Pregnancy rates observed in dromedary camel embryos stored at room temperature (20–24°C) for up to 72 h with and without catalase supplementation

Abstract Background and purpose : In dromedary camels, the short-term holding of embryos prior to delayed transfer is a useful technique. This study aimed to assess a simple method of liquid storage at room temperature (20–24°C) in non-gassed media, for holding embryos in vitro for up to 3 days. Methods : In experiment 1, Day-7 embryos were placed in Eppendorf’s and stored at room temperature with or without 500 IU/mL catalase supplementation for 24 (n = 20, catalase-treated n = 10, control n = 10), 48 (n = 20, catalase-treated n = 10, control n = 10) and 72 h (n = 20, catalase-treated n = 10, control n = 10) prior to transfer into synchronised recipients. In experiment 2, the rates of cellular apoptosis were measured in both catalase-treated and non-treated embryos that were stored at room temperature for 24 (n = 20, catalase-treated n = 10, control n = 10), 48 (n = 20, catalase-treated n = 10, control n = 10) and 72 h (n = 20, catalase-treated n = 10, control n = 10), respectively. In experiment 3, Day-7 embryos were stored at room temperature for 72 h and then subjected to staining with the fluorescent reactive oxygen species (ROS) indicator H2DCFDA to assess ROS generation in both catalase-treated (n = 6) and non-treated controls (n = 6) and these levels were then compared to those measured in fresh embryos (n = 6). Results : Pregnancy rates at days 18 and 60 were similar for both control and catalase-treated embryos at 24 (90% vs 60%; 80% vs 50%, respectively) and 48 h (50% vs 50%; 20% vs 50% respectively). However, whilst pregnancy rates fell to zero at 72 h in the control, acceptable rates were achieved by catalase-treated embryos at this timepoint ( P < 0.05 60% and 50% at days 18 and 60, respectively). Catalase-treatment did not affect embryo size or the morphological scoring of embryos that were kept at room temperature for up to 72 h. However, catalase-treatment significantly reduced the rates of cellular apoptosis observed in embryos at 48 and 72 h of storage compared to controls ( P < 0.05) and reduced levels of ROS generation in embryos that were stored for 72 h ( P < 0.001). Conclusions : This study demonstrates that dromedary camel embryos can be stored in a simple system at room temperature for up to 24 h without detriment to pregnancy outcomes. In addition, supplementation with catalase is beneficial for camel embryos stored at room temperature beyond 24 h and reduces levels of apoptosis and the generation of ROS in stored embryos.