Topic: Pak Chong (super napier)vs. native napier

A goat raiser friend has says that after 3 cuttings of Pak chong for feed that the plants lose their vigor and produce less leaf growth.  On the other hand he claims that native napier and dwarf napier grow vigorously after multiple cuttings. So, he no longer is  planting  Pak chong but rather native and dwarf napier instead. 

Has anyone had a similar experience with Pak chong?