thanks for the reply. BUt in this case, the leo was borned short tail, will not affect the offspring as wel?
More often than not, deformities, including tail deformities, are developmental anomalies rather than genetic ones. You can breed such a leo unless such a leo starts producing messed up offspring. It will most likely be fine.
I tend not to encourage breeding of deformed animals if I have suitable substitutes, by the way, just to improve my chances of avoiding potential freak occurrences that actually are genetic.