Estrous Cycle Flashcards
When do estrous cycles begin in female farm animals?
After puberty
What characterizes the estrous cycle in females?
Recurrent periods of receptivity to males, providing repeated opportunities to become pregnant.
What marks the beginning and end of each estrous cycle?
Each cycle begins with estrus (heat) and ends at the subsequent estrus.
What is the collective term for the hypothalamus, pituitary gland, and ovary in relation to the estrous cycle?
The hypothalamic-pituitary-ovarian axis
What does “polyestrous” mean?
A type of reproductive cycle where females have multiple estrous cycles throughout the year.
What characterizes “seasonally polyestrous” animals?
They have multiple estrous cycles during specific seasons of the year.
What is meant by “monoestrous”?
A reproductive cycle where females have only one estrous cycle per year.
What species are polyestrus?
cow, pig, queen, rodents
What species are seasonal polyestrus SHORT DAY?
ewe, doe, elk, nanny
= fall breeding season
What species are seasonal polyestrus LONG DAY?
mare = spring breeding season
What species are monoestrus?
dog, wolf, fox, bear
What is anestrus?
Period of reproductive quiescence. This long anestrus eriod is responsible for a cyclic profile of three cycles in two years
What is proestrus?
Proestrus begins with the appearance of a blood-tinged vaginal discharge and by vaginal swelling. It ends when the bitch accepts the male for mating. The ovaries contain large follicles at the onset of proestrus. Estradiol gradually increases and peaks slightly before the onset of estrus
What is estrus?
Shortly after peak estradiol, behavioural estrus beings. Both LH and FSH peak in early estrus. Ovulation is completed at about the third day of estrus and fertilization is completed at about the 6th day. P4 increases during the latter part of estrus signifying luteinization
What is diestrus?
Both pregnany and open bitches are considered to be in diestrus. Pregnancy status doesnt alter length of diestrus. P4 peaks at about 15 days then decreases gradually. Bitches that dont get pregnant are often considered to be pseudopregnant
What makes up the follicular phase
Proestrus and estrus
What makes up the luteal phase
Diestrus and metestrus
How long is the anestrus period?
5 months
How long is the proestrus and estrus period?
9 days each
How long is the diestrus period?
2 months
What is the dominant ovarian structure and hormone in the follilcular phase
Structure = large antral follciles
Hormone = estrogen produced by preovulatory follicles
What is the dominant ovarian structure and hormone in the luteal phase
Structure = corpora lutea
Hormone = progesterone
What phase does ovulation occur in?
Estrus phase of the estrous cycle
What occurs during proestrus?
Maturation of ovulatory follicles and secretion of estrogen.
What characterizes the estrus stage?
Sexual receptivity and peak secretion of estrogen.
What happens during metestrus?
Formation of the corpus luteum and beginning of progesterone secretion.
What is the main hormone involved in diestrus?
Sustained luteal secretion of progesterone.
What can you look at to determine stage of estrous cycle in a normally cycling animal? (4)
- Behavioural changes
- Visible physical signs
- Palpation/visualization of the reproductive organs
- Blood/fluid hormone levels
What can you look for during sexual behaviour at heat? (3)
- standing for mounting by a male of the same species (“standing heat”;
heterosexual) - standing for mounting by another female
- attempting to mount another female
What are some associated behaviour changes? (5)
- restlessness
- licking or sniffing other animals
- chin pressing on rump or back of another animal
- increased vocalization and urination
- “winking“-mares that are in estrus usually stand calmly, squat and move the labia of the vulva (“wink”) in the presence of a stallion
What are some visible physical signs to look for when determining phase of cyclicity? (3)
-Cervical mucous discharge from the vulva
-Swelling of the vulva
-Reddening of vaginal mucosa
What features of the ovaries do you look at when palpating?
- Number & size of antral follicles
- Presence of the corpus luteum
- Additional advantage of visualization/palpation: abnormal structures (cysts, tumors, unexpected/pathological pregnancy) may explain abnormalities in the observed behavioral traits, cytologic characteristics and hormonal profiles
What features of the uterus do you look at when palpating?
- Turgidity or flaccidity of uterus and cervix reflect the ovarian state and provide useful information.
What happens to the mares cervix and uterus during estrus?
its flaccid at this point
What happens to the cows cervix and uterus during estrus?
Cow has increased cervical and uterine tone during estrus
and is more flaccid at other times.
What are the four hormones to look for in blood/fluid and when they are useful
->Estrogen - main hormone of estrus (produced by granulosa cells). High in estrus, rising in proestrus, low in diestrus
->Progesterone - primary hormone of diestrus and pregnancy (produced by cells of the corpus luteum and gravid uterus). Low in
estrus, rising in metestrus, high in diestrus and pregnancy.
->Follicle Stimulating Hormone (FSH) - Not often used as an indicator of stage of estrus but has various peaks in cycle which vary widely according to species.
->Luteinizing Hormone (LH) - Not often used as an indicator of estrus stage, but has a single defined peak of expression several hours before ovulation.
LH has a single defined peak when
a few hours before ovulation
Τ/F FSH and LH are used as indicators of estrus stage very commonly
F
T/F FSH has various peaks during ovulation that vary by species
T
What are the 3 PHASES of the follicular wave
growing phase; static phase; regressing phase
What are the 4 STAGES of the follicular wave
recruitment, selection, dominance, atresia
recruitment: _____ FSH, ____ LH, ___ inhibin, _____ estradio
high; low; no; no
selection: ___ FSH, ____ LH, ____ inhibin
low; moderate; low
dominance: ___ FSH, ____ LH, ____ inhibin
low; high; high
What characterizes atresia?
Degeneration of follicles
How does the menstral cycle differ from estrus cycles (3)
- No defined period of
sexual receptivity - Period of menses
- Cycle begins or ends with menses
how do reflex ovulators differ from spontaneous ovulators
reflex: require stimulation of cervix or vagina for ovulation; usually longer period of copulation or more frequent copulation
the most GnRH release occurs during what stage of ovulation (follicular or luteal)
follicular
