Puberty Flashcards
define puberty (5)
- acquisition of reproductive competence
- a transitional period that occurs over time, not one specific event
- influenced by genetic and environmental factors
- requires secretions of GnRH at appropriate frequency and quantity to stimulate gonadotropin release
- maturity of hypothalamus`
describe the hypothalamus pre-puberty, and what needs to happen to it during puberty
very sensitive to negative feedback pre-puberty, needs to gain sensitivity to positive feedback during puberty
list the 3 criteria for puberty onset in females
- age at 1st estrus
- age at 1st ovulation
- age of “safe” pregnancy
describe the age at first estrus as a criteria for puberty onset in females
age when female becomes sexually receptive, is easy to determine due to behavior change but silent ovulation will occur first time due to lack of progesterone priming
describe age at first ovulation as a criteria for puberty onset in females
must be evaluated with palpation or ultrasound due to silent ovulation, is difficult to determine without behavior change
which is the most practical criteria evaluation of puberty onset in females? why?
age of safe pregnancy, because even if first estrus and ovulation have occurred, pregnancy might not be safe for the female, as in the case of humans
list the 4 criteria for puberty onset in males
- age when behavior is expressed
- age at first ejaculation
- age when sperm first appear in ejaculate
- threshold number of sperm
describe the behavior a male expresses as a criteria of onset of puberty
mounting and erection; easily determined
is age at first ejaculation easy to distinguish?
no
what must occur in order to detect age when sperm first appear in ejaculation?
ejaculate has to be collected, usually through a BSE
what is the most practical and valid criteria for determining onset of puberty in males?
threshold number of sperm
what 4 factors influence puberty?
- hormonal
- genetic
- environment
- nutritional
which 2 of the 4 puberty-influencing factors can be controlled through management practices?
- environment
2. nutritional
hromonally, what is puberty dependent upon?
the hypothalamus’ ability to secrete enough GnRH
does GnRH secretion from the hypothalamus for puberty happen all at once or gradually? what causes this?
gradually, due to reduction in inhibition of hypothalamus
what 3 things are required for ovulation to occur in a female from puberty?
- full neural activity
- preovulatory GnRH surge
- hypothalamus must be able to respong to positive feedback from estradiol
what brian centers develop in the hypothalamus as a result of puberty in males and females?
female: tonic and surge center
male: tonic center only
describe the prepubertal period in terms on GnRH pulses and their results
- minimal GnRH release
- FSH and LH low
- minimal to no folliculogenesis or spermatogenesis
describe the pubertal period in terms of GnRH pulses and their results
- increase in GnRH pulse frequency and amplitude
- increase in FSH and LH pulses
- folliculogenesis and spermatogenesis occur
what is measured as a marker for GnRH levels and why?
LH levels because GnRH levels are very hard to measure (need to enter brain and shit)
describe pre-pubertal LH/GnRH pulses in a cow
4 pulses every 24 hours
describe tonic LH/GnRH pulses in a cow
6 pulses every 24 hours
describe surge LH/GnRH pulses in a cow
1 pulse every hour
list the 2 potential regulators of GnRH pulses at puberty in females
- development of surge center
2. change in feedback sensitivity to estradiol
what is the main aspect of genetics as an influencing factor on puberty?
breed differences
which type of cattle reaches puberty soon?
dairy
how does selection for certain traits affect puberty in swine?
when selected for litter size, age at puberty is lower; when selected for meat age at puberty is later
is there much effect of selection or breed difference on age at puberty in sheep?
not really
in energy partitioning, where does energy go first to be used?
maintenance first!
what has to happen in terms of body composition for puberty to occur?
the animal needs to hit a certain threshold of body composition in order to go through puberty
in terms of environment and social conditions, what happens when lots of females are housed together?
the age at puberty will decrease
what happens if a bunch of female animals SEE a male?
age at puberty will decrease even further
what is the recommended age to breed heifers?
15 months
what is the recommended age to breed bulls with natural mating?
15 months
what is the recommended age to breed bulls using AI?
12 months
what is the recommended age to breed a filly?
2-3 years
what is the recommended age to breed a colt?
2 years, earlier with AI
what is the recommended age to breed boars and sows?
9 months
