repro Flashcards
sheep and goats are ______ breeders
short day
how do you do in season synchronization of estrus?
- prostaglandin injection (estrumate or lutalyse)
- external progesterone (CIDR, MGA)
how does prostaglandin work to synchronize estrus?
PGF2alpha causes CL to regress, resulting in drop of blood P4, initiating onset of estrus
use in diestrus
will be in heat 24-48h after injection
only works when naturally cycling – need CL to be there already
what is the two dose program for estrumate? why do we use it?
we don’t know who is at what stage in the esturus cycle. approx 70% will be in diestrus if you inject the entire herd. in order to get the remaining 30%, do 2 doses
inject estrumate to everyone, then 11 days later, inject everyone again
how does external progesterone work to synchronize estrus?
prevents decrease in P4 that initiates estrus = blocking onset of heat
what is a CIDR and how does it work to synchronize estrus?
controlled intravaginal drug release (natural P4)
will prevent estrus when in, and after taking out, 24-48h there will be heat
leave in ewe for 10-18 days during in season
in large groups, stagger CIDR removal
introduce males 12-24h after CIDR removal
what does pregnant mare serum gonadotropin (PMSG) do when you administer it at CIDR removal?
increases ovulation rate, increases synchrony within the group (tightens ovulation window to 12-18h for everyone)
essential for AI or ET programs, essential for out of season programs
what is MGA and how does it work to synchronize estrus?
melengesterol acetate –> in feed progesterone
ewes will come into heat 36-48h after last MGA feeding
intro rams at 36h after last feeding
variable results - inconsistent estrus and conception rates - not used often anymore
it’s costly, so more cost effective in large groups of ewes
how can you synchronize estrus out of season?
progesterone + PMSG
day length manipulation
true or false: there is a genetic selection for ability to breed out of season
true
you should keep replacement lambs from ewes that lamb out of season
how do you use progesterone + PMSG to synchronize estrus out of season?
P4 for at least 7-9 days –> causes almost normal follicles to develop
PMSG needed to cause ovulation (use GnRH in goats)
how do you use daylight manipulation to synchronize estrus out of season?
need expensive barns!
confine to light tight barn, expose to long day light for 8-12 weeks, then expose to short day length for 8-12 weeks
must be a min of 8h difference in day length
expose rams/bucks to same protocol
how can you synchronize estrus in the transitional period?
- progesterone (CIDR or MGA)
- ram/buck effect (use teaser male before putting intact males in)
what is the traditional breeding program? i.e, when is the normal breeding season/program for ewes/does?
fall breeding, spring lambing
highest natural prolificacy, ideal time to use AI and ET, often low market price for finished lambs/kids, more probs with parasites in lambs/kids
when is out of season breeding?
spring/summer breeding for fall/winter lambing/kidding
target high market prices, often more expensive to produce
