Haemoglobin powder as a dietary fish meal replacer in juvenile Japanese eel, Anguilla japonica (Temminck et Schlegel).
In the first 6-week experiment, 30 groups of 20 fish each, mean weight 12.8 g, were fed on protein (50% CP) diets in which fish meal was replaced with haemoglobin powder (BM); diet 1 (0% BM, control), diet 2 (12.5% BM), diet 3 (25% BM), diet 4 (50% BM), diet 5 (75% BM), diet 6 (100% BM), diet 7 (25% BM + 3 essential amino acids (EAA)), diet 8 (50% BM + 3 EAA), diet 9 (75% BM + 3 EAA) and diet 10 (100% BM + 3 EAA). Fish were fed daily at a fixed feeding rate of 6% (DM basis) of total body weight. At the start of the second 6-week experiment, the fish were redistributed into individual aquaria as groups of 20 fish and maintained on their earlier diets; their feeding rate was gradually increased to 8% ad libitum. In the first 6-week period, results were not consistent with the treatments, and fish showed poor adaptation to the experimental diets and conditions. In the second 6-week period, liveweight gain, specific growth rate, protein efficiency ratio and protein productive value of fish fed on diets 2, 3, 4, 7, 8 and 9 were not significantly different from those of fish fed on the control diet. However, feed conversion efficiency of fish fed on diets 6 and 10 was lower than that of fish fed on the control diet (P<0.05). It is concluded that fish meal can be replaced by up to 50% haemoglobin powder without supplementation of essential amino acids, and up to 75% with supplementation, in juvenile Japanese eel diets.