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.  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 Spermatozoa in female tract

4.  Two stages for spermatozoa transport: Rapid transport Oxytocin secretion Prostaglandins Sustained transport Spermatozoa in female tract

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

7.  Sperm capacitation: Chemical changes  Remove decapacitation factors  Remove cholesterol  Membrane ions changes Physical and morphological changes Spermatozoa in female tract

8.  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. Spermatozoa in female tract

9.  Other chemical changes: Removal of cholestrol and non-covalently bound epididymal/seminal glycoproteins is important. The result is an increased permeability of sperm to Ca 2+, HCO3− and K+ An influx of Ca 2+ produces increased intracellular cAMP levels. Spermatozoa in female tract

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

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

12.  Physical and morphological changes: Spermatozoa in female tract

13.  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. The oocyte moving in female tract

14.  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. Sperm penetration

15.  A spermatozoon has to penetrate four layers before it fertilizes the oocyte: Sperm penetration

20.  Three changes occur in the oocyte after penetration of vitelline membrane: Sperm penetration

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

23. Cleavage

26.  Embryonic mortality in the initial seven days of gestation: Fertilization failure Genetic defects Impaired embryonic development Increase conception rate

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

28.  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. Increase conception rate

29.  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. Increase conception rate

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

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

32.  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) Increase conception rate

33.  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 Increase conception rate

34.  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) Increase conception rate

35.  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 Increase conception rate

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

37.  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. Increase conception rate

38. One possible hormone injection and TAI schedule for the Presynch/Ovsynch protocol based on the results of Moreira et al., 2000 Increase conception rate

39.  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. Increase conception rate

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

41.  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). Increase conception rate

42.  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). Increase conception rate

43.  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. Increase conception rate

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

45.  Antiluteolytic strategies: Pharmacological Mechanical Nutritional Management Increase conception rate

46.  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. Increase conception rate

47.  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. Increase conception rate

48.  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 Increase conception rate

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

50.  Antiluteolytic strategies: Antiinflamatory drugs Fat feeding Bovine somatotropin (bST) Increase conception rate

51.  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). Increase conception rate

52.  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. Increase conception rate

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

54.  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). Increase conception rate

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

56.  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. Maternal recognition of pregnancy

57.  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. Maternal recognition of pregnancy

58.  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. Maternal recognition of pregnancy

59.  The ways in which different species: In human  Luteolysis is initiated by an intraovarian mechanism, although many believe it requires local production of PGF2α. Maternal recognition of pregnancy

60.  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 PGF2α Maternal recognition of pregnancy

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 PGF2α 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 PGF2α. Maternal recognition of pregnancy

65.  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 Maternal recognition of pregnancy

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

67.  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. Embryonic loss

68.  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. Embryonic loss

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

70.  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 Embryonic loss

71.  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. Pregnancy-Associated Glycoproteins (PAG)

72.  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. Pregnancy-Associated Glycoproteins (PAG)

73.  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. Pregnancy-Associated Glycoproteins (PAG)

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

75.  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 Pregnancy-Associated Glycoproteins (PAG)

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. 85:122–131. 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: 945–954. 3- De Rensis, et al. 2008. Inducing ovulation with hCG improves the fertility of dairy cows during the warm season. Theriogenology 69: 1077–1082 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: 1026–1037.