291 NOVEL OOCYTE SHIPPING AND MATURATION MEDIUM WITHOUT CO₂ GAS PHASE IMPROVES IN VITRO MATURATION AND PREGNANCY OUTCOME IN CATTLE

Abstract

The aim of the present work was to evaluate embryonic development after shipping and maturation of bovine cumulus oocyte complexes (COC) collected by ovum pick up (OPU) in medium (SMM) that does not require CO₂ gas for transport and maturation. Two experiments were conducted, experiment 1 stimulated nonlactating Holstein (n = 4), Jersey (n = 2), Angus (n = 4), and Wagyu (n = 2) donors with 6 pFSH injections (Pluset, MOFA Global LLC, Verona, WI, USA) were used. From each donor, some OPU sessions were delivered the same day (~3 h after collection) for IVM in conventional gas bicarbonate-equilibrated medium system (control), while COC from the other sessions were placed in a portable incubator at 38.5°C, delivered the next day allowing 24 h of maturation in SMM (BoviPro, Mofa Global, WI, USA). The COC were fertilized using commercial semen for each breed, and embryos were cultured in BBH7 medium (BoviPro, Mofa Global, WI, USA) at 38.5°C in 5% O₂, 5% CO₂, and 90% N₂ atmosphere. Embryonic development was evaluated in this experiment. For experiment 2, Day 7 fresh Holstein and Jersey embryos (n = 610) from SMM (n = 550) and controls (n = 60) were transferred in synchronized virgin heifers and pregnancies were diagnosed by ultrasonography at d 35. Data were analysed by ANOVA using GLM, percentages were transformed using arcsin square root, and pregnancy rates were analysed by GenMod using SAS statistical software (Cary, NC, USA). Similar COC numbers were recovered for maturation treatments (P > 0.1; Table 1). The COC matured in SMM had higher cleavage and blastocyst rates than the control group (P < 0.01; Table 1), and this resulted in more transferable embryos per OPU session (P < 0.05; Table 1). We did not find breeds effects or interactions for any variable (P > 0.1; Table 1). After ET, SMM had similar pregnancy rates than control (53.8 v. 58.3%; P > 0.1); however, as more blastocysts were produced per OPU session in the SMM condition, more pregnancies were obtained per session (4.3 v. 2.1; P < 0.01). We conclude that COC matured in SMM had greater oocyte competence than control in commercial settings. The SMM resulted in greater embryonic development, similar pregnancy rates, but more transferable embryos and pregnancies per OPU session than the conventional maturation system.

Table 1.  Least squares means (± SE) of embryonic development of COC matured in SMM or control