44 SEPTEMBER 2015 • WORLD AQUACULTURE • WWW.WAS.ORG stocked into each side of the tank. Fish were reared in a flow-through system supplied with fresh groundwater. Around 80 percent of the water in the system was changed every three weeks. Fish were fed at 2-2.5 percent of their body weight per day. This amount was close to the maximal daily ration for tilapia. Fish were fed manually twice daily at 0800 and 1500 h; the daily ration was divided into two equal meals. Fish were weighed once every 3 weeks to monitor growth performance and adjust feeding rations. Fish were fed for 18 weeks (July 28 to November 30, 2013). Water temperature was recorded daily and other water quality parameters, including ammonia and nitrite concentrations, were determined weekly. At the end of the feeding trial, body length and weight of tilapia were recorded. Weight gain (WG, as measured by the percentage of body weight gain), feed efficiency (FE), protein efficiency ratio (PER), protein retention, condition factor and hepatosomatic index were calculated. Growth performance of tilapia fed different diets are shown in Table 2. The growth rate of tilapia fed LOPRO 26/7+AG was 5.2 percent greater than that of tilapia fed the control diet, although these differences were not significantly different. FCR, protein efficiency ratio (PER) and protein retention of tilapia fed the LOPRO 26/7+AG-diet was better than those of tilapia fed the control diet. These results clearly indicate that supplementation with the feed additive had a positive effect on protein utilization and growth for tilapia, resulting in effective protein sparing. Effects of the Feed Additive on Carcass Characteristics Five fish were sacrificed from a random sample collected at FIGURE 2. Images of histomorphological changes (40x) to the midgut of tilapia fed diets with and without a feed additive for 18 weeks. a-b, CONTROL 28/7; c-d, LOPRO 26/7+AG. IV, intestinal villus; LP, lamina propria; SC, stratum compactum; MU, muscularis. TABLE 1. Diet formulation and proximate composition (%). CONTROL 28/7 LOPRO 26/7+AG Local fish meal 10.88 10.85 Meat and bone meal 2.18 2.17 Soybean meal 13.06 8.77 Rapeseed meal 8.71 8.68 Wheat meal 10.88 10.85 Wheat flour 10.88 10.85 Coconut meal 8.71 8.68 Whole fat rice bran 10.88 10.85 Corn DDGS 19.59 19.53 Salt 0.70 0.69 Local fish oil 2.61 2.60 DCP 0.44 0.43 Premix 0.44 0.43 Choline 0.04 0.04 Oyster shell powder - 4.34 Aquagest OMF - 0.30 Proximate composition Moisture 8.7 8.3 Crude protein 27.8 26.1 Crude fat 7.4 7.4 Ash 8.2 10.4
RkJQdWJsaXNoZXIy MjExNDY=