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Theriogenology > Equine Breeding Programs > Flashcards

Equine Breeding Programs Flashcards

1
Q

What is a stallions book?

A

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

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2
Q

What is a cover

A

when a stallion breeds a mare naturally

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3
Q

what is a mount/phantom/dummy

A

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

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4
Q

what is an artificial vagina

A

what we use to collect semen from a stallion

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5
Q

what are the four methods of mare breeding

A

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

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6
Q

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

A

Natural cover

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7
Q

advantages of natural cover breedings (5)

A

-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

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8
Q

disadvantages of natural cover breedings (4)

A

-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

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9
Q

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

A

-Pre-breeding culture swabs
-Clean breeding practices

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10
Q

advantages of AI (5)

A

-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

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11
Q

disadvantages of AI (2)

A

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

-Considerable knowledge in semen handling

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12
Q

advantages of frozen semen (4)

A

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

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13
Q

disadvantages of frozen semen (1)

A

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

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14
Q

characteristics of anovulatory season (dec-feb)

A

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

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15
Q

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

A

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

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16
Q

What environmental factor triggers the resurgence of ovarian activity?

A

Increased daylength

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17
Q

What hormone is released in response to increased daylength?

A

GnRH

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18
Q

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

A

it increases

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19
Q

What is notable about the follicles during spring transition?

A

Follicles start to grow but do not produce much estrogen

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20
Q

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

A

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

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21
Q

Describe the characteristics of the ovaries during the spring transition

A

The ovaries are large with multiple follicles

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22
Q

What changes occur in the uterus during spring transition?

A

The uterus is flaccid with variable edema

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23
Q

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

A

The cervix is usually relaxed and may appear pale to pink

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24
Q

when does ovulatory season occur

A

may to september

25
Q

what signals the ovulatory season

A

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

26
Q

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

A

-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

27
Q

what are the characteristics of diestrus (behaviour and ultrasound)

A

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

28
Q

what hormone is very high during diestrus

A

progesterone

29
Q

when does the fall transition occur and why

A

october to november

due to decreasing daylength

30
Q

what are autumn follicles

A

they are anovulatory follicles… or failed ovulations

31
Q

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

A

decreased LH production (gene turns off)

decreased GnRH

32
Q

what happens to the ovary during fall transition

A

decreased P4 levels, luteal failure, shortened luteal phase

33
Q

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

A

-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)

34
Q

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

A

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

35
Q

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

A

-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

36
Q

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

A

-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!

37
Q

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

A

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

38
Q

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

A

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

39
Q

What are dopamine antagonists used in treating anestrus mares?

A

Sulpiride or domperidone.

40
Q

How do dopamine antagonists affect prolactin levels?

A

They increase prolactin levels, which can enhance follicular activity.

41
Q

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

A

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

42
Q

what is the frustrating part of spring transition for vets?

A

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

43
Q

what is used to induce first ovulation of the year

A

P4
combination of domperidone and estrogen
GnRH or hCG

44
Q

What is the purpose of P4 therapy in mares

A

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

45
Q

Progesterone therapy; requirements

A

-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)

46
Q

Process for combination therapy in transitional mares

A

-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)

47
Q

are CIDRs used in north america? why?

A

No, results in nasty vaginitis

48
Q

what is the most common way of prolonging the luteal phase

A

oral altrenogest (regumate)

49
Q

why is hCG used in mares?

A

to induce ovulation

50
Q

when do you give hCG to the mare?

A

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

51
Q

when will a mare ovulate after you give hCG

A

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

52
Q

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

A

gNRH

53
Q

what is the age effect of hCG

A

repeated exposures = less effective

54
Q

what is the effectiveness of GnRH

A

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

55
Q

is there any concern of reduced efficacy over time for GnRH

A

no

56
Q

what happens to the follicles as ovulation approaches

A

softer, irregular in shape, larger

57
Q

how much does a follicle grow per day on average

A

3-6mm per day

58
Q

details about combination programs (P and E) for mares

A

-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

59
Q

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

A

breed and mare history

Theriogenology (25 decks)

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