By: A. Riasi (PhD in Animal Nutrition & Physiology) riasi.iut.ac.ir

2. Isfahan University of Technology, Isfahan, Iran Advanced Reproductive Physiology (part 4) By: A. Riasi (PhD in Animal Nutrition & Physiology) http://riasi.iut.ac.ir

3. Spermatozoa in female tract • In natural mating semen are introduced in: • Vagina • Cervix • Within the female tract spermatozoa are lost by: • Neutrophils’ phagocytosis • Physical barrier including the cervix

4. Spermatozoa in female tract • Two stages for spermatozoa transportation: • Rapid • Effect of oxytocin secretion • Effect of prostaglandins • Sustained

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

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

7. Spermatozoa in female tract • Higher levels of fertilization promoting peptide (FPP) prevent capacitation • FPP is found in the seminal fluid. • FPP comes into contact with the spermatozoa upon ejaculation. • FPP has a stimulatory effect on adenosine which increases adenylyl cyclase activity in the sperm.

8. Spermatozoa in female tract • Other chemical changes: • Removal of cholestrol and non-covalently bound epididymal/seminal glycoproteins is important. • Increased permeability of sperm to: • Ca2+, HCO3− and K+ • The increase of intracellular cAMP levels.

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

10. 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.

11. Sperm penetration • A series of events take place in AIJ: • Acrosomal reaction • The vesicles sloughed, leaving the inner acrosomal membrane and the equatorial segment intact

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

13. Sperm penetration

14. Sperm penetration • Two different proteins in sperm membrane: • ZBR • Reaction ZBR and ZP3 facilitate the sperm and zonapellucida contact. • ARPR • Reaction of ARPR and ZP3 start the acrosomal reaction

15. Sperm penetration

16. Sperm penetration

17. Sperm penetration • Three changes occur in the oocyte after penetration of vitelline membrane:

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

19. Cleavage

20. Cleavage • Blastomeres formation • Totipotency potential

21. Cleavage Dissociation and reaggregation of morula-stage blastomeres. (A) There is clear evidence for molecular differences between cells (ie, specification) as early as the four- to eight-cell stage [61–71,157,158]; yet, cell fates remain plastic. (B, C) Following dissociation, it is likely that a combination of cell sorting (arrows) and respecification restores the original status of the embryo. (D) Once cell–cell contacts have been reformed, development proceeds from the blastocyst stage. (E) If only ‘‘inner’’ or ‘‘outer’’ (shown) cells are reaggregated, cell sorting (arrows) is still likely to occur. (F) Outer cells remain competent to produce both ICM cells and additional TE cells (curved arrows), as they do in normal development. (G) A combination of cell sorting, regeneration of ICM cells from outer cells, and (potentially) respecification of outer cells to an ICM lineage restores the original status of the embryo. (Adapted from Maureen L. Condic, Stem Cells and Development , 2014 )

22. Cleavage

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

24. 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.

25. 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.

26. 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.

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

28. 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)

29. 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

30. 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)

31. 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

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

33. 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.

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

35. 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.

36. Increase conception rate • Estradiol plus progesterone based protocol • Exogenous P4 (progestins and Melangestrol acetate) has consequences: • Suppresses LH release • Alters ovarian function • Suppresses estrus • Prevents ovulation

37. Increase conception rate • Several studies found that P4 treatment suppress the growing phase of the dominant follicle. • 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.

38. 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 TAI in anestrous cows? • The treatment with equine chorionic gonadotropin (eCG) may be effective.

39. Increase conception rate • Antiluteolytic strategies after AI: • Pharmacological • Mechanical • Nutritional • Management

40. Increase conception rate • Strategies to increase progesterone after AI: • Daily injection of progesterone • Using of progesterone releasing intravaginal device (PRID) during the days 5-9 after AI. • Inducing the formation of accessory corpora lutea using GnRH, LH or hCG and for ovulation of the first wave dominant follicle.

41. Increase conception rate • Effect of estrogen • Estrogen secretion from a large follicle during the days 14-17 after AI may affect embryo survival. • This hormone has a central role in PGF production and luteolysis.

42. Increase conception rate • Some strategies for reducing estrogen after AI: • 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

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

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

45. 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).

46. Increase conception rate

47. Increase conception rate

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

49. 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).

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