Advanced Reproduction Physiology (Part 3)

1. Advanced Reproduction Physiology(Part 3) Prepared by: A. Riasi http://riasi.iut.ac.ir Isfahan University of Technology College of Agriculture, Department of Animal Science

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)