Estrous Synchronizatio and Pregnancy Flashcards
how long is the bovine estrous cycle
21 days
how long is a cow in estrus?
12 hours
if you have 100 cows with normal estrous cycles, how many will be in estrus each day?
5 cows per day
what are the potential advantages of estrus synchronization?
increasing estrus detection timing and accuracy AI timing (timed AI, on drug protocols)
what are the advantages of estrus synchronization on a dairy production?
control lactation cycle, control days open
what does days open mean?
the time after the baby is born before rebreeding
what are the advantages of estrus synchronization in a beef production?
reduce breding season, control calving season and production cycles
list and give the function of the hormones of the estrous cycle
- LH: causes ovulation
- FSH: follicle growth
- Estradiol: estrus
- PGF2a: corpus luteum regression
- GnRH: gonadotropin releasing hormone, controls FSH and LH
list the 3 main ovarian events, plus what happens if no embryonic signal detected
- waves of follicles developing- dominant follicle ovulates
- P4: inhibits estrus and ovulation
- Day 10-12 embronic signal, if present
if not pregnant: PGF2a causes regression of CL, dropping P4, P4 inhibtion is removed, the final follicle matures, causing estrus and ovulation
why are there waves of follicular growth?
there need to be additional follicles ready if there is no baby, this growth and regression leads to follicular waves even during pregnancy
at what point in the estrous cycle would a function CL be present?
5-15 days
what if we gave exogenous PGF2a when a functional CL is present (day 5-15)?
CL should regress, and estrus will occur in 48-96 hours
what is the level of response following a single PGF2a injection? break down the percentage
75% in estrus
50% from shot (5-15) days + 25% natural estrus (were in days 15-21 of cycle)
no effect from cows in days 0-5 of cycle, since no CL
what if you use estrus detection and breed for 5 days, then PGF2a shot?
in theory should have 100% in estrus, 25% from observation and 75% from single shot
what if you give PGF2a (0d) plus a 2nd shot of PGF2a at (12d)?
100% in theory, estrus in 48-96 hours
what will PGF2a do if an animal is pregnant?
will cause abortion
why do you need to wear gloves when handling PGF2a?
it is highly fat-soluble so it can be absorbed through the skin
what happens if PGF2a is absorbed through the skin?
will alter normal menstrual cycles, can also cause smooth muscle contractions in individuals who are sensitive to it = fucks up GI tract
what does P4 do?
preparation maintenance of tract for gestation, inhibits estrus and ovulation
what if we provide exogenous P4 source for 10-14 days to cows with normal estrous cycles? and then remove the source?
post-removal = 100% estrus in 48-96 hours (catch them at all points of cycle)
what are some exogenous sources of progesterone?
CIDRs, implants, feed additives
what is the easiest exogenous source P4?
CIDR (controlled internal drug release)
what does GnRH do?
causes release of FSH and LH
when GnRh releases FSH and LH, what follows?
the luteal phase, which is “follicle wars” where follicles compete to be the new lead follicle
when GnRH releases just LH, what follows?
the follicular phase, or ovulation
if you were to give GnRH, wait 7 days, give PGF2a, wait 36-48 hours, and then give more GnRH, what would happen?
first dose of GnRH would eliminate current follicular wave, PGF2a will cause luteolysis, second GnRH will cause the dominant follicle to ovulate, and then you can do timed AI in 8-18 hours
list 4 different advantages of pregnancy determination in dairy cows
- milk production
- DAYS OPEN
- detecting abnormalities
- estrus/breeding efficiency
elaborate on why dyas open is such an advantage of pregnancy determination in dairy cows
great estimate on reproductve efficiency, the goal is to have a cow open for 100-110 days, and you lose $2-$5 per cow per day for each day beyond 90 days open
list 6 advantages of pregnancy determination in beef cows?
- limited breeding season
- pregnancy determination- selection/maintenance
- estimate calving dates
- detecting abnormalities
- estrus/nreeding efficiency
- sire effeciency
if a cow is not pregnant at the end of breeding season, how long until she can potentially produce another calf (her product)
2 years
list 3 methods of pregnancy determination
- palpation
- ultrasound
- blood test (PAG)
when can pregnancy be detected with palpation? can you detect the age or sex of the calf? do you need an experienced technician?
35-50 days, can detect age but not sex, needs an experienced technician
what is the approximate cost per cow of palpation as pregnancy determination, and when do you know results?
$3-$10 per cow, know results immediately
when can pregnancy be deteched with ultrasound? can you detect the age or sex? do you need an experienced technician?
30 days, can detect age and potentially sex, need an experienced technician
what is the approximate cost per cow of ultrasound as a method of pregnancy determination and when do you know results?
$7-$15, know results immediately
when can you detect pregnancy with a blood test, do you kmow the age or sex of the calf? do you need an experienced technician?
28-30 days, can not detect age or sex, do not need an experienced technician
what is the approximate cost per cow of a blood test (PAG) and wen do you know results?
$3-$5 , get results in 1-4 days
what does the PAG mean in a blood test?
pregnancy associated glycoprotein- protein B
where does PAG come from, and when is it measurable until?
calf-induced product- early pregnancy recognition factor (EPRF)measurable around 30 dyas post-fertilization
what are the challenges of using a PAG blood test to determine pregnancy? (3)
- 5-8% false positive or negative results
- present up to 60 days post-calving (from previous pregnancy)
- may remain detectable up to 60 days post-abortion
why is ultrasound a difficult method to detect pregnancy?
cows are big, you need lots of radiation, it’s hard to navigate the instrument in the tract, and you’re already palpating anyway so you might as well just palpate instead
what is the downside of palpation as a method of determining pregnancy?
it will be longer before you can detect pregnancy with just palpation
what is a palpation method that can be done prior to 50 days as a method to determine pregnancy?
fetal membrane slip
what is felt for in a fetal membrane slip?
the placenta; will feel the chorioallentois sliding between your fingers and the uterine wall
when do placentomes completely attach?
40-50 days
what are placentomes made of?
cotyledons and caruncles
what are 2 challenges of fetal membrane slip as a pregnancy detection method?
- it is hard
2. potential damage to fetus/placental attachment
what is a definitive method of palpation as a determination of pregnancy?
placentome palpation
what part of the placentome does the cow contribute?
the caruncle
what part of the placentome does the calf contribute?
the cotyledon
how many placentomes are there in cattle?
60-120
what is the least risky form of palpation as a method of pregnancy determination and when is it performed?
fetal palpation, 3 months or later into pregnancy
where will the fetus be located past 60 days into pregnancy? and why?
right side of pelvic rim; rumen is on the left
what is the natural advantage of using your left hand to palpate?
it will naturally reach to the right towards the repro tract, away from the rumen on the left
where do you go with your hand in AI and why?
go shallow, cervix is usually in the pelvic rim
where do you go with your hand in a pregnancy test and why?
go deep and retract, cow grows from bottom up
