Estrous Cycle

Question 1

When do estrous cycles begin in female farm animals?

Answer 1

After puberty

Question 2

What characterizes the estrous cycle in females?

Answer 2

Recurrent periods of receptivity to males, providing repeated opportunities to become pregnant.

Question 3

What marks the beginning and end of each estrous cycle?

Answer 3

Each cycle begins with estrus (heat) and ends at the subsequent estrus.

Question 4

What is the collective term for the hypothalamus, pituitary gland, and ovary in relation to the estrous cycle?

Answer 4

The hypothalamic-pituitary-ovarian axis

Question 5

What does “polyestrous” mean?

Answer 5

A type of reproductive cycle where females have multiple estrous cycles throughout the year.

Question 6

What characterizes “seasonally polyestrous” animals?

Answer 6

They have multiple estrous cycles during specific seasons of the year.

Question 7

What is meant by “monoestrous”?

Answer 7

A reproductive cycle where females have only one estrous cycle per year.

Question 8

What species are polyestrus?

Answer 8

cow, pig, queen, rodents

Question 9

What species are seasonal polyestrus SHORT DAY?

Answer 9

ewe, doe, elk, nanny

= fall breeding season

Question 10

What species are seasonal polyestrus LONG DAY?

Answer 10

mare = spring breeding season

Question 11

What species are monoestrus?

Answer 11

dog, wolf, fox, bear

Question 12

What is anestrus?

Answer 12

Period of reproductive quiescence. This long anestrus eriod is responsible for a cyclic profile of three cycles in two years

Question 13

What is proestrus?

Answer 13

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

Question 14

What is estrus?

Answer 14

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

Question 15

What is diestrus?

Answer 15

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

Question 16

What makes up the follicular phase

Answer 16

Proestrus and estrus

Question 17

What makes up the luteal phase

Answer 17

Diestrus and metestrus

Question 18

How long is the anestrus period?

Answer 18

5 months

Question 19

How long is the proestrus and estrus period?

Answer 19

9 days each

Question 20

How long is the diestrus period?

Answer 20

2 months

Question 21

What is the dominant ovarian structure and hormone in the follilcular phase

Answer 21

Structure = large antral follciles

Hormone = estrogen produced by preovulatory follicles

Question 22

What is the dominant ovarian structure and hormone in the luteal phase

Answer 22

Structure = corpora lutea

Hormone = progesterone

Question 23

What phase does ovulation occur in?

Answer 23

Estrus phase of the estrous cycle

Question 24

What occurs during proestrus?

Answer 24

Maturation of ovulatory follicles and secretion of estrogen.

Question 25

What characterizes the estrus stage?

Answer 25

Sexual receptivity and peak secretion of estrogen.

Question 26

What happens during metestrus?

Answer 26

Formation of the corpus luteum and beginning of progesterone secretion.

Question 27

What is the main hormone involved in diestrus?

Answer 27

Sustained luteal secretion of progesterone.

Question 28

What can you look at to determine stage of estrous cycle in a normally cycling animal? (4)

Answer 28

1. Behavioural changes 2. Visible physical signs 3. Palpation/visualization of the reproductive organs 4. Blood/fluid hormone levels

Question 29

What can you look for during sexual behaviour at heat? (3)

Answer 29

* standing for mounting by a male of the same species (“standing heat”; heterosexual) * standing for mounting by another female * attempting to mount another female

Question 30

What are some associated behaviour changes? (5)

Answer 30

* 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

Question 31

What are some visible physical signs to look for when determining phase of cyclicity? (3)

Answer 31

-Cervical mucous discharge from the vulva -Swelling of the vulva -Reddening of vaginal mucosa

Question 32

What features of the ovaries do you look at when palpating?

Answer 32

* 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

Question 33

What features of the uterus do you look at when palpating?

Answer 33

* Turgidity or flaccidity of uterus and cervix reflect the ovarian state and provide useful information.

Question 34

What happens to the mares cervix and uterus during estrus?

Answer 34

its flaccid at this point

Question 35

What happens to the cows cervix and uterus during estrus?

Answer 35

Cow has increased cervical and uterine tone during estrus and is more flaccid at other times.

Question 36

What are the four hormones to look for in blood/fluid and when they are useful

Answer 36

->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.

Question 37

LH has a single defined peak when

Answer 37

a few hours before ovulation

Question 38

Τ/F FSH and LH are used as indicators of estrus stage very commonly

Answer 38

F

Question 39

T/F FSH has various peaks during ovulation that vary by species

Answer 39

T

Question 40

What are the 3 PHASES of the follicular wave

Answer 40

growing phase; static phase; regressing phase

Question 41

What are the 4 STAGES of the follicular wave

Answer 41

recruitment, selection, dominance, atresia

Question 42

recruitment: _____ FSH, ____ LH, ___ inhibin, _____ estradio

Answer 42

high; low; no; no

Question 43

selection: ___ FSH, ____ LH, ____ inhibin

Answer 43

low; moderate; low

Question 44

dominance: ___ FSH, ____ LH, ____ inhibin

Answer 44

low; high; high

Question 45

What characterizes atresia?

Answer 45

Degeneration of follicles

Question 46

How does the menstral cycle differ from estrus cycles (3)

Answer 46

* No defined period of sexual receptivity * Period of menses * Cycle begins or ends with menses

Question 47

how do reflex ovulators differ from spontaneous ovulators

Answer 47

reflex: require stimulation of cervix or vagina for ovulation; usually longer period of copulation or more frequent copulation

Question 48

the most GnRH release occurs during what stage of ovulation (follicular or luteal)

Answer 48

follicular