Puberty Flashcards
(43 cards)
Puberty definition
The ability to accomplish reproduction successfully
The physiological requirement is the development of specific hypothalamic neurons to release adequate quantities of GnRH
GnRH stimulates the release of gonadotropic hormones to promote…
Gametogenesis
Steroidogenesis
Development of reproductive tissues
Puberty in the female occurs at…
Attaining reproducing ability – first potentially fertile estrus followed by a luteal phase of normal length.
Different interpretations:
Age at 1st estrus
Age at 1st ovulation
Successful pregnancy
Puberty in the male occurs at…
Attaining reproducing ability – many ways to define
Age at behaving like a male
Age at 1st ejaculation
Age when sperm 1st appear in ejaculate
Age when sperm 1st appear in urine
Age when ejaculate has a threshold number of spermatozoa
Age of puberty in the bovine
Male- ~11m
Female- ~11m
Age of puberty in ovine/caprine
Male- ~7m
Female- ~7m
Age of puberty in porcine
Male- ~7m
Female- ~6m
Age of puberty in equine
Male- ~14m
Female- ~18m
Age of puberty in the canine
Male- ~9m
Female- ~12m
Large range due to breed
Age of puberty in the feline
Male- ~9m
Female- ~8m
Large range in female due to seasonal effects
Before puberty in male and females GnRH is released at…
Low amplitude and low frequency pulses of GnRH
After puberty in females and males the tonic center controls…
Basal levels of GnRH
But higher concentrations than before puberty
After puberty in the female the surge center controls…
Preovulatory surges of GnRH
The surge center is absent in…
Males
_________ is needed in males to defeminize the surge center in the male
Estradiol
In males testosterone crosses blood brain barrier, converted to estradiol in the brain
In males ________ crosses blood brain barrier, converted to estradiol in the brain to defeminize the surge center
testosterone
LH release in males
LH does not surge in the male
Consistent episodic release every 2-6 h and similar pattern of release of testosterone
Females have an estradiol surge about every 20 days resulting in…
Preovulatory LH surges
Centers of the hypothalamus in male vs female
Females = tonic and surge centers
Male = tonic center ONLY
Factors that effect the age of puberty
Body weight – major factor
40 – 50 % of mature weight – dictated by breed weight
usually when yearlings
Nutrition – Good nutrition – Moderate to high energy diets and 11-12% Crude Protein
animals on different planes of nutrition will reach puberty at different ages
Socio-environment – biostimulation – presence of male
Genetics – Sire scrotal circumference (SC) (larger -> earlier puberty)
Breed – purebred vs crosses
Birth season – fall born vs spring born
Density of housing groups (swine)
In cattle, a bull with a larger scrotal circumference will likely have daughters that…
Go into puberty earlier
Season effects on puberty
Month of birth influence age at puberty
SEASONAL BREEDERS!!
Sheep – short day breeders
-Born in Spring => puberty in Fall
-Born in Fall => puberty NEXT Fall
See this effect in BOTH males + females
Heifers can be influenced by season – those born in Fall reach puberty EARLIER than those born in Spring
Not the same for bull calves
Queens also affected by season
Inc. photoperiods in Jan./Feb. prompts onset of puberty
In sheep, if born in the spring they will go into puberty in the…
Fall
In a sheep is born in the fall then it will go into puberty….
NEXT fall (seen in males and females)
