Equine Breeding Programs

Question 1

What is a stallions book?

Answer 1

list of mares that will be bred to him in a given year

Question 2

What is a cover

Answer 2

when a stallion breeds a mare naturally

Question 3

what is a mount/phantom/dummy

Answer 3

fake mare that allows us to collect semen for AI when stallion mounts it

Question 4

what is an artificial vagina

Answer 4

what we use to collect semen from a stallion

Question 5

what are the four methods of mare breeding

Answer 5

-natural service
-on farm AI
-shipped fresh chilled AI
-frozen semen AI

Question 6

what is the only approved method of breeding in thoroughbreds to obtain a registered foal?

Answer 6

Natural cover

Question 7

advantages of natural cover breedings (5)

Answer 7

-Minimal equipment expenses (no lab etc)
-Obvious when mare is in heat
-No knowledge of semen handling required
-No semen shipments lost
-High conception rate

Question 8

disadvantages of natural cover breedings (4)

Answer 8

-Risks of injury to horses and handlers
-One mare bred per ejaculation
-Mares must travel to stallion (often with new foal)
~assoc. risks and costs
-Some mares will not accept a stallion even when in estrus

Question 9

What needs to be done in natural cover programs to assure no disease transmission occurs?

Answer 9

-Pre-breeding culture swabs
-Clean breeding practices

Question 10

advantages of AI (5)

Answer 10

-Mare & foal stay at home
-Efficient
-Many mares can be bred with a single collection
-Fresh-chilled semen lasts about 48+ hours when diluted with semen extender
-Frozen semen - stallion continues performance career without interruption

Question 11

disadvantages of AI (2)

Answer 11

-Increased expenses
◦ Laboratory costs
◦ Semen shipping cost
◦ Veterinary costs of mare management

-Considerable knowledge in semen handling

Question 12

advantages of frozen semen (4)

Answer 12

-Permanent storage
-Semen available anytime
-Stallions continue performing
-Improved genetics – use of stallions around the world

Question 13

disadvantages of frozen semen (1)

Answer 13

-Higher costs
◦ Semen collection, freezing, storage, transport
◦ Very intensive mare monitoring required
◦ Requires specialized equipment and expertise

Question 14

characteristics of anovulatory season (dec-feb)

Answer 14

◦ Variable behavior
~Usually uninterested in stallion – “meh”
◦ Small ovaries, small follicles <10 mm
◦ Flaccid uterus, no edema
◦ Cervix – pale, tight or relaxed

Question 15

levels of GnRH, FSH, LH, estrogen and P4 in winter anestrus

Answer 15

-decreased GnRH and FSH
-no LH, estrogen or P4

Question 16

What environmental factor triggers the resurgence of ovarian activity?

Answer 16

Increased daylength

Question 17

What hormone is released in response to increased daylength?

Answer 17

GnRH

Question 18

What happens to FSH levels during the resurgence of ovarian activity?

Answer 18

it increases

Question 19

What is notable about the follicles during spring transition?

Answer 19

Follicles start to grow but do not produce much estrogen

Question 20

What is the status of LH during the resurgence of ovarian activity in spring transition?

Answer 20

There is low bioactive LH and no LH receptors, so ovulation does not occur

Question 21

Describe the characteristics of the ovaries during the spring transition

Answer 21

The ovaries are large with multiple follicles

Question 22

What changes occur in the uterus during spring transition?

Answer 22

The uterus is flaccid with variable edema

Question 23

What is the typical state of the cervix during the resurgence of ovarian activity?

Answer 23

The cervix is usually relaxed and may appear pale to pink

Question 24

when does ovulatory season occur

Answer 24

may to september

Question 25

what signals the ovulatory season

Answer 25

the first ovulation of the year..... cyling then occurs every 21d after that

Question 26

What are some characteristics of estrus (behaviour and what we see on ultrasound)

Answer 26

-Teasing – signs of estrus – receptive, winking of vulva, posturing, urination -Follicles growing on ovaries -Flaccid uterus, open, pink cervix on floor of vagina -Uterine edema

Question 27

what are the characteristics of diestrus (behaviour and ultrasound)

Answer 27

-Teasing – aggressively refuses stallion ◦ Kicks, bites, pins ears, squeals -Corpus luteum on ovary– high progesterone -Toned uterus -No edema

Question 28

what hormone is very high during diestrus

Answer 28

progesterone

Question 29

when does the fall transition occur and why

Answer 29

october to november due to decreasing daylength

Question 30

what are autumn follicles

Answer 30

they are anovulatory follicles... or failed ovulations

Question 31

what happens to LH and GnRH in the mare during the fall transition

Answer 31

decreased LH production (gene turns off) decreased GnRH

Question 32

what happens to the ovary during fall transition

Answer 32

decreased P4 levels, luteal failure, shortened luteal phase

Question 33

what are some reasons to manipulate a mares cycle? (5)

Answer 33

-Out of season breeding -Synchronize a group of mares for breeding -Control timing of estrus (eg. For shipping semen) -Induce ovulation (eg. Once semen arrives) -Control unwanted estrous behavior (performance mares)

Question 34

how do you implement standard method for photoperiod manipulation in mares?

Answer 34

-14.5 - 16 hours of light total -Add light to end of day

Question 35

what is the idea behind the standard method for photoperiod manipulation in mares?

Answer 35

-Idea is to stimulate earlier spring transition period -Resume cycling 60-70 days after starting -Start between Nov 15 – Dec 5 for Feb breeding -Continue until days are 14 hrs long

Question 36

what is the pulse lighting method of photoperiod manipulation in mares?

Answer 36

-Photosensitive period 8–10 hours after onset of darkness -Usually 2 am – 4 am -1.5-2 hours of “lights on” -Must be high intensity light (100 Watt) -Start between Nov 15-Dec 5 and continue until days are 14 hrs -Saves energy!

Question 37

Why won't PGF2α be effective in treating anestrus mares?

Answer 37

PGF2α is ineffective because there are no active CL (corpora lutea) to regress, as anestrus mares lack sufficient ovarian activity.

Question 38

Why won't GnRH or hCG work in anestrus mares?

Answer 38

GnRH or hCG are ineffective because there is insufficient ovarian responsiveness and low levels of LH receptors, leading to no ovulation

Question 39

What are dopamine antagonists used in treating anestrus mares?

Answer 39

Sulpiride or domperidone.

Question 40

How do dopamine antagonists affect prolactin levels?

Answer 40

They increase prolactin levels, which can enhance follicular activity.

Question 41

Are dopamine antagonists effective on their own for treating anestrus mares?

Answer 41

No, they are not very effective on their own and may need to be used in conjunction with other treatments

Question 42

what is the frustrating part of spring transition for vets?

Answer 42

there is growth of dominant sized follicles that just fail to ovulate

Question 43

what is used to induce first ovulation of the year

Answer 43

P4 combination of domperidone and estrogen GnRH or hCG

Question 44

What is the purpose of P4 therapy in mares

Answer 44

Mimics a functional CL – inhibits LH release; little effect on FSH

Question 45

Progesterone therapy; requirements

Answer 45

-Regumate = Synthetic progestin (Altrenogest) -Give orally for 10-14 days -Must have follicles >25 mm (mid transition) -Give PGF2a on last day (just in case she ovulated during treatment)

Question 46

Process for combination therapy in transitional mares

Answer 46

-One Initial 75 mg Estradiol Cypionate (ECP) injection I.M. and 500 mg domperidone orally daily for 7 - 14 days (addition of estrogen enhances LH receptors on the growing follicles)

Question 47

are CIDRs used in north america? why?

Answer 47

No, results in nasty vaginitis

Question 48

what is the most common way of prolonging the luteal phase

Answer 48

oral altrenogest (regumate)

Question 49

why is hCG used in mares?

Answer 49

to induce ovulation

Question 50

when do you give hCG to the mare?

Answer 50

Give to a mare in estrus with: -Follicle > 35 mm and Strong uterine edema

Question 51

when will a mare ovulate after you give hCG

Answer 51

-Most will ovulate within 48 hours -Most at 36 hours after administration (85.1% by then)

Question 52

what drug do you switch to if you have used hCG multiple times per breeding season?

Answer 52

gNRH

Question 53

what is the age effect of hCG

Answer 53

repeated exposures = less effective

Question 54

what is the effectiveness of GnRH

Answer 54

Over 95% of mares ovulate within 48 hours after injection when given in estrus with dominant follicle > 33 mm

Question 55

is there any concern of reduced efficacy over time for GnRH

Answer 55

no

Question 56

what happens to the follicles as ovulation approaches

Answer 56

softer, irregular in shape, larger

Question 57

how much does a follicle grow per day on average

Answer 57

3-6mm per day

Question 58

details about combination programs (P and E) for mares

Answer 58

-Combines daily progesterone and estradiol injections -Estradiol suppresses FSH – control of follicle waves -10 day treatment -PGF2a on last day -In estrus 7-9 days after last injections -Predictable ovulation day 20-21 of program

Question 59

what does the size of the follicle at ovulation depend on?

Answer 59

breed and mare history