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A101 Care and Reproductive Management of the Mare

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After breeding the mares for ... Cloning In the laboratory, scientists use somatic cell nuclear transfer techniques to produce animals with genetic material identical ... – PowerPoint PPT presentation

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Title: A101 Care and Reproductive Management of the Mare


1
A101 Care and Reproductive Management of the Mare
2
Reproductive Tract
3
Mare Breeding Characteristics
  • Estrus begins in horses from 15 to 24 months of
    age.
  • Fillies should be 24 to 36 months old before
    breeding.

4
The Reproductive Cycle
  • Mares begin cycling in the spring.
  • Estrus lasts six to eight days in the early
    spring and will shorten to 3 or 4 days by May or
    June.
  • During estrus, follicles develop in the ovaries.
  • The follicles produce the hormone estrogen.
  • Several follicles may develop simultaneously, but
    usually only one follicle will ovulate.

5
Equine Ovaries
6
The Reproductive Cycle
  • When the egg is ready, the follicle will rupture
    releasing the egg. This is called ovulation.
  • Ovulation occurs no more than two days before the
    mare goes out of heat.
  • Occasionally, two follicles will ovulate which
    can produce twins.
  • This is undesirable because twin fetuses have a
    high risk of abortion and cause complications
    during birth.

7
The Reproductive Cycle
  • After ovulation the crater left in the follicle
    will develop what is called a corpus lutetium.
  • The corpus luteum produces the hormone
    progesterone.
  • Progesterone causes the mare to go into diestrus
    (go out of heat).
  • If conception occurs, the corpus luteum will
    continue to produce progesterone and the mare
    will not come into estrus again until after
    parturition.

8
The Reproductive Cycle
9
The Reproductive Cycle
  • The hormone progesterone also helps prepare the
    uterus for the developing fetus.
  • If conception does not occur, prostaglandins are
    released, which causes the corpus luteum to fade
    and the mare will cycle again.

10
Fertilization
  • The ovum leaves the ovaries and enters the
    oviduct.
  • The oviduct is where fertilization takes place.
  • The ovum is viable for 8 to 12 hours, while sperm
    can live for 24 to 48 hours.
  • It takes 4 to 6 hours for the sperm to travel
    through the cervix and oviduct and reach the egg.
  • Due to these time constraints, breeding is
    recommended one to two days prior to ovulation.

11
Fertilization
  • Site of Fertilization
  • Semen is deposited.

12
Fertilization
  • Fertilization occurs when the male gamete (sperm)
    and the female gamete (egg) unite.
  • The DNA located in the head of the spermatogonia
    is then transferred and combined with the DNA of
    the egg forming a zygote.
  • The zygote then travels down the oviduct and
    enters the uterus in about 5- 6 days.
  • In horses, while in the uterus, the embryo is
    very mobile bouncing around between the uterine
    horns until day 16 to 18 where it settles in the
    uterine body and implants itself.

13
Fertilization
  • Embryo Development

14
Gestation
  • From ovulation to parturition the average length
    of gestation is 335 days or a little over 11
    months.

15
Polyestrus
  • Polyestrus means a mare is a seasonal breeder and
    will come into estrus several times per year but
    does not cycle year around.
  • Mares will start cycling irregularly in Jan. and
    Feb. as the days start to get longer.
  • The peak of the estrus cycle occurs in June when
    the days are the longest.
  • Wild horses breed during this time so that foals
    are born during the spring of the year when feed
    is apt to be the best.

16
Polyestrus
  • In Sept. or Oct., as the days shorten, the mare
    ceases to cycle regularly.
  • By late Nov. she stops cycling altogether and
    remains inactive through the winter months.
  • Today the tendency is to mate horses earlier and
    earlier because there is an economic advantage to
    having a larger more developed foal in the sale
    or show ring.
  • This, however, interferes with the mares natural
    timing, and reproductive efficiency is sacrificed
    for economic gain.

17
Polyestrus
  • If early breeding is going to occur, supplemental
    lighting is required.
  • A mare requires about 60 days of artificial
    lighting before ovulation occurs.
  • In order to induce ovulation in early Feb. to
    produce a Jan. 1 foal, artificial lighting must
    be started in late Nov.or early Dec.
  • Sixteen hours of daylight and supplemental light
    and 8 hours of darkness are required.
  • Light can be two 40 watt light bulbs.
  • Hormone supplementation is often also used.

18
Rebreeding
  • At six to twelve days postpartum, most mares will
    come into heat. This is called the foal heat.
  • The conception rate for foal heat is only about
    40 .
  • Mares bred on their foal heat run a greater
    chance of developing uterine infections.
  • The second heat after delivery is the best time
    to breed.

19
Fertility in Mares
  • Each mare in the herd with optimal fertility has
    about a 70 chance of becoming pregnant during
    each cycle she is bred.
  • After breeding the mares for three cycles, about
    96 of the most fertile mares should be bred.
    However, at the end of 3 cycles, if more than 4
    of the mares are still open, the question arises
    as to why some mares repeatedly fail to become
    pregnant.

20
Fertility in Mares
  • There are many factors that can reduce a mares
    chances of becoming pregnant.
  • Some of these factors could include season of the
    year, the mares condition, age, conformation,
    stress, and breeding soundness.

21
Equine Artificial Insemination
  • Equine artificial insemination involves the
    collection of semen from a stallion and the
    deposition of the semen into the mare by
    artificial means.

22
AI Advantages
  • Decreased risk of injury and infection.
  • More mares can be bred to the same stallion.
  • (One ejaculation from a stallion produces nearly
    6 million sperm cells).
  • AI enables horse breeders to purchase genetics
    from superior stallions at a lower price.

23
Equine Artificial Insemination
  • Stallion semen can be frozen. This will allow the
    stallion to continue to produce offspring long
    after he is dead.
  • Compared to fresh semen, frozen semen results in
    lower conception rates in horses.
  • Some breed registries, such as the jockey club
    will not allow AI.
  • Other breed registries will allow AI but not with
    frozen semen. Such is the case with Quarter horse
    Standardbred registries.

24
Equine Artificial Insemination
  • Once collected, fresh semen is measured, and a
    semen extender is added.
  • It is then evaluated for motility, morphology,
    and sperm count.
  • Next it is slowly chilled, and shipped.
  • Fresh semen should be inseminated in the mare in
    less than 36 hours from the time it was taken
    from the stallion.

25
Equine Embryo Transfer
  • Embryo transfer is the process of removing an
    embryo from a mare and placing the embryo in
    another mare. A new embryo can be nonsurgically
    removed from the uterus of a donor mare and
    implanted into a recipient mare.

26
Equine Embryo Transfer Advantages
  • Embryo transfer allows production by older, less
    fertile mares.
  • It also allows increased production from
    genetically superior females.

27
Equine Embryo Transfer Disadvantages
  • It is very expensive and the yield is not very
    high.
  • Embryo transfer is more costly in horses than
    cattle and other animal species due to the
    unavailability of medications to cause a horse to
    super ovulate.

28
Equine Embryo Transfer Phases
  • 1. Synchronization of the donor and the recipient
  • 2. Embryo flushing
  • 3. Embryo transfer procedure

29
Synchronization
  • Synchronization requires the use of the hormones
    progesterone or prostaglandin.
  • Usually two recipients are synchronized for the
    one donor mare.
  • The donor mare is carefully palpated, cultured,
    and bred.
  • The ovulation of both the donor and the
    recipients must be timed to within 12 hours.

30
Embryo Flushing
  • Embryo flushing is performed 7or 8 days after
    insemination.
  • A sterile solution is used to flush the
    microscopic embryo out of the uterus.
  • The embryo is then developmentally sized and
    graded on a scale of 1- 4, 1 being excellent.

31
Embryo Transfer Procedure
  • The embryo is loaded into a uterine transfer
    catheter, mixed with a special nurturing solution
    and is implanted into the uterus of the most
    synchronized recipient.
  • The overall chances per cycle for a successful
    transfer with a young healthy donor are about
    50-60 and 30-40 for older mares.
  • The recipient mare in no way contributes to the
    genetics of the foal.

32
Cloning
  • Cloning has occurred in nature for billions of
    years in plants and some lower animals. Cloning
    is asexually producing offspring that are
    genetically identical to a parent plant or
    animal.
  • For example, a plant grown from a leaf cutting is
    a clone of the original plant because they are
    genetically identical.

33
Cloning
  • In the laboratory, scientists use somatic cell
    nuclear transfer techniques to produce animals
    with genetic material identical to just one
    parent.
  • At present, 10 species have been successfully
    cloned among them cattle, pigs, sheep, mice and
    cats.

34
Cloning
  • Using microsurgery techniques, scientists remove
    the nucleus from an egg cell, which contains the
    cells genetic material, creating an enucleated
    egg.
  • The genetic material from a somatic cell, which
    can be any body cell other than an egg or sperm
    cell, is removed from the cell and injected into
    the enucleated egg.
  • An electric pulse fuses the egg cell and new
    genetic material.
  • The cell is then treated in media that allows it
    to develop into an embryo that can be implanted
    in a surrogate mothers womb and carried to term.

35
Equine Cloning
  • Cloning will not replace sexual reproduction in
    animals, but allows scientists to increase the
    impact of important genetic traits in populations
    of animals and may be the only means of
    reproducing some animals.
  • For example, cells from endangered animals may be
    used to increase populations of some species, but
    cloning them also requires surrogate mothers that
    are genetically similar to carry the embryos to
    term.

36
Equine Cloning
  • The birth of Idaho Gem, the first cloned equine,
    presents other important opportunities.
  • Mules are crosses of horses and donkeys and, like
    most hybrids, are sterile.
  • The only way to produce genetic copies of an
    outstanding mule is through cloning.

37
Equine Cloning
  • Understanding the unique requirements for
    developing cloned equine embryos may also open
    the way to cloning horses with important genetic
    traits.
  • For example, Funny Cide, a winner of the Kentucky
    Derby and Preakness, is a gelding, a genetic
    dead-end unless cloning could produce copies of
    him.

38
1st Equine Clone
  • University of Idaho researchers began trying to
    clone a mule a year after Dolly the sheep was
    cloned in 1997.
  • Out of 307 attempts, there were 21 pregnancies
    and three carried to full term. A mule named
    Idaho Gem was born on May 4, 2003 and was the
    first member of the horse family to be cloned.
    Two other clones were born in June July.
  • The mule clone is the full sibling of a champion
    racing mule owned by Idaho businessman Don
    Jacklin, of Post Falls, Idaho.
  • Donald W. Jacklin paid 400,000 to finance the
    four-year mule cloning project.

39
1st Equine Clone
  • There are differences already evident in the
    mules because the three foals that are
    genetically identical triplets had different
    surrogate mothers.
  • Idaho Gem, the first, was the heaviest at birth,
    weighing 107 pounds. Utah Pioneer, the second,
    was the lightest, weighing 78 pounds. Idaho Star,
    the third born, weighed 87 pounds.

40
1st Equine Clone
  • Both the mothers role and each clones response
    to its environment as the mules grow will provide
    insight into the debate about whether nature or
    nurture rules an animals future.
  • It really does zero in on what is genetically
    controlled and what other factors come into
    play, Vanderwall said.
  • The three clones, all cloned from the same fetal
    mule skin cell line, can only be compared to each
    other. They were not cloned from an adult so
    there is no mature animal with which to compare
    them.
  • The clones future probably will include race
    training as 2-year-olds. Theyre bred to be
    athletes, so one test of their fitness will be
    their athleticism, Woods said.

41
1st Equine Clone
  • A frequent question fielded by the scientists has
    been whether the clones personalities are
    different. Vanderwall said he believes Idaho Gem
    and the youngest clone are the most similar,
    adding, Theyre the most personable, and they
    like to approach people.
  • From that aspect, there does not seem to be a
    direct link to the mares personalities. Idaho
    Dawn, the surrogate mother of the youngest clone,
    is the most wary of the three horses.
  • What can we learn? What can we study about the
    clones? What becomes evident over the life of the
    clones? Vanderwall said those will be the basic
    questions guiding future research.
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