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(P0.05).Furthermore,the addition of the 0.10% metalloprotease had positive effects on the protein apparent digestibility(P0.05)and dry matter apparent digestibility(P0.05),and the level of 0.05% also improved the dry matter apparent digestibility significantly(P0.05).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.