ansc 320 - EXAM II fall 2026

Puberty originates from the latin word?

Pubscere

Old World definition of Puberty

ability to accomplish reproduction successfully

New World definition of Puberty

“process” of acquiring reproductive competence

Criteria for Puberty in the Female

• Age at first ovulation “Silent Ovulation”

• Age at first estrus

What is widely known as the main indicator of Puberty in the female?

Age at first estrus

What is another criteria for identifying Puberty in the Female?

Age at which the female can support pregnancy without deleterious effects

Criteria for Puberty in the Male

• Age when behavioral traits are expressed

• Age at first ejaculation

• Age when sperm first appear in ejaculate & urine

What is the most valid criterion for identifying Puberty in the Male?

Agen when the ejaculate contains a threshold number of sperm

Features that change in Peri puberal Bulls

• body conformation

• Increased aggressiveness & sexual desire

• Rapid growth of penis & testicles

• Separation of the penis from prepuce (so extension is possible)

Testes size = ?

sperm production

Age of Puberty in Bovine: Males

11 months

Age of Puberty in Bovine: Females

11 months

Age of Puberty in Human: Males

13 years old

Age of Puberty in Human: Females

12 years old

Puberty is NOT?

sexual maturity

What is the fundamental requirement for Onset of Puberty?

secretion of GnRH at appropriate frequency and quantities to stimulate gonadotropin release from AP

What is another Fundamental Requirement for Onset of Puberty?

promotion of gametogenesis, steroidogenesis & development of reproductive tissues

Before puberty, what are the levels of GnrH in the male and female?

low frequency & amplitude; low LH & FSH

How long does it take for an LH pulse to reach a high frequency, which induces Puberty?

about 2 months

How often is an LH/GnRH surge in the cow?

every 21 days

Decreased Hypothalamic Sensitivity leads to what kind of feedback system in Testosterone/Estrogen?

negative feedback loop

Puberty is associated with?

changes in Feedback sensitivity of Hypothalamus to Estradiol

Factors Affecting Age at Puberty

• Genetics

• Metabolic/Nutritional Status

• Environment (seasonal breeders)

• Social cues (Group housing)

Average age at Puberty: Holstein Males

8.5 months

Average age at Puberty: Holstein Females

9 months

Average age at Puberty: Brahman Males

19 months

Average age at Puberty: Brahman Females

17 months

A certain degree of what is required for Females to achieve Puberty?

body fat

Availability of energy changes with?

Growth

Growing Animals

• food goes to growth

• Very little body fat

• No excess energy

Animals close to Maturity

• Excess energy

• Glucose, Fatty Acids, Fat deposition

Detrimental Factors Affecting Puberty Age

any factor that slows growth rate and reduces mature size of animal

Examples of detrimental factors affecting puberty age

• Nutritional stress

• Heat stress

• Poor sanitation

• Poor health

Minimizing age at puberty in WHO is more advantageous than females?

Males

Minimizing age at puberty in Males reduces what?

• reproductive “down time”

• generation interval

Physiological demands of pregnancy/parturition/lactation limit what?

the hastening of puberty in females

Estrous Cycles

time period between periods of estrus (sexually receptive to male)

Estrus

physiological events occurring between successive periods of sexual receptivity

Sequence of Reproductive Events

Puberty —> Copulation —> Estrous cycle —> Anestrus

Average length of Estrous cycle in Cows?

21 days

Avg. length of Estrous in Ewes?

17 days

Avg. length of Estrous in Sows?

21 days

Avg. length of Estrous in the Mare?

21 days

Estrous can range between what days?

15-26 days

Reproductive cyclicity provides the Female with what?

repeated opportunities to become pregnant

What are the two types of cycles a mammal can experience?

Estrous & Menstrual Cycle

Estrous cycles

predictable reproductive events between periods of estrus

Menstrual cycle

predictable reproductive events beginning and ending with menses

Estrus is commonly referred to as?

Heat

What are the British and European terms for Estrous and Estrus?

Oestrus & Oestrous

What are the three types of Reproductive Cyclicity?

• Polyestrus

• Seasonally Polyestrus

• Monoestrus

What kind of animals are Polyestrus?

Cow, female cat, pig rodents

What species is Seasonally Polyestrus (Long Day)?

the Mare

What species are Seasonally Polyestrus (Short Day)?

Ewe, doe, elk, goat

What species are Monoestrus?

dog, wolf, fox, and bear

Domestic canids have how many estrous cycles every two years?

about 3

What are the 4 periods of the Estrus cycle?

1) Estrus

2) Metestrus

3) Diestrus

4) Proestrus

What is the first step in the Estrous cycle?

Proestrus

What is the 2nd step in the Estrous cycle?

Estrus

What is the 3rd step in the Estrous cycle?

Ovulation

What is the 4th step in the Estrous cycle?

Metestrus

What is the 5th step Estrous cycle?

Diestrus

Estrus

period of sexual receptivity and mating

Standing heat is called?

Lordosis

What is the dominant hormone during Estrus?

Estradiol

How long does Estrus last in a cow?

12-18 hours

Metestrus

period between ovulation and formation of a functional corpus luteum

How many hours after start of Estrus does Ovulation occur?

27-30 hours

How many hours after the end of Estrus does Ovulation occur?

12-18 hours

During Metestrus, the Corpus Hemorrhagium turns into?

a Corpus Luteum

Characteristics of Metestrus

• corpus hemorrhagicum —> corpus luteum

• progesterone RISES

• Metestrus bleeding (35-45 h after estrus)

• Capillary breakage (decreased estrogen)

What hormone RISES during Metestrus?

progesterone

How long after Estrus does Metestrus bleeding occur?

34-45 hours

Capillary breakage during Metestrus leads to a decrease in what hormone?

Estrogen

Diestrus

period for preparing uterus for pregnancy

What are the two main factors of Diestrus?

• a functional CL

• high progesterone

Proestrus

begins with Corpus Luteum destruction, and terminates at the beginning of estrus

Which phase of the Estrous Cycle has major endocrine transition?

Proestrus

What hormone is low during Proestrus?

progesterone

Characteristics of Proestrus

• Recruitment and rapid follicle growth

• Estradiol increases (prepare for estrus and mating)

The GnRH-LH surge is important for what?

• Ovulation

• Corpus Luteum formation

What effect does the GnRH-LH surge have on Ovulation?

Causes the dominant follicle to rupture and release a mature oocyte

What effect does the GnRH-LH surge have on Corpus Luteum formation?

high levels of Estrogen from the dominant follicle cause a positive feedback loop in the Hypothalamus to release GnRH. GnRH acts on the Ant. Pituitary, releasing Luteinizing Hormone as a result (LH).

Tonic LH Secretion is responsible for what?

• CL function

• Follicle Growth & Turnover

Estrogen induces what kind of surge?

LH surge

What is the function of an FSH surge?

• secondary

• Follicle recruitment

In the dog, Ovulation occurs how long after LH surge?

2-3 days

Cats are ____________ ovulators?

induced

Posterus is specific to what species?

cats

Postestrus

Lack of ovulation, corpus luteum; remain in follicular phase until Copulation

What is the mean duration of Estrus in the dog?

9 days

What is the mean duration of Estrus in the Cow?

15 hours

What is the mean duration of Estrus in the Sheep?

30 hours

What is the mean duration of Estrus in the Mare?

7 days

What is the mean duration of Estrus in the cat?

9 days

What is the mean duration of Estrus in the Sow?

50 hours

Anestrus

when cyclicity stops

Main reasons for Anestrus

• Parturition

• Uterine involution

• Lactation

• Offspring presence

• Season

Other reasons for Anestrus

• Pregnancy

• Stress (poor nutrition & other reasons)

• Uterine infection

• Persistent CL

• Mummified fetus