Effect of the metalloprotease on growth performance, digestibility and non-specific immune of hybrid tilapia Oreochromis niloticusO.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. 