Puberty

Question 1

define puberty (5)

Answer 1

1. acquisition of reproductive competence
2. a transitional period that occurs over time, not one specific event
3. influenced by genetic and environmental factors
4. requires secretions of GnRH at appropriate frequency and quantity to stimulate gonadotropin release
5. maturity of hypothalamus`

Question 2

describe the hypothalamus pre-puberty, and what needs to happen to it during puberty

Answer 2

very sensitive to negative feedback pre-puberty, needs to gain sensitivity to positive feedback during puberty

Question 3

list the 3 criteria for puberty onset in females

Answer 3

1. age at 1st estrus
2. age at 1st ovulation
3. age of “safe” pregnancy

Question 4

describe the age at first estrus as a criteria for puberty onset in females

Answer 4

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

Question 5

describe age at first ovulation as a criteria for puberty onset in females

Answer 5

must be evaluated with palpation or ultrasound due to silent ovulation, is difficult to determine without behavior change

Question 6

which is the most practical criteria evaluation of puberty onset in females? why?

Answer 6

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

Question 7

list the 4 criteria for puberty onset in males

Answer 7

1. age when behavior is expressed
2. age at first ejaculation
3. age when sperm first appear in ejaculate
4. threshold number of sperm

Question 8

describe the behavior a male expresses as a criteria of onset of puberty

Answer 8

mounting and erection; easily determined

Question 9

is age at first ejaculation easy to distinguish?

Answer 9

no

Question 10

what must occur in order to detect age when sperm first appear in ejaculation?

Answer 10

ejaculate has to be collected, usually through a BSE

Question 11

what is the most practical and valid criteria for determining onset of puberty in males?

Answer 11

threshold number of sperm

Question 12

what 4 factors influence puberty?

Answer 12

1. hormonal
2. genetic
3. environment
4. nutritional

Question 13

which 2 of the 4 puberty-influencing factors can be controlled through management practices?

Answer 13

1. environment

2. nutritional

Question 14

hromonally, what is puberty dependent upon?

Answer 14

the hypothalamus’ ability to secrete enough GnRH

Question 15

does GnRH secretion from the hypothalamus for puberty happen all at once or gradually? what causes this?

Answer 15

gradually, due to reduction in inhibition of hypothalamus

Question 16

what 3 things are required for ovulation to occur in a female from puberty?

Answer 16

1. full neural activity
2. preovulatory GnRH surge
3. hypothalamus must be able to respong to positive feedback from estradiol

Question 17

what brian centers develop in the hypothalamus as a result of puberty in males and females?

Answer 17

female: tonic and surge center
male: tonic center only

Question 18

describe the prepubertal period in terms on GnRH pulses and their results

Answer 18

1. minimal GnRH release
2. FSH and LH low
3. minimal to no folliculogenesis or spermatogenesis

Question 19

describe the pubertal period in terms of GnRH pulses and their results

Answer 19

1. increase in GnRH pulse frequency and amplitude
2. increase in FSH and LH pulses
3. folliculogenesis and spermatogenesis occur

Question 20

what is measured as a marker for GnRH levels and why?

Answer 20

LH levels because GnRH levels are very hard to measure (need to enter brain and shit)

Question 21

describe pre-pubertal LH/GnRH pulses in a cow

Answer 21

4 pulses every 24 hours

Question 22

describe tonic LH/GnRH pulses in a cow

Answer 22

6 pulses every 24 hours

Question 23

describe surge LH/GnRH pulses in a cow

Answer 23

1 pulse every hour

Question 24

list the 2 potential regulators of GnRH pulses at puberty in females

Answer 24

1. development of surge center

2. change in feedback sensitivity to estradiol

Question 25

what is the main aspect of genetics as an influencing factor on puberty?

Answer 25

breed differences

Question 26

which type of cattle reaches puberty soon?

Answer 26

dairy

Question 27

how does selection for certain traits affect puberty in swine?

Answer 27

when selected for litter size, age at puberty is lower; when selected for meat age at puberty is later

Question 28

is there much effect of selection or breed difference on age at puberty in sheep?

Answer 28

not really

Question 29

in energy partitioning, where does energy go first to be used?

Answer 29

maintenance first!

Question 30

what has to happen in terms of body composition for puberty to occur?

Answer 30

the animal needs to hit a certain threshold of body composition in order to go through puberty

Question 31

in terms of environment and social conditions, what happens when lots of females are housed together?

Answer 31

the age at puberty will decrease

Question 32

what happens if a bunch of female animals SEE a male?

Answer 32

age at puberty will decrease even further

Question 33

what is the recommended age to breed heifers?

Answer 33

15 months

Question 34

what is the recommended age to breed bulls with natural mating?

Answer 34

15 months

Question 35

what is the recommended age to breed bulls using AI?

Answer 35

12 months

Question 36

what is the recommended age to breed a filly?

Answer 36

2-3 years

Question 37

what is the recommended age to breed a colt?

Answer 37

2 years, earlier with AI

Question 38

what is the recommended age to breed boars and sows?

Answer 38

9 months