Puberty and Maturity Flashcards
Definition of ovulation
The phase of a female’s menstrual cycle in which a mature egg is released from the ovarian follicles into the oviduct
what happens during luteal phase?
Egg will be available to be fertilised by sperm.
Associated with the largest actively growing follicles present when the previous CL regressed (-progesterone, +FSH +LH)
Explains Induced ovulators
Animals: rabbit cat and camel
Induced by intromission (the insertion of one object into another, such as the introduction of the penis into the vagina)
Coitus induced ovulation
Spontaneous ovulators
Farm animals and humans
- controlled by events of estrus cycle and not affected by intromission
Reached puberty when
Female: Considered first estrus
Male: Appearance of enough sperm in ejaculate to impreganate female
Criteria for onset of puberty
Male
- Age to showing interest in female
- Age at first ejaculation
- Age when sperm first observed in ejaculate
- Age when sperm are observed in the urine
- Age when ejaculate is confirmed fertile
- Mounting and erection (occurs before ejaculation)
Criteria for onset of puberty (female)
- Age at first estrus
- Age at first ovulation
- Age at first conception
- Age at which females can support pregnancy
What happens during puberty?
Release of GnRH in high frequency and high amplitude from hypothalamic neurons.
- High GnRH secretion and thus LH and FSH release for initiation of follicular growth in the female or inititaion of spermatogenesis in the male
- High LH pulses and amplitudes and thus preovulatory LH surges do not occur unless hypothalamic sensitivity to gonadol estradiol increases. [low frequency GnRH pulses before puberty due to low ovarian estradiol and low hypothalamic sensitivity to estradiol]
Testosterone in males functions to
Increase secretion of LH. And LH increases testosterone.
Testosterone effects
- Increases sperm production
- Stimulates accessory sex gland growth
- Increases male sexual behaviour
- Produces male secondary sex characteristics.
FSH secretion functions to
Stimulate Sertoli cell function
Effects of estrogen on LH before puberty
The increased LH allows follicle to develop to larger stages and produce more estrogen.
Higher estrogen levels eventually start the positive feedback effect and produce LH surge.
LH surge causes an ovulation but no estrus occurs because the animal has not seen progesterone before.
FACTOR INFLUENCING PUBERTY
1. GENETIC COMPOSITION
- Breed differences
- Dairy vs beef animals
- Temperate breeds (Bos taurus) vs Tropical breeds (Bos indicus)
- Crossbreds vs purebreds
Body size
- Body weight
- Nutrition/feeding: extra feed reach early
- Under nutrition: delays puberty
- Flushing initiates puberty
- Degree of fatness: puberty begins after major growth phase (energy required for growth)
- Puberty begins with enough energy is available for reproduction
Nutrition
after puberty male reproductive performance less affected by nutrition than females
- Overfeed earlier than underfeed
- Poor nutrition delayed puberty
- Flushing may stimulate puberty
