High and low performing sires differ in their contributions to early embryonic stress in the bovine.

Context Sires differ in their ability to produce viable blastocysts, yet our understanding of the cellular mechanisms regulated by the sire during early embryo development is limited. Aims The first aim was to characterise autophagy and reactive oxygen species (ROS) in embryos produced by high and low performing sires under normal and stress culture conditions. The second aim was to evaluate DNA damage and lipid peroxidation as mechanisms that may be impacted by increased cellular stress, specifically oxidative stress. Methods Embryos were produced using four high and four low performing sires based on their ability to produce embryos. Autophagy and ROS were measured throughout development. To evaluate oxidative stress response, autophagy, and ROS were measured in 2-6 cell embryos exposed to heat stress. To understand how cellular stress impacts development, DNA damage and lipid peroxidation were assessed. Key results Under normal conditions, embryos from low performing sires had increased ROS and autophagy. Under heat stress, embryos from low performing sires had increased ROS, yet those from high performing sires had increased autophagy. There was no difference in DNA damage or lipid peroxidation. Conclusions Results suggest that embryos from low performing sires may begin development under increased cellular stress, and autophagy potentially increases to mitigate the impacts of stress. Implications There is potential for improving embryonic competence through selection of sires with lower stress-related markers.