equine breeding management

Question 1

How long does semen live for?

Answer 1

Depends on the stallion and handling, but on average:
Fresh = 2-5 days – very stallion dependent
Cooled-shipped = 48 hours
Frozen = ~12 hours

Question 2

How long do oocytes live after ovulation?

Answer 2

6-12 hours

Question 3

methods to determine where a mare is at in her cycle

Answer 3

Records
Teasing
Vaginoscopy
 Palpation
 Ultrasound

Question 4

how will mare behave for teaser in diestrus?

Answer 4

Mare is NOT receptive
 Squeals
Kicks out
Pins her ears

Question 5

how will uterus feel during diestrus?

Answer 5

you feel uterine tone

Question 6

what will we see on ultrasound during diestrus

Answer 6

-no uterine edema
-follicles

Question 7

what will you see on vaginoscopy and palpation during diestrus (looking at cervix)

Answer 7

Looks pale (“white”)
Located in central vagina

On vaginal palpation you feel:
 Pencil-like structure
 Tight

Question 8

what should we do to induce estrus?

Answer 8

Manipulate the luteal phase

Question 9

How can we shorten the luteal phase?

Answer 9

 Prostaglandin injection
> causes luteolysis

Question 10

prostaglandin injection side effects

Answer 10

Sweating, colicky, diarrhea

Question 11

how long after prostaglandin injection should we see heat

Answer 11

Should come into heat in 2-5 days

Question 12

more behaviour during estrus when teased

Answer 12

 Urinating
 Winking
Lifting her tail off to the side
Squatting

Question 13

how does uterus feel during estrus

Answer 13

Uterus feels flaccid

Question 14

what do we see on ultrasound during estrus

Answer 14

Uterine edema (grade 1-2)
-no CL
-follicle

Question 15

what will we see on vaginoscopy during estrus

Answer 15

Soft, relaxed cervix, edematous

Question 16

how fast does a follicle grow during a mare’s heat? what other changes?

Answer 16

Grows approx. 3mm/day
Becomes Softer
More irregular shape
Bright border

Question 17

Follicle size at Ovulation

Answer 17

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 +

Question 18

When to order semen?

Answer 18

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

Question 19

when is it acceptable to induce ovulation?

Answer 19

when follicle is large enough diameter
Good uterine edema

Question 20

how do we induce ovulation? how long after will it occur?

Answer 20

 hCG (human chorionic gonadotropin)
>Acts like LH

 Deslorelin acetate
>GnRH analogue

Should ovulate within 48hrs

Question 21

what is a breeding dose of sper?

Answer 21

A breeding dose is 500x106 progressively motile sperm

Question 22

waht should sperm concentration be when we cool it for shipping

Answer 22

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)

Question 23

what is semen extender? what does it do?

Answer 23

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

Question 24

Preparation of sperm for cooling & shipping

Answer 24

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

Question 25

how do you perform AI?

Answer 25

 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

Question 26

what do we do after AI?

Answer 26

Ovulation Check

Question 27

how do we do an ovulation check after AI? outcomes?

Answer 27

-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

Question 28

mare pregnancy rates with AI?

Answer 28

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

Question 29

how do we diagnose pregnancy in the mare?

Answer 29

Pregnancy Diagnosis
14 day pregnancy ultrasound
26 day pregnancy ultrasound – heart beat check
45 day
60 day
Autumn check

Question 30

Live cover without palpation/ultrasound; how do we manage?

Answer 30

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

Question 31

How often should she be bred?

Answer 31

Pregnancy rates declined when interval >EOD

No difference between daily and EOD intervals

Question 32

how long does frozen semen live?

Answer 32

Semen only lives ~ 12 hours

Question 33

how long does oocyte live?

Answer 33

Oocyte only lives ~6-12 hours

Question 34

how do we manage breeding with frozen semen? fertility rate?

Answer 34

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

Question 35

Advanced Reproductive Techniques

Answer 35

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 -