Correlation between lipid levels of feed and liver morphology characters of juvenile tilapia (Oreochromis niloticusO.aureus)

The correlation between diet lipid levels and liver morphology and histology of juvenile tilapia (Oreochromis niloticusO.aureus) were studied. The juvenile tilapia were fed five diets with graded lipid levels of 0%, 2%, 4%, 6%, 8%, respectively, for 70 days. The results showed that weight gain rate (WGR) and condition factor (CF) increased first and decreased later with the growing lipid content level. The feed conversion ratio (FCR) decreased first and increased later contrarily. The color and volume of liver and gallbladder of tested fish were different for different lipid content diets. Liver cells diameter increased continuously with the growing lipid content level. Liver cells diameter of group 4 and 5 were significantly larger than that of groups 1, 2 and 3. The symptom of fatty liver disease was appeared obviously in group 4 and 5. Liver cells shifted normal location. Fatty roundels increased in liver cells. And liver cells were translucent and like vacuole. Juvenile tilapia formed fatty liver disease easily if diet lipid content exceeds 6%. It suggested that the supplement of over 4% lipid in diets of juvenile tilapia would be harmful for fish liver.