equine breeding management Flashcards
How long does semen live for?
Depends on the stallion and handling, but on average:
Fresh = 2-5 days – very stallion dependent
Cooled-shipped = 48 hours
Frozen = ~12 hours
How long do oocytes live after ovulation?
6-12 hours
methods to determine where a mare is at in her cycle
Records
Teasing
Vaginoscopy
Palpation
Ultrasound
how will mare behave for teaser in diestrus?
Mare is NOT receptive
Squeals
Kicks out
Pins her ears
how will uterus feel during diestrus?
you feel uterine tone
what will we see on ultrasound during diestrus
-no uterine edema
-follicles
what will you see on vaginoscopy and palpation during diestrus (looking at cervix)
Looks pale (“white”)
Located in central vagina
On vaginal palpation you feel:
Pencil-like structure
Tight
what should we do to induce estrus?
Manipulate the luteal phase
How can we shorten the luteal phase?
Prostaglandin injection
> causes luteolysis
prostaglandin injection side effects
Sweating, colicky, diarrhea
how long after prostaglandin injection should we see heat
Should come into heat in 2-5 days
more behaviour during estrus when teased
Urinating
Winking
Lifting her tail off to the side
Squatting
how does uterus feel during estrus
Uterus feels flaccid
what do we see on ultrasound during estrus
Uterine edema (grade 1-2)
-no CL
-follicle
what will we see on vaginoscopy during estrus
Soft, relaxed cervix, edematous
how fast does a follicle grow during a mare’s heat? what other changes?
Grows approx. 3mm/day
Becomes Softer
More irregular shape
Bright border
Follicle size at Ovulation
Depends on:
History
Breed
Miniature: 35 mm
QH, Arabian: 38-42 mm
TB, Standardbred: 40 mm or more
Warmblood: 48 mm or more
Draft: 55 mm +
When to order semen?
Stallion owner needs to know how many mares need a dose prior to collection or if they need to collect at all that day
Then need to collect stallion, process the semen & ship it
This takes time
call in advance
when is it acceptable to induce ovulation?
when follicle is large enough diameter
Good uterine edema
how do we induce ovulation? how long after will it occur?
hCG (human chorionic gonadotropin)
>Acts like LH
Deslorelin acetate
>GnRH analogue
Should ovulate within 48hrs
what is a breeding dose of sper?
A breeding dose is 500x106 progressively motile sperm
waht should sperm concentration be when we cool it for shipping
Want the concentration of dose to be 25-50x106/ml
when we cool it for shipping
Dilute semen with extender in a ratio of 1:3 to 1:5 (typically)
what is semen extender? what does it do?
Often milk based (or similar) with sugars, proteins, lipids & antibiotics
Goal is to:
Provide nutrients for the sperm
Counteract harmful by-products from sperm metabolism
Maintain appropriate pH and osmolality
Protect from cold shock
Prevent bacterial growth
Preparation of sperm for cooling & shipping
Sterile disposable plastic bags, conical tubes or syringes
Controlled rate of cooling (~0.05oC/min) to 5oC (takes ~10 hours)
Cooling slows sperm metabolism > makes them live longer
how do you perform AI?
No need to warm up the dose Clean mare’s perineum well
Sterile glove & AI pipette
Pass through the cervix
Deposit dose in the uterus
Evaluate semen under microscope
what do we do after AI?
Ovulation Check
how do we do an ovulation check after AI? outcomes?
-1-2 days after AI, repeat the ultrasound to confirm ovulation
-identify presence of a corpus luteum
If not - ? Option to breed again?
Depends on how long it takes semen to arrive
Note she may ovulate soon anyway – check size, shape and softness of follicle, amount of endometrial edema
mare pregnancy rates with AI?
Expected Results
50-78% pregnancy rates on first cycle
85-95% seasonal conception rates
Not different from AI with fresh extended semen
Stallion dependent
Some stallion’s semen does not survive cooling well
how do we diagnose pregnancy in the mare?
Pregnancy Diagnosis
14 day pregnancy ultrasound
26 day pregnancy ultrasound – heart beat check
45 day
60 day
Autumn check
Live cover without palpation/ultrasound; how do we manage?
Live cover without palpation/ultrasound
Put them in a field together and do their thing; or
Determine estrus/receptivity with teasing
Breed 2nd day of estrus and EOD until “out”
Not efficient if large number of mares need to be bred
How often should she be bred?
Pregnancy rates declined when interval >EOD
No difference between daily and EOD intervals
how long does frozen semen live?
Semen only lives ~ 12 hours
how long does oocyte live?
Oocyte only lives ~6-12 hours
how do we manage breeding with frozen semen? fertility rate?
Semen only lives ~ 12 hours
Oocyte only lives ~6-12 hours
Ovulation induction agent
If only 1 dose is available:
Monitor every 6 hours for ovulation via ultrasound
Breed right on top of ovulation (within 6 hours)
If 2 doses:
Breed prior to anticipated ovulation and again following ovulation
Fertility rate is 50-70% per cycle
Advanced Reproductive Techniques
Embryo Transfer
– Day 7-8 embryo is flushed out of uterus and transferred into a recipient surrogate mare whose cycle has been synchronized – to carry the foal to term and raise it – embryo can also be frozen
ICSI
– Intracytoplasmic Sperm Injection – aspirate follicles from mare’s ovaries to obtain oocytes – fertilized in the lab by injecting a single sperm into oocyte – culture embryos then transfer into a recipient – or freeze them
IVF
– In vitro fertilization – put oocytes and sperm together in a petri dish – fertilize and then culture embryos -
