Estrous cycle and anestrus Flashcards
Estrous cycles:
Time period between periods of estrus (sexually receptive to male), physiological events occurring between successive periods of estrus
Average estrous cycle length in cow (include range):
Average length: 21 days
Range: 17-24 days
Average estrous cycle length in ewe (include range):
Average length: 17 days
Range: 13-19 days
Average estrous cycle length in sow (include range):
Average length: 21 days
Range: 17-25 days
Average estrous cycle length in mare (include range):
Average length: 21 days
Range: 15-26 days
Reproductive cyclicity importance:
Provides the female with repeated opportunities to become pregnant.
Estrous cycles begin and end with:
estrus
Menstrual cycle:
Predictable reproductive events beginning and ending with menses
Estrus is commonly referred to as:
heat
Estrus is a ______.
Estrous is an _______.
Estrual is an ________.
noun
adjective
adjective used to identify a condition related to estrous
Different types of reproductive cyclicity:
Polyestrus, seasonally polyestrus, monoestrus
Estrus causes a dramatic increase in:
estradiol
Domestic canids have about ____ estrous cycles every two years. Estrus lasts _______.
three
several days
The four periods of the estrous cycle:
Estrus, metestrus, diestrus, proestrus
Estrus
Period of sexual receptivity and mating
Estrus length:
12-18 hours in cow
Dominant hormone in estrus and its function:
Estradiol
Behavior changes (receptive rather than disinterested), changes in reproductive tract
Metestrus
Period between ovulation and formation of a functional corpus luteum
Events of metestrus:
Ovulation occurs 27-30 hours after start of estrus or 12-18 hours after end of estrus. CH to CL formation. Progesterone rises. Metestrus bleeding
Metestrus bleeding:
Noticed 35-45 hours after estrus. Capillary breakage causes blood in mucus. Occurs in 90% of heifers and 45% of cows. If seen, you have missed the window for breeding.
Diestrus
Period for preparing the uterus for pregnancy
What is present during diestrus?
A functional corpus luteum
Diestrus ends with (when pregnancy does not occur):
Luteolysis
Proestrus:
Begins with CL destruction and terminates at beginning of estrus
Proestrus is a major:
endocrine transition
Proestrus events:
Progesterone declines. Recruitment and rapid follicle growth. Estradiol increases (prepares estrus, positive feedback)
Proestrus only happens if:
progesterone decreases
Estrous cycle order:
Estrus -> metestrus -> diestrus -> proestrus -> estrus
What happens because of the GnRH-LH surge:
Ovulation, CL formation
Tonic LH secretion function:
CL function, follicle growth and turnover
When estradiol decreases, inhibin _______, resulting in an ______.
decreases, FSH surge
FSH surge results in _______ inhibin, _______ inhibin, resulting in ________.
increases, decreased, decreased, secondary surge
The bitch is receptive to the male during:
declining estrogen and rising progesterone
Anestrus length in bitch:
5 months
Proestrus length in bitch:
9 days
Estrus length in bitch:
9 days
Diestrus length in bitch:
2 months (pregnancy does not alter length)
In the bitch, ovulation occurs:
2-3 days after LH surge
In the bitch, fertilization is delayed _______ after ovulation because:
48-72 hours, ovum is not ready
Estrous cycle in the queen:
Proestrus -> estrus -> postestrus -> diestrus -> anestrus
In the queen, unless induced:
ovulation will not occur, so hormonal changes will not occur, P4 levels remain low.
In the queen, estrus lasts __ days and occurs every __ days.
9, 17
In the queen, during lactation:
cycling continues
What occurs after parturition in the queen?
Lactation and anestrus
Induced ovulators:
Alpaca, llama, queen
Anestrus
When cyclicity stops
Normal reasons for anestrus:
Pregnancy, parturition, uterine involution, lactation, offspring presence, season of the year.
Abnormal reasons for anestrus:
Stress, pathological conditions
Another name for pregnancy:
Gestational anestrus
Progesterone during pregnancy:
Negative feedback
After pregnancy, anestrus:
continues
Another name for lactation:
induced anestrus
Induced anestrus purpose:
Prevents new pregnancy before weaning young
