WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2015 45 (JUMP TO PAGE 48) the end of the growth trial. Liver, blood and muscle were collected and stored in -20 C until analysis. Midgut samples were analyzed by histological assay. Blood was examined for hematological parameters, including red blood cell count, hematocrit and hemoglobin concentration and plasma triglyceride concentrations. Proximate composition of muscle was also measured. Thirty fish were transferred to Hung-Yi Frozen Food Factory, Pingtung, Taiwan to determine fillet and visceral fat yields (Fig. 1). Tilapia fed LOPRO 26/7+AG had 7.1 percent less visceral fat (Table 3) and 14.0 percent less triglyceride (Table 4) compared to fish fed the control diet. The feed additive ingested by tilapia enhanced lipid utilization and decreased the metabolism of protein to energy. In addition, hepatic glucose-6-phosphate dehydrogenase (G6PDH) activity was greater in fish fed the LOPRO 26/7+AG diet compared to that of fish fed the control diet (Table 4). This enzyme is involved in the pentose phosphate pathway to generate the coenzyme NADPH for energy metabolism. High levels of G6PDH generally indicates high rates of fatty acid synthesis derived from carbohydrate. Enhanced G6PDH activity indicated a greater rate of carbohydrate utilization in tilapia fed diets with the feed additive. The improvement of nutrient utilization was also reflected in fillet yield. Tilapia fed LOPRO 26/7+AG had a 1.1 percent greater fillet yield (Table 3) compared to control fish. TABLE 2. Growth performance of tilapia fed diets with and without a feed additive for 18 weeks. CONTROL 28/7 LOPRO 26/7+AG % change vs control Survival (%) 93±2 96±3 +3.2 Initial wt (g) 177±2 175±2 -1.5 Final wt (g) 470±13 482±12 +2.6 Daily weight gain (g/d) 2.32±0.11 2.44±0.03 +5.2 Feed intake (g/fish) 861±22 840±17 -2.4 FCR 2.95±0.20a 2.74±0.04b -7.1 PER 1.22±0.08a 1.40±0.02b +14.8 Protein retention (%) 27.7±1.7a 29.7±0.0b +7.3 Values are means ± SD from three groups of fish (n=3) with 45 fish per group. Different superscripts in a row indicate a significant difference (P<0.05) between dietary treatments. FCR: feed conversion ratio; PER: protein efficiency ratio. TABLE 3. Hepatosomatic index, condition factor, visceral fat content and fillet yield of tilapia fed diets with and without a feed additive for 18 weeks. CONTROL 28/7 LOPRO 26/7+AG % change vs control Hepatosomatic index (%) 3.3±0.7 3.1±0.3 -6.4 Condition factor 1.88±0.14 2.02±0.04 +7.4 Visceral fat (%) 6.3±1.8 5.8±1.6 -7.6 Fillet yield (with skin) 41.5±0.2 41.9±0.4 +1.1 Fillet yield (without skin) 34.8±0.1 35.2±0.3 +1.1 Values are means ± SD from three groups of fish (n=3) with 5 fish per group. TABLE 4. Hematological parameters of tilapia fed diets with and without a feed additive for 18 weeks. CONTROL 28/7 LOPRO 26/7+AG % change vs control White blood cell (103/μl) 235±11 236±12 Red blood cell (106/μl) 2.55±0.08 2.50±0.24 Hematocrit (%) 33±2 32±3 Hemoglobin (mg/dl) 10.1±0.6 10.6±0.8 Hepatic G6PDH 163±40a 267±29b +63 Plasma triglyceride (mg/dl) 15.7±0.4a 13.5±0.8b -14.0 Values are means ± SD from three groups of fish (n=3) with 3 fish per group. Different superscripts in the row indicate significant differences (P<0.05) between dietary treatments.
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