It sounds like the high death rate in your mice could be due to a few things. The D-galactose dose might be too high, especially since it’s given by injection—it can cause serious stress and organ damage if not carefully controlled. The plant extract could also be part of the problem, especially if the dose is too strong or if it was dissolved in something harsh like alcohol or DMSO. Also, if oral gavage isn’t done gently, it can accidentally injure the mice or cause choking. Giving both treatments too close together might also overload their system. I’d suggest checking the doses, spacing out the treatments, using proper controls, and making sure the animals are handled gently and kept in low-stress conditions. A small pilot trial could really help spot what’s going wrong before continuing.