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Animal Science 434. Lecture 8: The Onset of Puberty. Development of Hypothalamus and GnRH Release Centers. Males and Females are Different!!!. Hypothalamus GnRH Control Centers in the Female. Why does the male only have tonic control centers develop?. Male Brain Development. T. Testis.

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animal science 434

Animal Science 434

Lecture 8: The Onset of Puberty

hypothalamus gnrh control centers in the female
Hypothalamus GnRH Control Centers in the Female

Why does the male

only have tonic control

centers develop?

male brain development
Male Brain Development

T

Testis

T

E2

Surge Center

Does not

Develop

Blood Brain

Barrier

female brain development
Female Brain Development

Placenta

E2

E2

E2

E2

Ovary

Blood Brain

Barrier

female brain development6
Female Brain Development

aFP + E2

Placenta

E2

E2

E2

E2

Ovary

Surge Center

Develops

Blood Brain

Barrier

slide7

Fundamental Male and Female Differences

PulsePatterns

Surge + Tonic

Tonic

puberty
Puberty

The ability to accomplish reproduction successfully.

puberty in the female
Puberty in the Female
  • Age at first estrus (heat)
  • Age at first ovulation
  • Age at which the female can support pregnancy
puberty in the male
Puberty in the Male
  • Age when behavioral traits are expressed
  • Age at first ejaculation
  • Age when sperm first appear in the ejaculate
  • Age when sperm first appear in the urine
  • Age when the ejaculate contains a threshold number of sperm
average age of puberty range
Average Age of Puberty (Range)

Species Male Female

Bovine 11 mo (7-18) 11 mo (9-24)

Ovine 7 mo (6-9) 7 mo (4-14)

Porcine 7 mo (5-8) 6 mo (5-7)

Equine 14 mo (10-24) 18 mo (12-19)

Human 13 yr 12 yr

Canine 9 mo (5 - 12) 12 mo (6 - 24)

Feline 9 mo (8 - 10) 8 mo (4 -12)

puberty12
Puberty

Genetic

Hormonal

Environment

Nutritional

gnrh pulses determine puberty
GnRH Pulses Determine Puberty
  • Prepubertal period
    • minimal GnRH release
    • FSH and LH low
    • minimal to no folliculargenesis or spermatogenesis
  • Puberty
    • increase in the pulse frequency and amplitude of GnRH release
    • increase in FSH and LH pulses
    • folliculargenesis and spermatogenesis occur
changes in gnrh secretion with puberty
Changes in GnRH Secretion With Puberty

Surge

Tonic

Low Amplitude and Frequency

slide19

Surge

Tonic

potential regulators of gnrh pulses at puberty
Potential Regulators of GnRH Pulses at Puberty
  • Development of surge center
  • Change in the feedback sensitivity to estradiol
development of the hypothalamic gnrh surge center22
Development of the Hypothalamic GnRH Surge Center

Puberty = 28 - 30 weeks

Positive Feedback is possible prior to puberty

puberty in the stallion
Puberty in the Stallion

Puberty

FSH

LH (ng/ml)

FSH (ng/ml)

Testosterone (ng/ml)

LH

T

slide28

Caused by

GnRH

Increased Gonadotropins

FSH

LH (ng/ml)

FSH (ng/ml)

Testosterone (ng/ml)

LH

T

slide29

Sertoli cells mature and multiply

  • Spermatogonia begin to divide

Testosterone Remains Low

FSH

LH (ng/ml)

FSH (ng/ml)

Testosterone (ng/ml)

LH

T

slide30

FSH Increases

Puberty

FSH

LH (ng/ml)

FSH (ng/ml)

Testosterone (ng/ml)

LH

T

Sperm found in the ejaculate

Testosterone Increases

influence of breed on age of puberty
Influence of Breed on Age of Puberty

Average Age at Puberty (Months)

effect of 2 deoxyglucose on lh pulses
Effect of 2-deoxyglucose on LH Pulses

GnRH

Before 2DG

During 2DG

3

2

LH (ng/ml)

1

0

1

2

3

4

5

6

7

8

9

10

11

Time (hours)

effect of 2 deoxyglucose on lh pulses36
Effect of 2-deoxyglucose on LH Pulses

GnRH

Before 2DG

During 2DG

3

2

LH (ng/ml)

1

0

1

2

3

4

5

6

7

8

9

10

11

Time (hours)

Decreased Amplitude and

Frequency

metabolic signals influence gnrh neurons
Metabolic Signals Influence GnRH Neurons

Blood Glucose

Glucose sensingneurons

?

Neuropeptide Y neurons

GnRH neurons

GnRH

Leptin

Fatty Acid sensing neurons

?

Adipocytes

(Fat)

Blood Fatty Acids

effect of nutrition on puberty
Effect of Nutrition on Puberty

12

1.5 lb/day

2.0 lb/day

10

8

1.2 lb/day

Body Weight (X 100 lbs.)

6

Puberty

4

2

0

4

8

12

0

16

20

24

Age (months)

mature weight at puberty
% Mature Weight at Puberty

Dairy Cattle 30-40%

Beef cattle 55-65%

Sheep 40- 63%

slide42

32

Weeks

28

Weeks

24 Weeks

24 Weeks

influence of growth rate and bull exposure on age of puberty
Influence of Growth Rate and Bull Exposure on Age of Puberty

Moderate Growth Rate

High Growth Rate

500

449

428

422

400

375

300

Age at Puberty (days)

200

100

0

Heifers

only

Bull

Exposure

puberty44
Puberty

Genetic

Hormonal

Environment

Nutritional

recommended age to breed
Recommended Age to Breed
  • Heifer 15 months (65% mature BW)
  • Bull 15 natural mating, 12 months AI
  • Filly 2-3 years
  • Colt 2 years
  • Boar 9 months