This very interesting recent research discovery of an ancient genetic mutation responsible for equine stamina is getting press coverage. The mutation enables equine muscle cells to produce up to five times more energy than the analogous mouse cells can. Additionally, it enables equines to tolerate this increased energy production.
This summary from NPR is quite readable; the academic paper provides an accessible abstract, then gets pretty technical. Those of you who are biologists, enjoy. 
NPR summary: https://www.npr.org/2025/04/04/nx-s1-5349567/unique-genetic-change-horses-athletic-powerhouses
Research paper: https://www.science.org/doi/10.1126/science.adr8589
Hats off to our favorite mutants, the equines!
CR
