Manipulating the Estrous Cycle Flashcards
What must you know in order to manipulate the estrous cycle?
knowledge of the function and timing of the major regulatory hormones and ovarian structures
Ovulatory agents
induce ovulation
What must you have in order to use ovulatory agents?
a pre-ovulatory follicle (30-35 mm +)
What are some commercially available ovulatory agents?
-Human chorionic gonadotropin (hCG) - acts as LH
-Deslorelin (sucramate) - GnRH analog stimualtes release of LH (acts on the anterior pituitary)
Are ovulatory agents effective?
yes, essentially they are effective in knowing once given, the mare will ovulate in 48 hours
Advantages of giving ovulatory agents before breeding:
shorter interval for fertilization once bred
Disadvantages of giving ovulatory agents before breeding:
could ovulate too early
Advantages of using ovulatory agents:
-decrease incidence of 2 covers/cycle
-ovulation timed to sperm availability (“appointment breeding”)
-synchronize mares (ovulate at the same time-important for embryo transfer donors and recipients)
Disadvantages of using ovulatory agents:
-some risk of it not working
-cost (hCG costs less than Des-)
-increase twinning (double ovulation)
-hCG may lose effectiveness with time (mares can make antibodies and have an anaphylactic reaction)
Luteolytic agents
a normal cycle occurs, they lyse the CL by PGF2alpha from a non-pregnant uterus
-mimic action of natural PGF2alpha
What is a common type of luteolytic agent?
synthetic prostaglandins
Commercial products of luteolytic agents:
-lutalyse - some side effects (sweating, uterine contractions, acting collicy, etc.)
-estrumate - milder side effects
Primary purpose of luteolytic agents:
lysis of CL to shorten diestrus
When should luteolytic agents be administered?
about 5-6 days post ovulation
What must be present for luteolytic agents to work
the CL