Two precursors of taurine have been studied: cysteamine and hypotaurine. Cysteamine has been quantified in genital secretions and found in follicular fluids of all species tested. On the contrary cysteamine was not detected (or traces) in tubal fluids of the same species. Addition of 50, 100 or 250 microM of cysteamine to the maturation medium used in the culturing of bovine oocytes did not improve the cleavage rate nor the embryo's developmental potential in vitro. Furthermore, at 250 microM, cysteamine seems to be toxic to the embryo. Addition of 0.5-1 mM hypotaurine to the bovine embryo culture medium improved significantly blastocyst production and quality. The respective roles of these 2 taurine precursors on maturation and embryo development are discussed.

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This study was initiated to evaluate maternal influence on in vivo and in vitro bovine embryo production and identify animals with contrasted phenotypes for reproductive parameters. Nine Montbéliard cows raised on the same farm and with various genetic origins were included in the study. In vivo-derived embryos were collected nonsurgically from superovulated cows on day 7 after AI (34 collections). Immature oocytes were collected by ovum pickup from the same (superovulated) cows (36 sessions) then matured, fertilized (day 0) with the same bull, and cultured in vitro until day 7 on Vero cell monolayers in B2 medium. Grade 1 to 3 in vivo and grade 1 and 2 in vitro produced embryos deemed viable according to IETS criteria. The mean numbers of blastocysts and viable blastocysts per session per cow were, respectively, 8.3 ± 5.5 and 4.8 ± 3.6 in the in vivo system and 2.5 ± 2.6 and 1.8 ± 2.2 in the in vitro system. Individual cow data of in vivo and in vitro embryo production were analyzed by ANOVA (GLM program in SAS; SAS Institute Inc., Cary, NC, USA). Results are presented in Table 1: mean ± SD. Quantity and quality of produced embryos varied significantly among females, and production in vivo and in vitro was not systematically related. Contrasted phenotypes were identified according to their viable blastocyst rates in both systems (in vivo: no viable/recovered; in vitro: no viable/inseminated). Two females presented a relatively high percentage of viable blastocysts in both systems (over 30% in vitro and over 70% in vivo, Table 1). On the contrary, 2 females showed low percentages of blastocysts in the 2 systems (<10% in vitro and <50% in vivo). For most other females, the percentage of in vivo-produced blastocysts was relatively high (>50%), but in vitro development rates were low. Only one female (C3) presented the inverse situation. Oocytes collected from animals with contrasted phenotypes will be analysed for gene expression to identify marker genes associated with oocyte developmental competence. Table 1. This study was conducted with financial support of ‘Genanimal’ – French Ministry of Research (#03P409) and Apis-Gene.

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