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ASC 410 > Introduction to Equine Reproduction > Flashcards

Introduction to Equine Reproduction Flashcards

1
Q

Mares are seasonally polyestrous and have multiple estrous cycles when?

A

in the spring and summer

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2
Q

Seasonality is triggered by

A

increasing day length

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3
Q

Each estrous cycle is about how long?

A

18-23 days long (average = about 21 days)

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4
Q

What are the two phases of an estrous cycle?

A

estrus and diestrus

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5
Q

Estrus

A

when the mare is receptive to the stallion
-aka heat

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6
Q

What is estrus under the influence of?

A

estradiol

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7
Q

Diestrus

A

when the mare is not receptive to the stallion

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8
Q

What is diestrus under the influence of?

A

progesterone

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9
Q

Anestrous

A

when the mare is not cycling

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10
Q

Each estrus period is usually about..

A

3-7 days long

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11
Q

Each diestrus period is usually about..

A

12-18 days long

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12
Q

Ovulation occurs when?

A

24-48 hours before estrus ends

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13
Q

Fertilization of the oocyte occurs in the…

A

oviduct

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14
Q

The oocyte remains fertile for about

A

12-18 hours after ovulation (window of opportunity once ovulation occurs is small)

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15
Q

Once in the mare, normal sperm should remain fertile for about…

A

48-72 hours if fresh

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16
Q

The best time to breed a mare is…

A

24-48 hours before ovulation

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17
Q

The best time to breed a mare in the estrus cycle is..

A

the second day of estrus and every other day until estrus ends

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18
Q

From day of conception to delivery of a normal foal, gestation length in mares…

A

can range from 10.75-12 months

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19
Q

If a mare conceived on May 15 of 2023, when would you expect her foal?

A

mid/late April 2024

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20
Q

When mares conceive twins, it is considered…

A

normal but not desirable

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21
Q

About how many foals (all breeds) are born each year in the US and Canada?

A

100,000-150,000

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22
Q

If the annual foal crop in 2024 is 150,000 about how many mares were bred in 2023?

A

200,000-225,000 (55-60% live foal rate)

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23
Q

Why is live foal rate important?

A

-the more mares you have to breed to get more foals, the more expensive
-a live foal is needed in order for the stallion owner to get paid
-helps us understand and do better with reproductive efficiency

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24
Q

Broodmare

A

any mare intended for breeding

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25
Q

Barren mare

A

mare was bred and didn’t get pregnant

26
Q

Maiden mare

A

a mare being bred or producing a foal for the first time

27
Q

Rested mare

A

mare has had foals but is not bred or pregnant one year

28
Q

Wet mare

A

mare that is lactating

29
Q

A “breeding system”

A

the management process intended to result in a foal

30
Q

What is the breeding system regulated by?

A

breed associations
-some systems/procedures may be completely prohibited
-some systems/procedures may be allowed under some circumstances -

31
Q

Two main types of breeding systems:

A

-assisted reproduction (AI, embryo transfer, etc.)
-natural service

32
Q

Assisted reproduction systems have…

A

-large human intervention
-breed/registry may include restrictions, require fees and permits

33
Q

Artificial insemination

A

semen is collected from a stallion and later inseminated in a mare

34
Q

Types of semen:

A

-fresh
-cooled
-frozen

35
Q

Fresh semen

A

used in a few hours, usually on farm or local

36
Q

Cooled semen

A

5 degrees C
-shipped overnight
-most common in the US

37
Q

Frozen semen

A

frozen in liquid N
-stored frozen
-shipped frozen
-can have it for years
-some stallions’ semen does not tolerate being frozen

38
Q

Typical stallion management for AI:

A

-train stallion to use phantom/dummy
-train stallion to use artificial vagina
-collect semen as needed

39
Q

What is a common collection schedule for AI for stallions?

A

-3-4 times/week: M, W, F, maybe Sat
-if freezing, when the stallion is available

40
Q

What do people typically do with the first stallion collection?

A

test collect to determine best conditions, temp, extenders, freezability, etc.

41
Q

When collecting semen to breed mares:

A

-evaluate semen: volume, concentration, motility, morphology
-extend and divide doses
-cool and ship or freeze and store/ship

42
Q

Typical mare management for AI

A

-heat detection program (teasing, vet exams, etc.) to forecast ovulation time
-order semen
-schedule for vet insemination
-check mare for ovulation (vet) in 24 hours

43
Q

When do we want to inseminate AI for a mare?

A

close to ovulation

44
Q

Embryo transfer

A

A donor mare is bred (usually AI) and ovulation is tracked. The embryo is collected and inserted into a recipient mare that will carry the foal to term

45
Q

When is the donor mare flushed for the embryo?

A

about day 7

46
Q

Who is the official dam of the foal from embryo transfer?

A

the donor mare

47
Q

Recipient mare in embryo transfer:

A

-synchronized with donor, ideally ovulate at the same time
-embryo is transferred after collection

48
Q

Success with fertile mares in embryo transfer is as high as

A

85%

49
Q

How to choose a recipient mare for ET:

A

-reproductively healthy
-raised a previous foal (good maternal behavior)
-same size as donor

50
Q

Natural service is allowed by…

A

all breed registries
-it is the only one allowed in the Thoroughbred industry

51
Q

Natural service is also known as:

A

live cover

52
Q

Hand-mating live cover

A

-mares travel to where the stallion is
-mares wear a neck cover/tail wraps/boots to protect the stallion and her during breeding
-mare is teased and an ultrasound is done to check estus cycle
-mare and stallion are being held and possibly assisted while mating occurs

53
Q

Pasture mating

A

stallion breeds mare(s) in an enclosure
-a mare may be taken to a stallion and turned out with him for a certain period of time
-more commonly a stallion is put in with a herd of mares at the beginning of the breeding season and left there until the breeding season is over

54
Q

Advantages of pasture mating

A

-less stressful
-less work for people
-no risk of injury to people
-effective (allowed by registries)
-allows “extensive” management system
-lower cost (labor/equiptment)

55
Q

Disadvantages of pasture mating

A

-more risk of infection transmittal
-more risk of injury to all horses involved (including foals)
-no info on conception rate until end of season
-less info on breeding dates (then won’t know foaling date)
-fewer mares per stallion
-reduce genetic choices

56
Q

Advantages of hand mating

A

-known breeding date
-genetic choices
-better hygiene
-less risk of injury to the horses (especially foals)
-ability to follow pregnancy rates
-allowed by all registries
-collect semen for evaluation
-more mares per stallion (with high management)

57
Q

Disadvantages of hand mating

A

-more labor before and during breeding
-more stressful for mare (may need to travel, or leave foal)
-more risk for people
-higher cost (more labor and facilities)

58
Q

Advantages of AI

A

-use of competition horses
-more mares/season
-more mares/ejaculate (less stressful for stallion)
-more genetic choice
-mare and stallion in different places (better biosecurity)
-less risk of injury for people and horses
-more opportunities to evaluate semen

59
Q

Disadvantages of AI

A

-cost (shipping, vet procedures, equipment, access to more expensive stallions)
-genetics (could decrease genetic diversity if too many mares are bred to one or two stallions)
-scheduling and logistics are challenging
-more expertise needed
-registry requirements (fees or not allowed at all)

60
Q

Advantages of embryo transfer

A

-preserve genetics of mares that are not capable of having a foal
-obtain foals from mares that are currently competing
-may be able to obtain several foals from 1 mare/year

61
Q

Disadvantages of embryo transfer

A

-expertise and equipment needed
-expense (at least two mares)
-registration and reporting requirements

ASC 410 (22 decks)

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