OPTIMUM PROTEIN REQUIREMENTS AND OPTIMUM RATIO BETWEEN ANIMAL PROTEIN TO PLANT PROTEIN IN FORMULATED DIETS FOR NILE TILAPIA (TILAPIA NILOTICA L.) (SOYBEAN CONCENTRATE, ANCHOVY FISH MEAL, DIGESTABILITY, SEMI-PURIFIED DIETS, FISH NUTRITION).

摘要

The first of three sequential feeding trials with Tilapia nilotica determined the optimum dietary protein level using eight formulated, semi-purified diets containg casein and gelatin as sources of protein. The protein content in the diets varied from 15 to 50% in 5% increments. The energy content in each diet was 3110 KCal ME/Kg diet. The trial lasted ten weeks. The results indicated that 35% protein level maximized the net protein deposition and net energy deposition and, thus, produced fish having higher nutritional values.; The second feeding trial determined the growth responses of the fish to seven formulated diets containing increasing ratios of anchovy meal (AFM) to soy protein concentrate (SPC) with similar total protein levels, i.e., 35%. The energy contents of each diet was adjusted to 3110 KCal ME/Kg diet. The proportions of AFM to SPC in the dietary protein were graded so that each ingredient provided similar levels of 100, 90, 75, 50, 25, 10 and 0%. A semi-purified diet containing casein and gelatin as the protein source (35% protein) was used as a control. The results indicated that the ratio of 90% SPC to 10% AFM in the dietary protein was the best. That ratio produced the best growth rate, food conversion, food efficiency ratio, protein efficiency ratio, apparent-net protein utilization and net protein deposition.; The third feeding trial was conducted in two sections (A and B), to assess the digestibility of the test diets used in the second feeding trial. The fish were fed the test diets mixed with an 0.5% chromic oxide indicator, and the fecal materials were collected. The results indicated that T. nilotica digested and utilized the soy protein concentrate more efficiently than they did the anchovy meal.