Bovine - Female Repro Physiology Flashcards
What are the important endogenous hormones of the estrous cycle?
GnRH, LH, FSH, Estrogen/estradiol, inhibin, P4, PGF2-alpha
What does GnRH stand for?
Gonadotropin Releasing Hormone
What is the origin and target of GnRH?
it originates in the hypothalamus and targets the anterior pituitary
What is the function of GnRH?
stimulate production and release of gonadotropins (FSH and LH)
What system does GnRH utilize?
the hypothalamo-hypophyseal portal
What does FSH stand for?
follicle stimulating hormone
What is the origin and target of FSH?
originates in the anterier pituitary and targets the ovary
What is the function of FSH?
stimulate follicular recruitment and early follicular development - increases estrogen
What does LH stand for?
Luteinizing hormone
What is the origin and target of LH?
It originiates in the anterier pituitary and targets the theca and granulosa cells of ovarian follicle (especially the dominant) and corpus luteum
What is the function of LH?
it aids in follicular maturation, causes ovulation, and aids in maintaining the CL - it causes an increase in androgens
What happens to the androgens (testosterone) that LH influences the thecal cells to produce?
They are essentially pushed from the thecal cells to the granulosa cells to be converted into estrogens (estradiol)
What is the origin and target of etrogen/estrodial?
It originates in the follicles and targets the pituitary and hypothalamus and reproductive organs
What is the function of estrogen/estradiol?
It promotes GnRH release from the hypothalamus and alters FSH/LH ratio from pituitary
What is the origin and target of inhibin?
It originates in the granulosa cells in the ovarian follicle (dominant) and targets the anterior pituitary (negative feedback)
What is the function of inhibin?
suppresses the production and secretion of FSH
What is the origin and target of progesterone?
It originates in the corpus luteum and placenta and targets the hypothalamus and uterus
What is the function of progesterone?
It suppressess the secretion of GnRH from the hypothalamus (surge center) and allows for maternal recognition and maintenance of pregnancy
What is the origin and target of prostaglandin?
It originates in the endometrium and potentially the ovary and targets the corpus luteum
Where is prostaglandin excreted from the body?
the lungs
What is the function of prostaglandin?
lysis of the CL
What does prostaglandin utilize to move throughout the body?
it utilizes the utero-ovarian vascular countercurrent diffusion
What male structure is the utero-ovarian vascular countercurrent exchange homologous to?
the pampiniform plexus
What is the bovine cyclicity like?
polyestrous
How many eggs does the bovine ovulate in one cycle?
one
Do cattle go through menopause?
no - the bovine continues normal cyclicity throughout its life unless it is inhibited by disease or pregnancy
What is the length of the estrous cycle?
21 days (17-24)
What are the phases of the estrous cycle?
the follicular phase and the luteal phase
What happens during the recruitment stage of the estrous cycle (hormones)?
The tonic center releases GnRH to act on the anterior pituitary
The anterior pituitary releases FSH and LH to act on the ovary; more FSH is released than LH because FSH is needed for recruiting follicles
The recruited follicles release estradiol
The estradiol communicates to the surge center - ‘Hey bro, we need to make more, we are still working on growth here’
What happens during the selection phase of the estrous cycle?
GnRH is released from the tonic center to work on the anterior pituitary
The anterior pituitary releases FSH and LH; more LH is released in this stage because follicles are no longer needed to be recruited, they need to grow
Inhibin is released by the ‘selected’ follicles to tell the anterior pituitary ‘My dude, we need more LH, not FSH. WE NEED TO BE BIG AND STRONG’
Estradiol is still being released by the follicles to tell the hypothalamus ‘Keep that GnRH coming, we aren’t done yet.
What happens during the dominance stage of the estrous cycle (hormones)?
GnRH, released from the tonic center, continues to work on the anterior pituitary.
The anterior pituitary releases FSH and LH: this is when there is the highest surge of LH because the follicles gotta grow
The dominant follicle is releasing inhibin to work on the anterior pituitary to decrease the FSH secretion; ‘I am big brother, I eat all nutrients, no little bros please’
Estradiol is released from the dominant follicle to stimulate continued release of GnRH for further growth
Explain how estrogen provides negative feedback when progesterone is present.
When progesterone is present, even though the estradiol is telling the hypothalamus ‘bro, we need more,’ the progesterone (the gate keeper) is telling the hypothalamus ‘Nah, we gucci fam.’ After a while, estradiol and inhibin throw up the white flag and let progesterone win. The dominant follicle goes through atresia because there is no GnRH surge to push the follicle to ovulate.
Explain how estradiol provides positive feedback when progesterone is not present.
When progesterone is not present, the estradiol keeps communicating to the hypothalamus saying ‘hey we are producing enough estradiol, lets get things going.’ The hypothalamus notices that progesterone is no longer present and is like ‘okay, lets do this.’ There is a GnRH surge that increases the LH concentration, hopefully causing ovulation.
What stages occur during the follicular phase?
proestrus stage and estrus
What stages occur during the luteal phase?
metestrus stage and diestrus stage
What is the follicular phase?
It is the period from regression of the corpus lutea to ovulation
In regards to the estrous cycle, what is the length (percentage) of the follicular phase?
it is relatively short - 20%
What do the primary ovarian structures do during the follicular phase?
the dominant follicle grows and the CL regresses
What hormone is involved in the follicular phase?
estrogen
When does proestrus occur?
after diestrus or anestrous, preceding estrus
When, hormone wise, does the follicular phase begin?
when progesterone declines from resulting luteolysis
During the follicular phase, there is a transition from __________ dominance to _________ dominance.
progesterone to estrogen
What is estrus a period of?
sexual receptivity
What behaviors do cattle exhibit during estrus?
increased locomotion, vocal expression, nervousness, and mounting
How long does estrus typically last?
16 hours on average
When does ovulation occur in regards to standing estrus?
12-16 hours post standing estrus
What is the average time from standing estrus to ovulation?
approximately 30 hours
When is the highest estrogen period?
during estrus
What are some ways to detect if a cattle is in standing estrus?
put paint stic, chalk, or some detection device on their tails that will indicate they have been mounted
When is the luteal phase?
it is the period from ovulation of dominant follicle to the regression of the corpus lutea
How long, in regards to the estrous cycle, is the luteal phase?
it is the longest part of the estrous cycle - 80%
What is the dominant structure during the luteal phase?
the corpus luteum
What is the primary hormone of the luteal phase?
progesterone
What is happening physiologically during the luteal phase?
follicles are continuously growing and +/- regressing through the luteal phase, however, do not produce enough estrogen to proceed to the follicular phase
When is metestrus?
the period between pvulation and formation of functional CL
Early on in the metestrus stage, what are the hormone levels like?
progesterone and estrogen are low
What is lutenization?
When the newly ovulated follicle must undergo cellular and structural remodeling
What cellular changes happen in lutenization?
granulosa and theca cells turn into luteal cells
What is the longest stage of the estrous cycle?
diestrus
What physiologically occurs during diestrus?
the corpus luteum is fully functional and production of progesterone is high
What does high progesterone levels prime the uterus for?
to provide a suitable environment for conception
When does diestrus end?
it ends at luteolysis or termination of pregnancy
What is the size of a dominant follicle?
an 8mm follicle
What is the size of a pre-ovulatory follicle?
16-18mm
What is the purpose of using exogenous drugs in reproduction?
treatment of disease processes, control the estrous cycle, and alter the estrous cycle
What disease processes do exogenous drugs treat?
cysts, pyometra, abortificant
How do exogenous drugs control the estrous cycle?
inhibit or induce estrus behavior
How long is the corpus luteum susceptible to prostaglandin?
between days 5 to 17 of the estrous cycle
What drug is lutalyse?
dinoprost tromethamine - natural PGF2-alpha
What drug is estrumate/estroPLAN?
cloprostenol sodium - analouge PGF2-alpha
What uses is Lutalyse indicated for?
estrus synchronization, treatment of unobserved estrus, pyometra in cattle, or abortion of feedlot and other non-lactating cattle
What uses is estrumate indicated for?
terminate pregnancies resulting from mismatings, treat certain conditions associated with prolonged luteal function, and estrus synchronization
What uses is estroPLAN indicated for?
luteolysis in cycling dairy cows and beef cows, and estrus synchronization
GnRH only works when?
when a dominant follicle is present, the hormone receptors are present, and progesterone, estradiol, and inhibin are present
What brand name products are GnRH?
Cystorelin, Factrelin, Fertagyl, gonabreed
What use is Cystorelin indicated for?
the treatment of ovarian follicular cysts
What uses is Factrel indicated for?
treatment of ovarian follicular cysts in cattle, and may be used with lutalyse to synchronize estrus cycles to allow fixed-time artificial insemination in lactating dairy cows
What uses is Fertagyl indicated for?
treatment of cystic ovaries in dairy cattle and for use with estrumate to synchronize estrous cycles to allow for fixed time artifical insemination in lactating dairy cows
What uses is Gonabreed indicated for?
the treatment of ovarian follicular cysts in dary cattle and for use with estroPLAN to synchronize estrous cycles to allow for fixed time artificial insemination in lactating dairy cows and beef cows
What are progesterone products?
MGA (melengestrol acetate) and CIDR (controlled internal drug release)
What uses are CIDR indicated for?
synchronization of estrus in beef cows, replacement beef, and dairy heifers, with an injection of lutalyse
induction of estrous cycles in anestrous lactating dairy cows
advancement of first postpartum estrus in suckled beef cows
advancement of first pubertal estrus in replacement beef heifers
What use is MGA indicated for?
to suppress estrus in heifers for slaughter or for synchronization purposes in heifers
MGA use should not exceed how many days?
24
What is folltropin-v (FSH) used for?
typically only for superovulation for ART (it is expensive) …I think ART stands for animal reproduction technologies
What is lutropin-v made out of and why would it be used?
it is porcine pituitary extract to get LH activity without needing FSH
What kind of activity does HCG have?
the same activity as pLH (lutropin-v)
What properties does equine chorionic gonadotropin (eCG) and pregnant mare serum gonadotropin (PMSG) have?
it has both LH and FSH properties but mostly FSH activity in the cow
What is estradiol (injectable) used for?
to change the ratio of FSH to LH - IT IS ILLEGAL
