Sheep and Goat Breeding Programs Flashcards
age at puberty for sheep vs goats
sheep = 4-7m
goat = 3-7m
age at first breeding for sheep vs goats
both = 6-8m
source of P4 during pregnancy for sheep vs goats
sheep = CL and placenta after day 75
goat = CL only
gestation length for sheep vs goats
sheep = 144-151d
goat = 147-155d
pseudocyesis for sheep vs goats
sheep = uncommon
goat = common
length of estrus cycle for sheep vs goats
sheep = 17d
goat = 21d
ovulation rate for sheep vs goats
sheep = breed dependent
goat = most breeds are prolific
behavioural estrus for sheep vs goats
sheep = anorexia, vulvar swelling, small amounts of mucus, will follow ram
goat = restless, wag tail, vocalize, swollen vulva, clear vaginal mucus, follow buck
do sheep or goats have more subtle estrus behaviour
sheep
what is the long day breeding based on
based on the decreased day length causing increased melatonin secretion…. this stimulates the hypothalamus to secrete GnRH after about 45d (early august)
the first estrus is _____
silent. so they are fertile but non-behavioural
how long is the ovulatory season
4 months
when do females give birth naturally
spring
when are lambs/kids weaned
60 days
when are replacement females bred
7 months
what is the reason for implementing accelerated lambing programs
-decreases/eliminates the open and dry period
what is required for successful accelerated lambing programs
-out of season breeding
-needs good organizational management
-two program options (3 in 2, cornell star)
why should we manipulate the estrus cycle in small ruminants? (4)
to shorten the lambing window
* Synchronization can yield a shorter breeding period, which means a shorter lambing period
* Easier to observe females, manage dystocias
* Easier to observe neonates, better manage
* More uniform crop of animals for marketing
what is the benefit of manipulating the estrus cycle? (3)
- Year-round milk production for dairy farms
- Off-season markets (higher prices)
- Employ accelerated lambing systems (more efficient use of animals)
what are some methods of hormones for estrus synchronization
-prostaglandin injectable (off label for sheep and goats)
-progesterone (CIDR) (approved for sheep, off label for goats)
-progesterone (MGA); given in feed, only for meat animals
-eCG or PMSG injectable; stimulates FSH and LH
what is required for ovulation in the anovular period
injetion of eCG or PMSG
two names of prostaglandin drugs
estrumate, lutalyse
what is the one criteria for a prostaglandin program in the ovulatory program to work
will only work when females have a CL
what is the purpose of the prostaglandin program during the ovulatory season
to synchronize estrus
how does a long CIRD program work during the ovulatory season
put CIDR in for long enough that it eventually becomes the ONLY P4 source for the sheep. it acts like a CL
this will allow all females to come into estrus at the same time
when does a male need to be introduced in a CIDR program
24h after CIDR removal
what is an extra step that is needed for the short CIDR program compared to the long CIDR program
concept is the same but we MUST inject prostaglandin 1-3 days before we have to remove the CIDR to eliminaete any CLs that are still present
what needs to occur for a CIDR program during the ANOVULATORY OR TRANSITION period?
-insert CIDR like the short CIDR program
-inject a prostaglandin 1-3d before CIDR removal IF you suspect any animals are still cycling
-required to inject eCG/PMSG at the time the CIDR is removed to induce ovulation
when do you introduce males when using MGA?
males introduced 24-26h after feeding stopped
what is the difference between MGA program during ovulatory season vs anovulatory season
ovulatory = eCG 8h after last feeding is OPTIONAL. and feed for longer
anovulatory = eCG 8h after last feeding is REQUIRED. dont have to feed for as long
when is the male effect good vs bad
best during transition season, worst during ovulatory season, variable during anovulatory season
what does the introduction of males cause
silent heat…. CL regresses prematurely and then a behaviourally normal heat follows
when do teaser rams need to be removed and replaced with fertile rams?
no later than 14d after teasers are introduced
when is the teaser effect used
in the first few weeks prior to the expected onset of natural breeding season. no exposure to rams at least 30d prior
how does the teaser effect work
rams and teasers give off pheromones which stimulate non sexually active ewes to ovulate within 2-3d of joining with teasers
what are the two ways ewes will respond to teasing
- show behavioural estrus and mate with rams ~3w after teaser introduction (early mating group)
- or display estrus and mate some 4 weeks after teaser introduction (late mating group)
what is the dormitory effect
occurs during the transition season. its when some animals start to cycle, ~25% of the anestrus group will cycle as well. the rest will respond within a few weeks
what is the expectation of # of ewes lambing from FIRST cycle breeding success?
75%
what are some factors affecting success in small ruminant breeding programs/?
-some breeds are more seasonal than others
-ram to ewe ratio is critical
-CIDR losses
-MGA and feed management
-nutrition (BCS, flushing)
-timing of male intro for synch programs (if too early, can be bred before ovulatory window)
