animal science 434 reproductive cyclicity in the female
TRANSCRIPT
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Animal Science 434
Reproductive Cyclicity in the Female
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Terminology
• Estrus is a noun.– The cow is displaying estrus.
• Estrous is an adjective.– The length of the estrous cycle is 21
days.
• Oestrus and Oestrous– British and European spellings
• Estrus and Heat are synonymous
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Terminology (cont.)
• Anestrus –When the female is not having repeated
estrous cycles.
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Types of Cyclicity
PolyestrusPolyestrus
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Types of Cyclicity
Seasonally PolyestrusSeasonally Polyestrus
Short day breeders
(Fall)
Long day breeders
(Spring)
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Type of Cyclicity
MonoestrusMonoestrus
Dog Wolf Bear
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Average Reproductive CyclesSpecies Length of Length of Ovulation Length of
Estrous Cycle Estrus Pregnancy
cow 21 days 18 hr 11 hr after 282 days polyestrus end estrus
ewe 17 days 29 hr near end 148 daysseasonal (fall) estrus
sow 21 days 48-72 hr 35-45 hr 115 days polyestrus after start
estrus
mare 21 days 4-8 days 3-6 day of 335 daysseasonal (spring) estrus polyestrus (1-2 days
before end ofestrus)
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Variation in Cycle Types
Example Type of Follicular Ovulation & CL Cycle Development CL Formation
Function
Cow, ewe, Long Spontaneous SpontaneousSpontaneous
sow, mare
rats, mice, Short Spontaneous Spontaneous Inducedhamsters (4 days)
(prolactin)
rabbit, cat, Induced Spontaneous Induced Inducedmink, ferret, (LH surge)otter, alpaca
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AtresiaCLCAOvulationCLDays Relative to the Gonadotropin Surge012345678-1- 2- 3- 4- 5- 6-7LHFSHPGF2αEstradiolProgesteroneMetestrusDiestrusProestrusDiestrusEstrus
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AtresiaCLCAOvulationCLDays Relative to the Gonadotropin Surge012345678-1- 2- 3- 4- 5- 6-7LHFSHPGF2αEstradiolProgesteroneMetestrusDiestrusProestrusDiestrusEstrus
Follicular PhaseProestrus• follicle enlarges
• estrogen increases
• vascularity of the female reproductive tract increases
• endometrial glands begin to grow
• estrogen levels peak
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Estrus• allows male to mount
• estrogen decreases
• LH surge occurs
• ovulation 24-48 hr after surge of LH
• uterine motility high with contractions moving toward oviduct
• sperm transport is optimal
• cervical mucus volume increases
AtresiaCLCAOvulationCLDays Relative to the Gonadotropin Surge012345678-1- 2- 3- 4- 5- 6-7LHFSHPGF2αEstradiolProgesteroneMetestrusDiestrusProestrusDiestrusEstrus
Follicular Phase
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AtresiaCLCAOvulationCLDays Relative to the Gonadotropin Surge012345678-1- 2- 3- 4- 5- 6-7LHFSHPGF2αEstradiolProgesteroneMetestrusDiestrusProestrusDiestrusEstrus
Luteal PhaseLuteal Phase
Metestrus• estrogen low
• ovulation in cow
• corpus hemorrhagicum present
• uterus
contractions subside
endometrial glands continue to grow and become coiled
in cattle bleeding occurs
• FSH increases
triggering growth of follicles
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AtresiaCLCAOvulationCLDays Relative to the Gonadotropin Surge012345678-1- 2- 3- 4- 5- 6-7LHFSHPGF2αEstradiolProgesteroneMetestrusDiestrusProestrusDiestrusEstrus
Luteal PhaseLuteal Phase
Diestrus• progesterone high
• FSH
Increases at some point to cause growth of ovulatory follicle
•Uterus
secrets fluid but volume gradually decreases
contraction stop
CL regresses at the end of this period if female is not pregnant due to PGF release
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Characteristics of Estrous CyclesCharacteristics of Estrous Cycles
Cow Ewe Sow Mare
Estrous cycle (days) 21 17 21 21
Proestrus (days) 3-4 2-3 3-4 2-3
Estrus 12-18 hr 24-36 hr 48-72 hr 4-8 days
Metestrus (days) 3-4 2-3 2-3 2-3
Diestrus (days) 10-14 10-12 11-13 10-12
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Causes of Anestrus
Pregnancy Presence of Offspring
Season
Stress
Pathology
Nutrition
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Gestational AnestrusGestational Anestrus
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Gestational Anestrus
• Progesterone during pregnancy– negative feedback
• After parturition anestrus continues– progesterone exposure during
pregnancy– hypothalamus • Lacks estradiol positive feedback
• allows time for uterine involution
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Seasonal AnestrusSeasonal Anestrus
Horses are long day breeders!Horses are long day breeders!
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Sheep are short day breeders!
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EstradiolEstradiol
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NegativeFeedback
PositiveFeedback
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EstradiolEstradiol
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Seasonal Anestrus
• just like entering puberty
• silent ovulation
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++
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Silent Ovulation
Anestrus Estrus
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Lactational AnestrusLactational Anestrus
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Suckling Effect on LH
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Lactational Anestrus
• Suckling
• Other offspring factors– visual encounter– olfactory encounter– auditory encounter
• Prolactin– inhibits GnRH release–major infertility problem in women who
are not lactating
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Nutritional Anestrus
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Menstrual CycleMenstrual Cycle
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FSHLHLH
EstradiolEstradiol
ProgesteroneProgesterone
FollicleOvulation
Corpus LuteumCorpus
Albicans
2 4 6 8 10 14 16 18 20 22 24 26 28 212
Anterior Pituitary
Hormones
Ovarian Hormones
Ovary
UterineEndo-
metrium
RecruitmentSelectionDominance
Recruitment
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FSHLHLH
EstradiolEstradiol
ProgesteroneProgesterone
FollicleOvulation
Corpus Luteum
2 4 6 8 10 14 16 18 20 22 24 26 28 212
Anterior Pituitary
Hormones
Ovarian Hormones
Ovary
UterineEndo-
metrium
Men
ses
Men
ses
Men
ses
Men
ses
5days
5days
5 days
5 days
Fo
llicu
lar
Ph
ase
Fo
llicu
lar
Ph
ase
9 days9 days
Lu
teal
Ph
ase
Lu
teal
Ph
ase
14 days14 days
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Variation in Menstrual Cycle Length
35-daycycle
Ovulation
14 days14 days
Menses Foll. Phase Luteal Phase Menses
28-daycycle Menses Luteal Phase MensesFoll. Phase
25-daycycle Menses Foll. Phase MensesLuteal Phase
14 days14 days
5 days5 days
5 days5 days
5 days5 days
6 days6 days
9 days9 days
16 days16 days 14 days14 days
BreastTenderness
BreastTenderness
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Menstural Cycle Length
• AGELength
15 - 19 year olds 35 days 30 year olds 30 days 35 year olds 28 days
Variation More in teenagers Less in women in peak reproductive years