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Background: The initial stages of development depend on mRNA and proteins accumulated in the oocyte, and during these stages, certain genes are essential for fertilization, first cleavage and embryonic genome activation. The aim of this study was first to search for avian oocyte-specific genes using an in silico and a microarray approaches, then to investigate the temporal and spatial dynamics of the expression of some of these genes during follicular maturation and early embryogenesis. Results: The in silico approach allowed us to identify 18 chicken homologs of mouse potential oocyte genes found by digital differential display. Using the chicken Affymetrix microarray, we identified 461 genes overexpressed in granulosa cells (GCs) and 250 genes overexpressed in the germinal disc (GD) of the hen oocyte. Six genes were identified using both in silico and microarray approaches. Based on GO annotations, GC and GD genes were differentially involved in biological processes, reflecting different physiological destinations of these two cell layers. Finally we studied the spatial and temporal dynamics of the expression of 21 chicken genes. According to their expression patterns all these genes are involved in different stages of final follicular maturation and/or early embryogenesis in the chicken. Among them, 8 genes (btg4, chkmos, wee, zpA, dazL, cvh, zar1 and ktfn) were preferentially expressed in the maturing occyte and cvh, zar1 and ktfn were also highly expressed in the early embryo. Conclusion: We showed that in silico and Affymetrix microarray approaches were relevant and complementary in order to find new avian genes potentially involved in oocyte maturation and/or early embryo development, and allowed the discovery of new potential chicken mature oocyte and chicken granulosa cell markers for future studies. Moreover, detailed study of the expression of some of these genes revealed promising candidates for maternal effect genes in the chicken. Finally, the finding concerning the different state of rRNA compared to that of mRNA during the postovulatory period shed light on some mechanisms through which oocyte to embryo transition occurs in the hen. [ABSTRACT FROM AUTHOR]

Abstract: Egg yolk is normally used as a protective agent to freeze semen of equine and other species. However, addition of egg yolk in extenders is not without disadvantages and the demand to find cryoprotective alternatives is strong. The objective of this study was to test the cryoprotective capacities of liposomes composed of egg yolk phospholipids. Two experiments were conducted: 1) the first to determine the optimal composition and concentration of liposomes to preserve post-thaw motility and membrane integrity of spermatozoa; 2) the second to assess in vivo the cryoprotective capacities of these liposomes. In Experiment 2, post-thaw motility and membrane integrity of spermatozoa were also analyzed. Experiment 1 demonstrated that liposomes composed of phospholipids E80 (commercial lecithins from egg yolk composed mainly of phosphatidylcholine and phosphatidylethanolamine) and of Hank''s salts-glucose-lactose solution (E80-liposomes) were the most efficient in preserving post-thaw motility. The optimal concentration was 4 % (v/v). In Experiment 2, fertility rate after artificial insemination of semen frozen with E80-liposomes was 55 % (22/40) compared with 68 % (27/40) with the control extender containing egg yolk (EY) (p = 0.23). Post-thaw motility parameters were higher with EY than with E80-liposomes (p < 0.0001). For post-thaw membrane integrity no difference was observed between the two extenders (p = 0.08). Liposomes composed of egg yolk phospholipids appeared to be a promising alternative to replace egg yolk in semen freezing extenders in equine species. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to compare fertility and early embryo mortality rates (≤5 days of incubation) following artificial insemination (AI) of common duck females (Anas Platyrhynchos) with semen from either common or Muscovy (Cairina Moschata) drakes at various periods of the reproductive season (Period I, 27–35 weeks; Period II, 39–43 weeks and Period III, 49–56 weeks). Based on observations performed by stereomicroscopy on eggs laid from Days 2 to 10 after AI, we confirmed that fertility was significantly lower in the interbred compared to the purebred cross at each of the periods tested (purebred 58.1, 61.2 and 54.2 versus crossbred 31.0, 40.4 and 39.5 at Periods I, II and II, respectively; 0.01&#60; P &#60;0.001). In a complementary experiment, we demonstrated that the number of perivitelline spermatozoa (NPS) was markedly lower in mule (crossbred) eggs compared to common (purebred) eggs, a strong indication that initial sperm selection occurring in the lower oviduct is probably more intense after crossbred compared to purebred insemination. Comparison of early embryo mortality (EEM) between mule and common duck eggs indicated that increased levels of EEM in mule embryos corresponded to Stages II–IV of the Eyal-Giladi and Kochav classification (EGK). While a similar age-dependent increase in early embryo mortality was observed in eggs from both genetic origins during the latter periods of the reproductive season, it was also established that embryo mortality due to parental age was related rather to Stages X–XIV of the EGK classification in eggs from both genetic origins. It is concluded that the relative subfertility of mule compared to common duck eggs is probably the consequence of a more intense rate of selection of heterologous than homologous spermatozoa occurring in the vaginal portion of the oviduct while the causal origins of EEM in mule duck eggs can at least in part be identified on the basis of precise staging (by stereomicroscopy) of dead embryos. [Copyright &y& Elsevier]