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¹ Wuxi Fisheries College, Nanjing Agricultural University, Wuxi, China
² Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater
³ Fisheries Research Center, Chinese Academy of Fishery Sciences，Wuxi, China DOI : 10.4194/1303-2712-v15_2_12 Viewed : 4437 - Downloaded : 5514 The effects of feeding-intensity stress on biochemical indices of the GIFT strain of Nile tilapia were investigated in a recirculating freshwater system. Differences in serum and liver biochemistry, routine blood measurements, and growth were examined in fish fed three experimental rations (2%, 4% and 6% of fish biomass daily). Larger rations led to higher SGR but lower FCR, PER and SR. Smaller rations caused higher levels of HSI and cortisol. Fish on the 2% and 6% diets had lower liver levels of C3, LZM, SOD, Glu-GOD, HDL-C, TG, ALP, CAT and higher T4, AST, MDA than those on 4% diets. The 6% group had the lowest levels of LDH, TP, GSH, and GSH-PX. The 2% and 6% groups had lower blood levels of HGB, MCHC, RBC, and WBC than the 4% group; 2% fish had the highest RDW-CV and RDW-SD levels. Therefore, the optimal feeding rate for GIFT tilapia at about 29°C is 4% biomass/day; 6%/day could increase productivity but would be uneconomical; 2%/day would be unsuitable in the absence of natural food. We conclude that high and low feeding intensities would adversely influence the physiological health of tilapia and their resistance to disease, and reduce FCR. Keywords : Nile tilapia, feeding intensity, growth, biochemical index, serum indicator