous is characterized by low ___ release and low ____ activity
Low estrogen and reproductive activity
What are long day breeders and what species fall under this category
Breed when days get longer
Mares and queens
When do mares typically breed
March-October
When do queens typically breed
January-October
What are short day breeders and what species fall under this category
Breed when days get shorter
Sheep, goats, dear, and elk
When do sheep and goats typically breed
July-February
__is the primary controller of reproductive cycles
Light
___sensitives the HPG axis by releasing GnRH
Light
What are some other factors besides light that trigger the HPG axis
Sexual stimuli- phermones, sound, visual
In females ___is the main modulator of female ovarian cycle
Light
What additional factors influence the female ovarian cycle
Lactation, nutrition, social condition, age
The pineal gland releases ___in response to darkness
Melatonin
Light stimulates the retina and activates _____ through ____ tract
Hypothalamic suprachiasmastic nucelus (SCN) through the retinal hypothalamic tract
What inhibits the pineal gland to decrease melatonin
SCN
SCN inhibits the pineal gland to decrease melatonin to alter the timing of what 2 things
- Day-night activity
- Seasonal breeding activity
Describe the role of light in reproductive timing of long day breeders
- Melatonin excites RFamide-related peptide (RFRP-3) neurons
- RFRP-3 neurons activate kisspeptin in hypothalamus
- Kisspeptin stimulates GnRH neurons
Describe the role of light in reproductive timing of short day breeders
- Melatonin excites RFamide-related peptide 3 (RFRP-3) neurons
- RFRP-3 neurons inhibit kisspeptin
- Therefore, inhibiting release of GnRH
Clinical Correlation: Mare on foal heat day 7, was not bred, 40 days have passed and no estrus, no response to teasing by stallion.
Small, constricted cervix with considerable tone but quiescent, normal ovaries, one with large 35mm follicles
What is likely cause?
What test can be run?
Treatment?
Persistent corpus luteum, follicles > 30mm
Test: serum progesterone 1-2 ng/mL (peak cycle progesterone= 3 ng/mL)
Treatment: administer PGF2alpha monitor for estrus in 5-7 days
Clinical correlation: foal heat 7 days after birth, was not bed, 40 days have passed and no estrus, no response to teasing by stallion.
Small cervix that is not closed or tight. Uterus is small and flaccid, inactive ovaries with no follicles > 10mm
What is the likely cause?
Test?
Treatments?
Mare is in anestrus, mares that foal early can be adversely affected by the short photoperiod and become anestrus
Test: serum estrogen and progesterone= low
Treatment #1: artificial manipulation of photoperiod
Treatment #2: breed on the foal heat to avoid the odds that the mare foaling early in the year will re-enter anestrus during the foal heat ovulation
How does phototrophic stimulation in mares work
Artificial lighting provided for ~60 days can induce early breeding
Stimulates return to estrus
How does seasonality affect age and puberty ex: lambs
Spring born lambs come into puberty at a younger age than their fall born flock mates
Due to increase day length
Do gilts in small or large herds enter puberty later
Gilts in small herds enter later than in large groups
Gilts exposed to a boar even in small groups will reach puberty ____
Earlier
How does lactation affect ovulation in sows
Complete inhibition of ovulation
How does lactation affect ovulation in cats, beef cows, primates
Partial suppression of ovulation
Suckling inhibits ___ which releases ___
Dopamine, prolactin
When dopamine is suppressed, lactrotrophs release prolactin, prolactin inhibits ____ synthesis
GnRH
Describe the suckling/lactaiton signaling
- Stimulus from suckling signals to hypothalamus
- Inhibit dopamine release from arcurate nucleus
- Decreased dopamine release removes inhibition that is usually put on lactrotrophs in anterior pituitary, leading to prolactin release
- Prolactin stimulates milk production in the breast
- Oxytocin is also released from PVN and SON. Travels to breast and myoepithelial cells
- Neurons inhibit arcurate and preoptic area, these decreasing GNRH production.
- Reduced stimulation of gonadotrophs inhibits ovarian cycle
Suckling in cows: when the number of suckling sessions is between 3-20/day the amplitude and pulse frequency of blood ___ are low and cow remains in ____
LH, anestrus
Suckling in cows: when the number of suckling sessions is limited to two or less per day the amplitude and pulse frequency of ___ increases and cow will begin to cycle
LH
How does body weight effect ovulation
Low body weight can delay ovulation to end of winter
____ body weight and percent fat are associated with greater reproductive activity
Higher
Animals with better body composition can achieve a ____ pregnancy rate
Higher
What do insulin and leptin do to appetite
Suppress
What does gherlin do to appetite
Stimulate
What hormone signals steroidogenesis
growth hormone-IGF-1
What hormone induces steroidogenesis
Thyroid hormone
Blood glucose levels are detected in the ___
Hypothalamus
Leptin is released by ___ in response to increase in ___ volume
Adipocytes and adipocyte
Release of leptin is proportional to the amount of ___
Energy stored
Leptin targets __ neurons in hypothalamus
Kisspeptin
Leptin targeting kisspeptin neurons in hypothalamus affects release of ____ from the ____
GnRH from the preoptic nucleus
Fasting in heifers is associated with ___leptin and ___LH pulse frequency
Low leptin and lower LH pulse frequency
Food deprived mice show ___estrus which is reversible by ___ treatment
Delayed estrus, leptin treatment
Leptin experimentally administered to young mice ____entry to puberty
Accelerates
___ stimulates pro-opiomelanocortin (POMC) neurons in the arcurate nucleus
Leptin
POMC neurons regulate…
Appetite, metabolism and body weight
What does 2-deoxyglucose (2-DG) experimentally induce
Starvation
What happens to LH levels in sheep after administered 2-DG
LH disappears
To maintain a yearly calving interval, cows must become pregnant by ___ days after calving
80-85 days
In first lactation trimester, energy requirement for milk productions ____ energy intake
Exceeds
Milk production in cows peaks at weeks ___
4-6
Feed intake in lactating cows peaks at weeks ___
9-11
What is flushing
Management term for providing high quality feeds, usually grains prior to the start of the breeding to increase reproductive performance
Increase in energy and/or protein will ___ incidence of ovulation
Increase
Increase in energy and/or protein intake can produce and release multiple ___ in small ruminants and sows
Eggs
How is fertility reduced in old age
Reduced follicle number, cessation of live births, irregular cycles, increased cycle length, increased inter birth interval
Ovarian exhaustion of the follicle is ___ of reproductive senescence
Pacemaker
How are estrogen, gonadotropin/LH and FSH levels affected in older females
Reduced estrogen
LH levels insufficient to trigger ovulation
Elevated FSH due to fever follicles
During old age is the estrus cycle shorter or longer
Shorter