Manipulation of Estrous Flashcards
1
Q
What is synchronization of estrus?
A
- Timing the onset of estrus (heat behavior) and the events leading to ovulation of fertile oocytes is determined by human actions
- A group of females display estrus (heat) and ovulate fertile oocytes within a few hours of each other
- Purpose of estrous synchronization is to allow group-mating (usually using artificial insemination)
2
Q
What does the hypothalamus do for the estrous cycle?
A
- Releases small peptides - GnRH is important
- Causes pituitary release of FSH and LH
3
Q
What are the actions of GnRH
A
- Causes release of Luteinizing hormone (LH)
- Ovulation or luteinization
- Initiates new follicular wave
- CL formation
4
Q
What does the Corpus Luteum do?
A
- Produces progesterone to prepare the uterus for the egg
- P4 acts on the brain to override estrogen to prevent estrus behavior
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5
Q
What are the actions of Progesterone?
A
- Secreted by CL
- Suppress estrus and ovulation
- Pregnancy maintenance
- “Jump starts” anestrus females
- We control the estrous cycle by controlling the progesterone level (CL)
- Regu-Mate, MGAA, and CIDR inserts
6
Q
What is the role of the Uterus?
A
- Produces PGF2a when NOT pregnant by the endometrium
- Lyse the CL and initiates the process that leads to ovulation
7
Q
Why is synchronization of estrus done in cows?
A
Enhance the utilization of artificial insemination
8
Q
What methods are used to synchronize Ovine estrus?
A
- Prostaglandin F2a
- Progestogen alone (or with hCG + eCG)
9
Q
How can gilts be rushed to puberty with hormonal treatment?
A
- Gilts should be within 1 month of natural puberty (6-7 mo)
- Give single injection of a combination of eCG and hCG
- 50-70% of prepubertal gilts will exhibit estrus within 7 days
- NOT bred on puberal estrus
- Will not result in predictable timing of estrus in gilts that are already cycling
- Can inject PGF2a 18 days after hCG to tighten estrus synchrony of the subsequent cycle
10
Q
How can estrus be synchronized in gilts that are already cycling?
A
- PG600-PG strategy does NOT work
- swine CL is resistant to PGF2a until late in diestrus (> d12)
- Abortifacient activity of PGF2a - pen mate gilts for 3 weeks and then give PGF2a two weeks later
- CL will lyse - ⇣P4 ⇢ embryo resorption ⇢ return to estrus in 4 - 5 days
- Can feed progestogen for 18-19 days - will return to estrus in 4 - 5 days
11
Q
How is estrus manipulated in horses?
A
- Manipulating ONSET of estrus is easier than predicting//synchronizing ovulation
12
Q
How does lactation affect the estrus cycle in swine?
A
- Estrus in lactating sows is usually controlled by weaning the piglets
- STRONG lactational anestrous
- Delayed return to estrus seen in some genetic lines
- Strategy:
- PGF2a w/n 24h of farrowing (parturition)
- PG 600 at time of weaning
13
Q
How can Estrus be manipulated in Equines?
A
- Manipulating onset is easier than predicting/synchronizing ovulation
- Compared to bovine/ovine - much longer estrus period (4-7 days)
- Variable timing of ovulation relative to estrus
- Therefore - still need to palpate/ultrasound ovaries
- Estrus manipulation/synchronization benefits:
- Efficient use of stallion
- Ability to schedule breeding
- Synchronization of recipients for ET
- Approved Treatments:
- PGF2a
- Progestogen (Regu-Mate)
14
Q
What are the possible side-effects of PGF2a in mares?
A
- Onset 5-60 minutes after injection
- Sweating
- Colic (⇡ GIT motility)
- ⇡ Heart rate
- weakness and ataxia
15
Q
How does PGF2a alter the estrus cycle in the mare?
A
- Need lower does than cattle
- CL can be lysed in late estrus during diestrus (≥5 days after ovulation)
- Side effects can be pronounced
- 2 injections 14 days apart
- 60% in estrus w/n 4 days
- 90% in estrus w/n 6 days
- Ovulation 2-12 days after last injection
- mares with larger follicles at time of injection will ovulate sooner than mares with small follicles
