The study tested whether adding the antioxidant enzyme catalase to the storage solution could keep camel embryos alive longer at 4 °C. They found a modest, non‑significant boost in pregnancy rates when embryos were stored for 24–48 hours, but no benefit after 72 hours. The hormone gonadorelin was only mentioned as part of the normal breeding protocol, not as a variable in the experiment.

Context Catalase, an antioxidant, prolonged camel sperm survival during storage at 5°C; however, its effect on storage of camel embryos at 4°C is unknown. Aims This study aims to evaluate the possibility of improving pregnancy rates for embryos stored at 4°C for 24-72h in catalase-supplemented media. Methods Embryos recovered from camels flushed 8days after mating were deposited in Eppendorf tubes containing embryo holding media, either supplemented with 500 IU catalase (Group 1) or without supplementation (Group 2). These Eppendorf tubes were placed in an Equitainer and cooled to 4°C. After 24h, 11 embryos in each group were transferred into recipients 7days after gonadotropin-releasing hormone injection, and the remainder was placed in the fridge at 4°C for a further 24 (n =11/group) or 48h (n =11/group) before transfer. Key results A non-significant increase in pregnancy rate was achieved from embryos cooled in media containing catalase compared with the controls at 24 and 48h, although there was no difference at 72h (9/11 (82%) vs 5/11 (45%), 7/11 (64%) vs 2/11 (18%) and 2/11 (18%) vs 2/11 (18%), for with catalase vs controls at 24, 48 or 72h respectively). Conclusions These results showed that there was a tendency for improved pregnancy rates at 24 (82% vs 45%) and 48h (64% vs 18%) of cooling in catalase-supplemented media compared with controls. This improvement was not evident at 72h. Implications The ability to keep embryos at 4°C for 24-48h reduces the need for such tight synchronization between donors and recipients.