Test 1: 7 nonpregnant cow 2 Flashcards
gonadorelins have the same effect as
GnRH
progestagins have the same effect as
progesterone
(from corpus luteum)
prostaglandins have the same effect as —
PGF2⍺ from the uterus when there is no pregnancy
two ways to manipulate hormones of the estrous cycle of a cow
estrus synch (estrus based insemination)
fixed-time AI
how does estrus synch work in cows
rely on observation and detection of estrus behavior to determine the appropriate insemination time.
how does fixed time AI work in cows
do not require estrus detection. With these programs, females are inseminated on a scheduled time without the need to evaluate behavior.
what part of the estrous cycle can be changed using the fixed time AI
Luteal function control- prostaglandin, progestagin
follicular wave synch- GnRH
ovulation induction- GnRH
how to control luteal function of estrous cycle
give prostagladin- will cause luteolysis → decreased progesterone concentrations
- this decrease in neg feedback will cause ↑ in LH → oocyte maturation, LH surge and ovulation
- estrus will occur 1-6 days after treatment
EDAI and FTAI
— treament is effective in producing luteolysis during approximately 70% of the cycle. Therefore, 70% of females at expected to respond to treatment when that is administered at unknown stage of the cycle.
PGF- prostaglandin
why do 70% of CL respond to external prostaglandin
only responsive 5-7 days after ovulation, if you give med before that will not cause luteolysis
estrus detection and AI
* give prostaglandin (PGF) to everyone and try to cause luteolysis → estrus, then breed
* if not pregnant try again in 14 days
* 90% chance of getting pregnant
how does progestagins control luteal function
- mimics CL
- will supress estrus
- persistant/continuous follicular waves- only use 7 days or else egg gets old
how does GnRH cause follicular wave synch
GnRH treatment results in an LH surge and decreased estradiol, caused by luteinization or ovulation of the dominant follicle. Release of estradiol’s negative feedback of the HPG axis results in an FSH-surge acompanyed by the emergence of a new follicualr wave aproximately 2 days after GnRH treatment.
GnRH treatment results in an —, caused by luteinization or ovulation of the dominant follicle. Release of estradiol’s negative feedback of the HPG axis results in an — acompanied by the emergence of a new follicualr wave aproximately — after GnRH treatment.
LH surge and decreased estradiol
FSH-surge
2 days
GnRH’s efficacy in synchronizing follicular wave emergence is affected by the developmental stage of the dominant follicle. If the follicle is unresponsive to —, then GnRH will not result in synchronous wave emergence.
LH
how does OvSynch AI protocols work
Initially, cows are treated with GnRH to synchronize follicular wave emergence. After 7 days, cows are treated with PGF to lyse the CL. A second dose of GnRH is administered 56 h after PGF treatment, at which point a dominant follicle ready to ovulate should be present. Cows are then inseminated 16 hours after the second GnRH treatment (or 9 days after the first GnRH treatment).
