Comparison of the digestive enzyme activity of Nile tilapia (Oreochromis niloticus)in different farming modes

To understand the impact of farming mode on digestive enzyme activity of tilapia,we selected three familiar breeding patterns in Guangdong province,i.e.traditional farming mode(M1),twice harvest a year farming mode(M2)and polyculture of fish and shrimp farming mode(M3).We performed water quality monitoring and digestive enzyme activity detection through the four months observation.M2 model showed the highest stomach protease activity(SPA)in both 1^st and 2^nd months.M1 mode displayed the highest intestinal protease activity(IPA)during the whole observation period.For the hepatopancreas protease activity(HPPA),M2 mode was rather high in the 2^ndmonth as well as the 3^rd month,while M3 model showed the highest level in both 1^st and 4^th months.In terms of each model,the protease activity displayed in the order of IPA>SPA>HPPA.Lipase activity and amylase activity of intestine and hepatopancreas were overall highest in M2 mode.The ability of protein digestion of tilapia in different organs is different,but no significant difference for total protein digestion ability among the three breeding patterns.On the other hand,M2 mode showed advantage in digestion of fat and starch which would reduce the demand of protein in feed composition and further improve the feed conversion ratio and cut down the cost of feed.