ruminant breeding mgmt Flashcards
Bovine
- Normal cycle length
- Estrus
- Metestrus
- Diestrus
- Proestrus
- Normal cycle length = 21d
- Estrus = 24h
- Metestrus = 3-4d
- Diestrus = 14d
- Proestrus = 2-3d
Purpose/goal of DAIRY versus BEEF breeding management versus
DAIRY
- purpose = year-round production of milk
- goal is to maintain a 13-month calving interval per cow
- cow is pregnant for 9mo + VWP for 2-2.5mo, bred within 1mo of VWP = ~13mo
BEEF
- purpose = sale of calves @ weaning
Voluntary Waiting Period (dairy cows) - define, purpose, duration
set amt of time post-partum than an animal is not being bred - usually around 60-80d
- allows uterus to recover, allows cow to achieve (+) energy balance & resume cycling
- 90-95% of cows should be inseminated within 30 days of VWP (if combining estrus detection w/ timed AI)
What is used to determine best time to perform artificial insemination, and/or to confirm females are in heat?
Detection of estrus
Purpose of teaser bull
to “tease” female to enter heat/estrus for AI, without the bull actually penetrating
Two primary causes of poor repro performance & low repro efficiency in dairy cattle
- poor efficiency in heat detection (100 cows in heat, only detect 50)
- poor accuracy in heat detection (detect 50 cows in heat, only 30 are actually in heat)
Results of inadequate heat detection in dairy cows
- production losses (longer calving intervals, lower net milk lifetime production)
- lost $$ on breeding cows which are actually unsuitable for insemination
- potential inappropriate culling of normal cows
Pregnancy Rate equation:
PR = HDR * CR
- HDR = Heat Detection Rate
- CR = Conception Rate
e.g., 100 cows in herd eligible for breeding, but only 35 cows are detected submitted for AI. HDR = 35%. Then, only 14/35 cows become pregnant. -> CR = 40%. -> 35% * 40% = 14%.
If doing timed AI, you are not using HDR most of the time -> CR will then = PR
AM-PM rule
Ruminants only
- if female observed in estrus in AM, will breed her via AI in PM (and vice versa)
recall: estrus lasts 24h
2 ways the estrous cycle can be controlled via drugs?
Shorten Luteal Phase - rx via prostaglandin (-> CL lysis) - Dinoprost (Lutalyse®); Cloprostenol (Estrumate®)
Lengthen Luteal Phase - rx via progestin (-> neg. feeback on pit. gland)
Other: GnRH agonist -> resests follicular wave by stimualting LH/FSH from anterior pituitary. Guarantees follicular wave formation
cows must be on DIESTRUS (CL present) for prostaglandin administration!
Where is prostaglandin (PGF2alpha) produced? How does it reach the ovary in ruminants/porcine animals compared to other species??
Uterine endometrium -> travels to ovary (to lyse the CL) from: uterine vein -> picked up by uterine artery (stays local – lower dose needed for dinoprost).
Other spp: prostaglandin must enter systemic circulation from uterine vein, travel to heart, lungs, aorta, etc. -> -> uterine artery (higher doses needed of dinoprost)
Importance of prostaglandin administration during uprising of follicular wave
Allows for lysing of the CL AND for follicular wave to mature (rather than having to wait for another wave to develop) -> dominant follicle -> ovulation
How does exogenous progestin (synthetic progesterone) work?
trick hypothalamus/pitutary that a CL is present (via negative feedback/P4) -> luteal phase lengthened
does not actually lengthen lifespan of CL! CL has definite lifespan.
MGA
orally active progestin - feed additive; use for synchronization = extra-label use
CIDR
Controlled Intravaginal Drug Release
- infused w/ progestins which are absorbed through vaginal mucosa
Timed AI Protocols - After exogenous prostaglandin administration, how does exogenous GnRH guarantee synchronization?
Assuming that there was a CL present, PGF admin lysed that CL -> no active CL present when GnRH was given + LH release still occurs -> forces ovulation closer to the time of AI
OV-Synch
Commonly used timed AI in dairy cows
- GnRH given prior to timed AI
makes sure dominant follicle release oocyte as close to AI as possible
CO-Synch
Commonly used timed AI in beef cows
- used over OV-Synch b/c less handling – beef cattle are not as used to handling events as dairy cattle (b/c no milking)
- GnRH given @ same time as timed AI
Why might one add CIDR between first GnRH and PGF administrations
recall: CIDR = controlled intravaginal drug release - progestin (P4) absored thru vaginal mucosa
- P4 signals negative feeback to hypothalamus on GnRH release = NO LSH/FSH release. Giving CIDR may help prevent….////
The Male Effect in SRs
intro of a ram or buck into group of transitional period ewes / does to activate pre-ovulatory LH surge & induce a silent ovulation (brings them out out of Anestrus period earlier than normal, so NO prior luteal phase to prime hypothalamus for P4 = no estrous behavior). There is NO breeding during this period (she is “sterile”).
- 50% of ewes & 70% of does will develop an (abnormal) CL with Male Effect, even with silent ovulation, -> the abnormal CL will undergo premature luteolysis -> priming of hypothalamus for P4 occurs -> -> normal estrous behavior will begin to occur and she will undergo normal heat cycle.
to skip the silent ovulation/expedite breeding, give progestin
