Similarly, Lin et al. (2007) investigated the effects of supplemental
exogenous enzymes (protease, β-glucanase and xylanase) at a dose of
1.0 and 1.5 g kg−1 on growth performance of juvenile hybrid tilapia
(Oreochromis niloticus × Oreochromis aureus) fed diets with plantbased
feedstuffs (soybean, rapeseed and cottonseed meals). The results
showed that specific growth rate, feed efficiency ratio and apparent
protein retention significantly improved with increasing dietary
enzyme levels. Moreover, the authors reported that both protease and
amylase activities in the intestine and the hepatopancreas of juvenile
hybrid tilapia significantly increased with increasing dietary enzyme
levels. These results suggest that exogenous enzyme supplementation
can promote the secretion of endogenous enzymes by the fish.