Puberty Flashcards
Puberty
Ability to accomplish reproduction successfully. “Process” of acquiring reproductive competence.
Criteria/definitions for puberty in the female
Age at first ovulation (silent ovulation), age at first estrus, or age at which the female can support pregnancy without deleterious effects.
Which of the criteria/definitions for puberty in the female is most applicable practically?
Age at which the female can support pregnancy without deleterious effects
criteria/definitions for 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 appear in the urine
Age when the ejaculate contains a threshold number of sperm
What is the most valid criterion/definition for puberty in the male?
Age when the ejaculate contains a threshold number of sperm.
Average age of puberty in the female bovine:
11 months
Range of puberty age in the female bovine:
9-24 months
Average age of puberty in the male bovine:
11 months
Age range of puberty in the male bovine:
7-18 months
Average age of human male puberty:
13 years
Average age of human female puberty:
12 years
Is puberty sexual maturity?
No. Just because it can happen does not mean it should.
What is the fundamental requirement for the onset of puberty?
Secretion of GnRH at appropriate frequency and quantities to stimulate gonadotropin release form the AP
What does the secretion of GnRH at appropriate frequency and quantity, causing release of gonadotropins from the AP result in?
Promotion of gametogenesis, steroidogenesis, and development of reproductive tissues.
What are hormone levels like prior to puberty?
Low frequency and amplitude of GnRH, low LH and FSH in both males and females
LH pulse frequency and amplitude in the months leading up to puberty in heifers:
Increases months before puberty. It takes about 2 months before the pulse frequency is high enough to achieve puberty. Eventually get GnRH/LH surge
Onset of puberty in males and females:
Decreased hypothalamic sensitivity to negative feedback to testosterone/estrogen.
Puberty is associated with:
changes in feedback sensitivity of hypothalamus to estradiol.
The first LH surges after puberty are:
not always associated with estrus
What sensitizes the hypothalamus to estradiol to get behavioral estrus?
Progesterone
What happens after the first LH surge?
“Silent” ovulation
When does the first estrus begin, “silent” ovulation or first real ovulation?
First real ovulation
When does sensitization to hypothalamus estradiol occur?
When progesterone increases after “silent” ovulation
Changing features in peripuberal bulls:
Body conformation, increased aggressiveness and sexual desire, rapid growth of the penis and testicles, and separation of the penis from prepuce so extension is possible.
Testes size =
sperm production
Factors affecting age at puberty:
Genetics, metabolic/nutritional status, environment (seasonal breeders), and social cues (group housing)
Example of genetics influencing age at puberty:
Breed
Holstein female age (months): 8.5, male age: 9
Brahman female age (months): 19, male age: 17
Threshold of body size before puberty can be achieved means:
certain degree of “fatness” required for females
How does availability of energy change with growth?
In growing animals: food goes to growth, very little body fate, no excess energy
In animals close to maturity: excess energy, glucose, fatty acids, fat deposition
In seasonal breeders, _____________ influences age of puberty.
month of birth
Age of puberty in spring born ewe lambs:
6 months
Age of puberty in fall born ewe lambs:
12 months
Group housing in males (effects on puberty onset):
Large groups: normal onset
Smaller groups: delayed onset
Male exposure effect on puberty onset:
accelerated
Detrimental factors affecting puberty age:
Any factor that slows growth rate and reduces mature size of animal
Ex) nutritional stress, heat stress, poor sanitation, poor health
Minimizing age at puberty for males is _____ advantageous for females.
more
How is minimizing age at puberty in males more advantageous?
Reduces reproductive “down time” and reduces generation interval
Physiological demands of pregnancy/parturition/lactation limit:
benefits of hastening puberty in females
