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Advanced Reproduction Physiology (Part 3)

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Title: Advanced Reproduction Physiology (Part 3)


1
Advanced Reproduction Physiology (Part 3)
  • Isfahan University of Technology
  • College of Agriculture, Department of Animal
    Science

Prepared by A. Riasi http//riasi.iut.ac.ir
2
Physiology of Pregnancy and Embryo Development
3
Spermatozoa in female tract
  • In natural mating semen are introduced in
  • Vagina
  • Cervix
  • Within the female tract spermatozoa are lost by
  • Phagocytosis by neutrophils
  • Physical barrier including the cervix

4
Spermatozoa in female tract
  • Two stages for spermatozoa transport
  • Rapid transport
  • Oxytocin secretion
  • Prostaglandins
  • Sustained transport

5
Spermatozoa in female tract
  • Factors may affect spermatozoa transport in
    cervix
  • Sperm motility
  • Physicochemical change in cervix secretions

6
Spermatozoa in female tract
7
Spermatozoa in female tract
  • Sperm capacitation
  • Chemical changes
  • Remove decapacitation factors
  • Remove cholesterol
  • Membrane ions changes
  • Physical and morphological changes

8
Spermatozoa in female tract
  • Higher levels of FPP prevent capacitation
  • FPP is found in the seminal fluid and comes into
    contact with the spermatozoa upon ejaculation.
  • It has a synergistic stimulatory effect with
    adenosine that increases adenylyl cyclase
    activity in the sperm.

9
Spermatozoa in female tract
  • Other chemical changes
  • Removal of cholestrol and non-covalently bound
    epididymal/seminal glycoproteins is important.
  • The result is an increased permeability of sperm
    to Ca2, HCO3- and K
  • An influx of Ca2 produces increased
    intracellular cAMP levels.

10
Spermatozoa in female tract
  • Altering the lipid composition of sperm plasma
    membranes affects
  • The ability of sperm to capacitate
  • Acrosomal reaction
  • Respond to cryopreservation.

11
Spermatozoa in female tract
  • High intracellular concentrations of Ca2, HCO3-
    and K are required for
  • Acrosome reaction
  • Fuse with the oocyte.

12
Spermatozoa in female tract
  • Physical and morphological changes

13
The oocyte moving in female tract
  • Oocyte is transported by cilia of oviduct.
  • Smooth muscles of oviduct adjust the time of
    oocyte transportation.
  • The mature egg can only survive for about 6
    hours, so the time of insemination is important.

14
Sperm penetration
  • A series of events
  • First step acrosome reaction
  • After the reaction, the vesicles are sloughed,
    leaving the inner acrosomal membrane and the
    equatorial segment intact.

15
Sperm penetration
  • A spermatozoon has to penetrate four layers
    before it fertilizes the oocyte

16
Sperm penetration
17
Sperm penetration
18
Sperm penetration
19
Sperm penetration
20
Sperm penetration
  • Three changes occur in the oocyte after
    penetration of vitelline membrane

21
Fertilization
  • Fertilization has two important genetic
    consequences
  • The diploid chromosome number is restored (2n).
  • The genetic sex of the zygote is determined

22
Fertilization
23
Cleavage
24
Cleavage
25
Cleavage
26
Increase conception rate
  • Embryonic mortality in the initial seven days of
    gestation
  • Fertilization failure
  • Genetic defects
  • Impaired embryonic development

27
Increase conception rate
  • Measuring embryonic mortality in weeks two and
    three of gestation is much more challenging.
  • This period coincides with the maternal
    recognition of pregnancy.

28
Increase conception rate
  • Successful establishment of pregnancy depends on
    a delicate balance between
  • Luteolytic mechanisms inherent to the endometrium
    at the end of diestrus.
  • Antiluteolytic mechanisms, orchestrated by the
    conceptus.

29
Increase conception rate
  • Some strategies for increasing conception rate
  • Using TAI protocols
  • Stimulate growth and/or differentiation of the
    pre-ovulatory follicle
  • Stimulate CL growth rate
  • Increase plasma progesterone concentrations in
    the initial three weeks after insemination.

30
Increase conception rate
  • Decrease the effects of a dominant follicle
    during the critical period
  • Antiluteolytic stimulus provided by the conceptus
  • Decrease uterine luteolytic capacity

31
Increase conception rate
  • Reproductive physiologists had long searched to
    develop a synchronization program.
  • Ovsynch synchronizes AI at a fixed-time without
    the need for estrus detection.

32
Increase conception rate
  • Some factors may affect Ovsynch results
  • The stage of the estrous cycle
  • Cyclic status at the time that GnRH is
    administered (Bisinotto et al., 2010)

33
Increase conception rate
  • Researchers have modifed the original Ovsynch
    protocol to try to
  • Improve synchrony and fertility through
    presynchronization
  • Altering the timing of AI in relation to
    ovulation
  • Testing the various injection intervals of the
    original protocol

34
Increase conception rate
  • TAI programs need day-to-day operation, so it may
    use for
  • Lactating dairy cows with little or no estrus
    detection at all
  • Voluntary Waiting Period (VWP)

35
Increase conception rate
  • Factors explaining the variation in conception
    rate to TAI among herds may include
  • The proportion of anovular cows
  • The follicular dynamics of individual cows
  • The ability of farm personnel to implement
    Ovsynch

36
Increase conception rate
  • Following this first report, numerous protocols
    have been proposed and routinely applied in high
    production dairy cows (Wiltbank et al., 2011).

37
Increase conception rate
  • Programming cows for first postpartum AI using
    presynch/ovsynch
  • Use of presynch for programming lactating dairy
    cows to receive their first postpartum TAI can
    improve first service conception rate in a dairy
    herd.

38
Increase conception rate
One possible hormone injection and TAI schedule
for the Presynch/Ovsynch protocol based on the
results of Moreira et al., 2000
39
Increase conception rate
  • In an assay, cycling cows conception rate was
    29 for Ovsynch and 43 for Presynch.
  • These protocols may presents low efficiency when
    applied in tropical condition.

40
Increase conception rate
  • Estradiol plus progesterone based protocol
  • Exogenous P4 and progestins has consequences
  • Suppresses LH release
  • Alters ovarian function
  • Suppresses estrus
  • Prevents ovulation

41
Increase conception rate
  • Novel studies introduced the use of E2 plus P4 to
    control follicular wave dynamics (Sá Filho et
    al., 2011)
  • Several studies found that E2 plus P4 treatment
    suppress the growing phase of the dominant
    follicle.
  • The interval from E2 treatment to follicular wave
    emergence seemed to depend on FSH resurgence
    (O'Rourke et al., 2000).

42
Increase conception rate
  • In E2 plus P4 protocols, a lower dose of E2 is
    normally given from 0 to 24 h after progestin
    removal to induce a synchronous LH surge (Hanlon
    et al., 1997 Lammoglia et al., 1998 Martínez et
    al., 2005 Sales et al., 2012).

43
Increase conception rate
  • Anestrous cows have insufficient pulsatile
    release of LH to support the final stages of
    ovarian follicular development and ovulation.
  • What we should do for anestrous cows?
  • The treatment with equine chorionic gonadotropin
    (eCG) may be effective.

44
Increase conception rate
  • eCG administration for anestrous or low BCS dairy
    cows has benefit effects (Souza et al., 2009
    Garcia-Ispierto et al., 2011).

45
Increase conception rate
  • Antiluteolytic strategies
  • Pharmacological
  • Mechanical
  • Nutritional
  • Management

46
Increase conception rate
  • Strategies to increase progesterone
  • Daily injection of progesterone
  • Using of progesterone releasing intravaginal
    device (PRID)
  • Inducing the formation of accessory corpora lutea
    by the ovulation of the first wave dominant
    follicle.

47
Increase conception rate
  • Effect of estrogen
  • Inskeep (2004) indicated that estrogen secretion
    from a large follicle from days 14 to 17 of
    pregnancy may negatively affect embryo survival.
  • This hormone has a central role in PGF production
    and luteolysis.

48
Increase conception rate
  • Some strategies for reducing estrogent
  • Absence of dominant follicles
  • Reduction of their steroidogenic capacity
  • Reduction of endometrial responsiveness to
    estradiol during the period of maternal
    recognition of pregnancy
  • Pharmacological approaches

49
Increase conception rate
  • Pharmacological strategies
  • The GnRH-hCG treatment
  • It induced an increase in plasma progesterone
    concentrations

50
Increase conception rate
  • Antiluteolytic strategies
  • Antiinflamatory drugs
  • Fat feeding
  • Bovine somatotropin (bST)

51
Increase conception rate
  • Synthesis of PGF results from a coordinated
    cascade of intracellular events.
  • A rate limiting step in this cascade is the
    conversion of arachidonic acid to
    prostaglandin-H2 (PGH).

52
Increase conception rate
  • The key enzyme is PTGS2 or COX-2.
  • The PGH is subsequently converted to PGF.
  • Guzeloglu et al. (2007) treated Holstein heifers
    with flunixin meglumine, a non-steroidal
    antiinflamatory drug which inhibits PTGS2
    activity, on days 15 and 16 after insemination.

53
Increase conception rate
  • Fat feeding influences several aspects of
    reproduction in cattle
  • (See review by Santos et al., 2008).

54
Increase conception rate
  • Feeding long chain fatty acids can modulate PGF
    production in the endometrium.
  • Effect of n-3 fatty acids (Mattos et al., 2003,
    2004)
  • Effect of N-6 fatty acids (Pettit and
    Twagiramungu, 2004)
  • A summary of the effects of fatty acid feeding on
    cattle fertility reported by Santos et al. (2008).

55
Increase conception rate
  • Strategies for growth of the conceptus
  • Secretion of IFN is positively associated with
    conceptus size.
  • Administration of bST.

56
Maternal recognition of pregnancy
  • Mother quickly becomes cognizant of the
    cleavage-stage embryo within her body.
  • Mother reacts to embryo presence, but its not
    enough for the pregnancy to proceed.

57
Maternal recognition of pregnancy
  • For maternal recognition it is necessary
  • The normal cyclic regression of CL be prevented
    in order to maintain progesterone production.
  • The conceptus has also to ensure that an adequate
    supply of maternal blood reaches the sites of
    placentation.

58
Maternal recognition of pregnancy
  • The conceptus is recognized as foreign by the
    mother and it must nevertheless take steps to
    avoid a losing confrontation with the maternal
    immune system.
  • The conceptus does not become vascularized by the
    host's blood supply.

59
Maternal recognition of pregnancy
  • The ways in which different species
  • In human
  • Luteolysis is initiated by an intraovarian
    mechanism, although many believe it requires
    local production of PGF2a.

60
Maternal recognition of pregnancy
  • Luteolysis in these species is avoided by the
    intervention of chorionic gonadotrophin (CG)
  • The CG probably binds to LH receptors
  • The CG can stimulates progesterone production
  • The CG exerts a protective action against PGF2a

61
  • In rodents
  • Rodent do not produce a CG at all.
  • During pseudopregnancy in the rat, the cycle is
    lengthened to 12 days before the CL regress.
  • This extension of CL life span is the result of
    surges of pituitary prolactin release.
  • If the rat is pregnant, a series of placental
    lactogens and prolactin-like hormones produced by
    the placenta.

Maternal recognition of pregnancy
62
  • In pigs
  • Estrogen released by the trophoblast as it begins
    to elongate is probably the initial signal to the
    mother that she is pregnant.

Maternal recognition of pregnancy
63
  • In horses
  • The equine conceptus forms an encapsulated
    spherical structure between days 12 and 14.
  • The constant patrolling may be the key to the
    mechanism that inhibits PGF2a release.

Maternal recognition of pregnancy
64
  • In cattle and sheep
  • The conceptus begins to intervene in the
    luteolytic process three to four days before the
    CL actually become dysfunctional.
  • In these species, the antiluteolytic substance,
    an unusual Type I interferon (IFN)-t, has been
    reviewed on numerous occasions in the literature.
  • Its presence in the lumen clearly suppresses the
    normal pattern of pulsatile release of PGF2a.

Maternal recognition of pregnancy
65
Maternal recognition of pregnancy
  • Importance of progesterone
  • The concentrations of progesterone at a critical
    time before implantation is important for cows
    pregnancy.
  • Two logical possibilities for lower progesterone
    in the lactating dairy cows
  • Secretion by the corpus luteum is reduced
  • Metabolism of progesterone is increase

66
Maternal recognition of pregnancy
  • Importance of progesterone
  • Some factors may affect the metabolism and
    excretion of progesterone
  • Feed intake
  • Milk yield
  • Administration of exogenous progesterone

67
Embryonic loss
  • Much prenatal mortality occurs in all mammals.
  • Higher amount of embryonic wastage occurs
    following IVF and ET.
  • The majority of these losses occur prior to or
    during implantation.

68
Embryonic loss
  • Embryonic losses in sheep and cattle
  • It most occurring in the first 3 wk of pregnancy.
  • Natural asynchronies
  • The late onset of the first meiotic division may
    lead to some oocytes being delayed in their
    maturation.
  • A second natural cause of asynchrony may be due
    to delayed fertilization.
  • Finally, embryos are known to cleave at different
    rates.

69
Embryonic loss
  • Injection interferons have ability to improve
    pregnancy success in ewes may be due
  • The rescue of embryos delayed.

70
Embryonic loss
  • Pig conceptuses attain control over maternal
    progesterone production
  • Releasing estrogen and probably other factors
    just prior to the time the CL would normally
    regress.
  • The second consequence is that it induces the
    massive release of uterine secretions from the
    uterine glandular and surface epithelium

71
Pregnancy-Associated Glycoproteins (PAG)
  • In 1982 the partial purification and
    characterization of a pregnancy-specific protein
    (PSP-B) was reported from cattle.
  • More recently, isolated several isoforms of PAG
    from bovine placental tissue.

72
Pregnancy-Associated Glycoproteins (PAG)
  • It is now clear that PSP-B and PAG-1 are
    identical in sequence.
  • The presence of PAG-1 (or PSP-B) in blood serum
    has provided the basis of a potentially useful
    pregnancy test in cattle.

73
Pregnancy-Associated Glycoproteins (PAG)
  • The antigen generally becomes detectable by about
    day 20 postbreeding.
  • In cattle, concentrations of the antigen rise
    gradually during gestation and peak just prior to
    parturition.

74
Pregnancy-Associated Glycoproteins (PAG)
  • The PAG have a well-defined peptide- binding
    cleft.
  • They are relatively hydrophobic polypeptides.
  • They are unlikely to have enzymatic activity.

75
Pregnancy-Associated Glycoproteins (PAG)
  • Two possible functions for PAG are suggested
  • They could be hormones, which, by virtue of their
    binding clefts, are able to bind specific cell
    surface receptors on maternal target cells.
  • The second suggestion is that PAG sequestered or
    transported peptides

76
Some research papers associated to this lecture
1-Pancarci, et al. 2002. Use of estradiol
cypionate in a presynchronized timed artificial
insemination program for lactating dairy cattle.
J. Dairy Sci. 85122131. 2- Franco, et al.
2006. Effectiveness of administration of
gonadotropin-releasing hormone at Days 11, 14 or
15 after anticipated ovulation for increasing
fertility of lactating dairy cows and
non-lactating heifers. Theriogenology 66
945954. 3- De Rensis, et al. 2008. Inducing
ovulation with hCG improves the fertility of
dairy cows during the warm season. Theriogenology
69 10771082 4- Bartolome, et al. 2005.
Strategic use of gonadotrophin-releasing hormone
(GnRH) to increase pregnancy rate and reduce
pregnancy loss in lactating dairy cows subjected
to synchronization of ovulation and timed
insemination. Theriogenology 63 10261037.
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