Effect of the metalloprotease on growth performance, digestibility and non-specific immune of hybrid tilapia Oreochromis niloticus × O.aureus

The effects of adding different level of metalloprotease in the diet on growth performance, apparent digestibility and non-specific immune of tilapia (Oreochromis niloticus × O.aureus)were investigated. Four different diets were fed to fish for 56 days: a basic diet as control and three diets supplemented with 0.03%, 0.05% and 0.10% metalloprotease. Fish fed with the diet added 0.10% enzyme had significantly higher weight gain and lower feed conversion ratio (FCR) than that of the control group (P < 0.05).Furthermore, the addition of the 0.10% metalloprotease had positive effects on the protein apparent digestibility (P < 0.05) and dry matter apparent digestibility (P < 0.05), and the level of 0.05% also improved the dry matter apparent digestibility significantly (P < 0.05).Superoxide dismutase (SOD) activity in tilapia serum was significantly higher than that of the control group when the fish fed with the diet supplemented with 0.10% metalloprotease.In conclusion, the addition of dietary metalloprotease had significant positive effects on growth performance, protein digestibility and nutrient utilization of tilapia, and enhanced the activities of SOD in tilapia serum.