Lecture 1 Flashcards
Describe the mare estrous cycle
• Mares are seasonally polyestrous
Long day breeders (April- October)
Photoperiodic control of reproduction
Length of mare estrous cycle
• Estrous cycle length: 21 days
Length of estrus: 7 days (3 to 12 days)
– Ovulation occurs in the last 24 to 48 hours of estrus
– Dominant hormone: Estrogen (from preovulatory follicle)
– Uterine edema
Length of mare diestrus
• Length of diestrus: 14–15 days
Dominant hormone: Progesterone (causes maximal tone
uterine tone)
Corpus luteum not palpable
Can you palpate the CL in the mare?
no
Goal of advancing the breeding season
Foal born earlier in the year
Sales, futurities, racing advantage
Techniques to advance the breeding season
Shift the transition period to start earlier (same duration)
Shorten the transition period
Protocol to advance the breeding season for the mare
• Start 60 days before desired breeding date • Apply 16 hours of light per day • Intensity (10 foot-candles at mare eye level or mare within 8 feet of 200 watt incandescent light bulb)
Protocol to advance the breeding season for the stallion
• Stallion • Combination light + progesterone or light + progesterone + GnRH or Light + Dopamine antagonist (sulpiride, domperidone)
Use of progestins to advance the season most effective when
• Effective in late transition
How does progesterone advance the season?
• Primes the HPG axis “progesterone priming”
Breeding Options
• Natural cover (mandatory in some breeds i.e.
Thoroughbred)
• Artificial insemination with cooled shipped
semen
• Artificial insemination with frozen semen
• Embryo transfer
• Oocyte transfer or intra-cytoplasmic sperm
injection
What breed is required to do natural cover?
Thoroughbreds
Types of semen to use for AI
Fresh extended semen
Cooled shipped semen
Frozen-thawed semen
Important considerations
• Check with the breed registry for
requirements / paperwork particularly if doing
AI or ET
• Ensure all stallion paperwork is in order
• Requirements for shipping equine semen into
Washington State
Current Coggins test and health certificate
Negative EVA test from the current calendar year or
proof of vaccination
Semen permit number issued by the USDA
Semen evaluation paperwork
Methods for live cover
• Pasture mating (high risk for mares and stallions) • In-hand mating (old approach) • In-hand mating (modern approach) Monitor follicular growth and induce ovulation
• In-hand mating (old approach)
Tease and breed mare every 48 hours
starting on the 3rd day of estrus
Never go beyond 12 days of estrus
• In-hand mating (modern approach)
– Limit # breeding in mares susceptible to endometritis – Efficient use of stallions – Use Minimum contamination breeding technique
Monitor follicular growth and induce
ovulation
– Breed at the time of induction of
ovulation or 24 hours later
• Timing of insemination
• Cooled shipped semen: 24 hours post induction
• Frozen semen
• 2 doses: 24 and 40 hours post induction (pre and postovulation)
• 1 dose: Monitor for ovulation every 6 to 8 hours then AI
after ovulation
Indications for induction of ovulation
• Fixed-time AI
• Reduces the number of
inseminations/breedings
• Synchronization of mares
If you induce ovulation, what size must the follicle be?
35 mm
criteria for the induction of ovulation
- Mare in estrus
- Follicle size
- Uterine edema
hCG
• Glycoprotein (human trophoblast) • LH activity • Can cause anaphylactic reactions • Less efficacious if repeated • Dose: 750 to 300 iu IV, most commonly 2500 iu) • Ovulation in 24 to 48 hours
Deslorelin (SucroMate®)
• Peptide in oil-based controlled release vehicle • GnRH analogue • 1.8 mg deslorelin acetate per mL • 90% of mares ovulate in 41.9±9.4 h
Cooled shipped semen (receiving checklist)
- Check integrity of shipping container - Check paperwork - Check semen quality after insemination and incubation of an aliquot for 10 minutes at 37°C - Minimum dose 150 million motile normal spermatozoa
Frozen semen (receiving checklist)
- Check temperature of dry shipper - Check paperwork - Minimum dose 150 million progressively motile normal spermatozoa