Bovine Breeding Management Flashcards
what is the length of gestation in cows
280 days
what is the period of involution in cows
50 days
what is the natural length of the cycle in cows
21 days
how many heat cycles do producers have to get cows pregnant and meet their economic target of 1 calf/cow/13 months
3
The duration of estrus and # of events during estrus in heifers is higher/lower than in cows
higher
The duration and signs associated with estrus are higher/lower in high vs low producing cows
lower
overall, the duration of standing estrus over the entire estrus period in cows is under
30 seconds!
on average, estrus in cows lasts
12-18 hours
what is Heat Detection Rate (HDR)
proportion of cows detected in estrus
what is Insemination Risk
cows submitted for AI that are in estrus (proportion of AI eligible cows detected in heat)
what is Conception Risk
probability that AI results in pregnancy (proportion of breedings that result in pregnancy)
what is the 21-day pregnancy risk roughly equal to
HDRxCR
what is 21-day pregnancy risk
proportion of open cows that become pregnant every cycle
how many days after ovulation does the CL become mature/responsive
7
how quickly does PGF2α cause luteolysis in a mature CL in cows
1 day
PGF half life is (seconds/minutes/hours/days)
minutes
GnRH is a chain of amino acids. What does this mean
if you ingest it, it is digested
What hormone, when given exogenously, causes blood/milk levels LOWER than the endogenous hormone
progesterone (P4)
what is the BIGGEST challenge for bovine producers in getting cows pregnant
DETECTION of HEAT
what are factors that can confound heat detection in cows (5)
confinement, lameness, flooring, comfort, negative energy balance
ovulation occurs in cows how many hours after standing heat
27h later
after ovulation, the ovum lifespan in cows is
6-8h
capacitation of sperm occurs how many hours after ejaculation
10
what is the basis of activity monitors for heat detection
there is a huge spike in activity the day a cow comes into heat
what are the limitations to PGF2α for estrus synchronization in cows (3)
1) not all will respond (66% apparent response)
2) need to be able to detect a mature CL
3) variable time to ovulation depending on the phase of the wave in individual cows
T/F PGF2α allows for timed AI
F (it does not control follicles so it cannot)
the average interval from PGF2α to estrus detection is
3 days
describe OvSynch
1) give GnRH on day 1 to stim follicular growth
2) give shot of PGF2α to lyse any CL on day 7
3) give GnRH again 2- 2.5 days later
4) timed AI within the next day
T/F OvSynch allows for timed AI
T
what is a key step to improve fertility during OvSynch
ovulating after the first shot of GnRH so that there is a CL producing progesterone during the follicular growth before the dose of PGF2α
we want to inseminate ~ how many hours after giving the second dose of GnRH in an OvSynch program
16
what is the effect on OvSynch if we start 1-4 days after the last heat
failure to synchronize new follicular wave
what is the effect on OvSynch if we start 13-17 days after the last heat
spontaneous luteolysis and ovulation before timed AI
what is the effect on OvSynch if we start 18-21 days after the last heat
unresponsive CL when we give PGF
how many days after the last ovulation is ideal to start OvSynch
5-12 (but goal of presynching is to get them at 6-7 days)
what are the two methods of pre-synchronizing the estrus cycle before starting OvSynch
1) Pre-Synch: 2 PGF, 2 weeks apart, 2 weeks before OVS
2) Double OvSynch: Ovsynch -> no AI -> 7d -> OvSynch -> timed AI
what is the goal of pre-synchronization
start OvSynch when the cows are 6-7 days after the last ovulation
what can be used to stimulate ovulation in anestrus cows
CIDRs (intravaginal progesterone)
what 2 uses can CIDRs be used for
1) bring cow out of anestrus
2) stimulate turnover in cystic cows
what is a potential side-effect of using CIDRs in cows
if used for longer than 14 days, it produces a persistent dominant follicle (cyst) -> reduced fertility
