221 EFFECT OF ROCKING ON IN VITRO PRODUCTION OF BOVINE EMBRYOS

Abstract

This study tested whether embryo development yield using in vitro fertilization (IVF) could be improved by rocking cultures. Bovine ovaries were obtained at a slaughterhouse and transported to the laboratory within 6 h. Cumulus–oocyte complexes were collected and 20–25 were transferred in 100-μL drops of TCM-199 containing 10% fetal bovine serum and antibiotics under paraffin oil. Maturation was for 20–24 h at 38.5°C under 5% CO₂ and 95% air in a humid atmosphere (IVM). In vitro fertilization was carried out for 6 h using frozen–thawed sperm from a single bull in modified Brackett and Oliphant (BO) medium. Presumptive zygotes were cultured in CR1aa supplemented with 10 mg mL^–1 of BSA or 5% FBS for 9 d at 38.5°C under 5% CO₂, 5% O₂, and 90% N₂ in a humid atmosphere (IVC). Rocking was performed to a height of 6 cm every 7 s using a Profile Rocker (New Brunswick Scientific Co., Edison, NJ, USA) in an incubator. Dishes were placed at a 15-cm distance from the fulcrum of the rocker. The conventional method (no rocking) served as a control, and every experiment was replicated 3 times. For Experiment 1, the effect of the period of rocking on developmental competence was examined when COC or zygotes were subjected to rocking for IVM, IVF, or IVC (IVM-move, IVF-move, and IVC-move). There were no significant differences in rates of oocyte maturation, cleavage, and development for IVM-move v. the control, or for rate of development between IVC-move and the control. However, the rate of fertilization for IVF-move was higher than that of the control (88.9 v. 67.5%; P < 0.01), and the rate of development was higher for IVF-move than for the control (39.0 v. 25.7%; P < 0.05). For Experiment 2, the effect of rocking frequency during IVF on development was determined. The IVF cultures were rocked every 7, 3.5, and 1.5 s (IVF-1move, IVF-2move, IVF-3move). The rates of cleavage on IVF-1move, IVF-2move, IVF-3move, and the control were 74.3, 69.8, 68.8, and 60.4%, and the rates of development were 39.0, 48.3, 26.2, and 25.7%, respectively. The rates of development on IVF-1move and IVF-2move were significantly different from the control and IVF-3move (P < 0.01). These results showed that rocking during IVF improved fertilization and embryo yield, and that frequency of rocking affected embryo development.