AGR 506 Reproductive Cyclicity

What is the purpose of the Estrus cycle?

Provides females with repeated opportunities to become pregnant

What are the 3 types of estrous cyclicity?

-Polyestrus

-Seasonally Polyestrus,

-Monoestrus

What is Monoestrus?

Only one cycle per year

Periods of estrus that last for several days

(Increases probability that mating and pregnancy can occur)

What species are Monoestrous?

Dogs

Wolves

Foxes

Bears

What is Polyestrus?

Uniform distribution of estrus cycles throughout the entire year

Can become pregnant throughout the entire year

What species are Polyestrus?

Cattle

Cat

Swine

Rodents

What is Seasonal Polyestrus?

Display clusters of estrous cycles that occur only during a certain season of the year

Long and Short Day Breeders

What species are Seasonally polyestrus?

Horses

Sheep

Goats

Deer

Elk

What species are long day breeders?

Horses

What species are short day breeders?

sheep and goats

What happens for short day breeders hormonely?

-Increase in melatonin

-Inhibition of Kisspeptin

-Elevates GnRH

-Elevates FSH and LH to initiate cyclicity

Domestic canids typically have _____ estrous cycles every ____ years

3 cycles; 2 years

What is the HORSES length of estrus cycle? (mean)

21 days

What is the HORSES duration of estrus? (mean)

7 days

What is a HORSES time from onset of estrus and LH surge to ovulation?

5 days of estrus to ovulation

2 days from LH surge to ovulation

What is the COWS length of estrus cycle? (mean)

21 days

What is the COWS duration of estrus? (mean)

15 hours

What is a COWS time from onset of estrus and LH surge to ovulation?

24-32 hours of estrus to ovulation

28 hours from LH surge to ovulation

What is the PIGS length of estrus cycle? (mean)

21 days

What is the PIGS duration of estrus? (mean)

50 hours

What is a PIGS time from onset of estrus and LH surge to ovulation?

36-44 hours of estrus to ovulation

40 hours from LH surge to ovulation

What is the CATS length of estrus cycle? (mean)

17 days

What is the CATS duration of estrus? (mean)

9 days

What is a CATS time from onset of estrus and LH surge to ovulation?

Induced Ovulator

40 hours from LH surge to ovulation

What is the DOGS length of estrus cycle? (mean)

6 months

What is the DOGS duration of estrus? (mean)

9 days

What is a DOGS time from onset of estrus and LH surge to ovulation?

4-24 days of estrus to ovulation

2-3 days from LH surge to ovulation

What are the two major phases of the estrous cycle?

-Follicular

-Luteal

What is the follicular phase?

Period from regression of CL to ovulation

What percentage of estrus does the follicular phase usually last?

20%

What is the primary ovarian structure in the follicular phase?

Antral follicles

What is the primary hormone in the follicular phase?

Estradiol

What is the luteal phase?

The period from ovulation until CL regression

What percentage of estrus does the luteal phase usually last?

80%

What is the primary ovarian structure in the luteal phase?

CL

What is the primary hormone in the luteal phase?

Progesterone

What are the 4 stages of estrous?

-Proestrus

-Estrus (Heat)

-Metestrus

-Diestrus

Which two estrus stages occur during the follicular phase?

-Proestrus

-Estrus

Which two estrus stages occur during the luteal phase?

-Metestrus

-Diestrus

What is Proestrus?

A estrus stage that begins when progesterone declines as an result of luteolysis (destruction of CL)

What does Proestrus do and how does the antral follicles change?

Terminates at the onset of estrus

Antral follicles mature for ovulation and female reproductive system prepares for onset estrus and mating

How long does Proestrus last?

2-5 days depending on species

What is Estrus?

The period when female allows copulation

Most recognizable stage

What is the dominant hormone in estrus?

Estradiol

Estrus is a gradual process what may increase during this time?

-Locomotion

-Phonation

-Nervousness

-Attempts at mating other animals

What is standing estrus?

Willing to accept male for mating

What is Lordosis?

Back arching in preparation for mating

How long does Estrus last?

Depends on the species

What is Metestrus?

The transition from estradiol dominance to progesterone dominance

Period between ovulation and formation of functional CL

What happens to the newly ovulated follicle during metestrus?

Undergoes cellular and structural remodeling

What is luteinization?

Formation of intraovarian endocrine gland (CL)

How many days are required after ovulation before the newly formed CL produces significant quantities of progesterone?

2-5 days

What is Diestrus?

The period of maximum luteal function when the CL is fully functional and progesterone secretion is high

When does Diestrus end?

When the CL is destroyed (luteolysis)

How long does Diestrus usually last?

10-14 days (duration is directly related to length of time that CL remains functional)

What happens during Proestrus staging?

Formation of ovulatory follicles and estradiol secretion

What happens during Estrus staging?

Sexual receptivity and peak estradiol secretion

What happens during Metestrus staging?

CL formation and beginning of progesterone secretion

What happens during Diestrus staging?

Sustained luteal secretion of progesterone

What makes the dogs stage sequence in their estrous cycle different?

No defined metestrus

How long does a dogs anestrus usually last?

20 weeks

What is Superfecundation?

Multiple ovulations produce multiple oocytes during a single estrus period

Which can be fertilized by different males

What makes the cats stage sequence in their estrous cycle different?

No metestrus

Goes back into proestrus after estrus

What makes a cat's ovulation different from other species?

They are induced ovulators and copulation is required for induction of LH surge

What happens when a cat doesn't copulate?

Neither. metestrus nor diestrus occurs

Remains in constant follicular phase until copulation

What is Anestrus?

Condition when a female doesn't exhibit estrous cycles

What are the types of Anestrus?

-Seasonal

-Gestational

-True

-Apparent

Examples of True vs Apparent Anestrus

True: Insufficient hormonal stimuli

Apparent: Failure to detect estrus or failure to detect that female is pregnant

What is Gestational Anestrus?

Normal condition brought about by inhibition of GnRH release by progesterone from pregnancy

What is Seasonal anestrus?

As days shorten, cycling stops

What is the period when cyclicity stops?

-Polyestrus

-Proestrus

-Estrus

-Anestrus

Anestrus

Which type of estrous cyclicity does the mare display?

-Seasonally polyestrous - short day

-Monoestrous

-Seasonally polyestrous - long day

-Polyestrous

Seasonally polyestrous - Long day

Which of the following is true regarding the luteal phase of the estrous cycle?

-Dominant ovarian structures are antral follicle; Primary reproductive hormone is progesterone

-Dominant ovarian structures are CL; Primary reproductive hormone is progesterone

-Dominant ovarian structures are CL; Primary reproductive hormone is estradiol

-Dominant ovarian structures are antral follicle; Primary reproductive hormone is estradiol

Dominant ovarian structures are CL; Primary reproductive hormone is progesterone

Which of the following estrous stages is the period when a female allows copulation?

-Proestrus

-Estrus

-Diestrus

-Metestrus

Estrus

Ture or False: Queens are induced ovulators and copulation is required for induction of LH surge

True