Preliminary study on effects of methionine hydroxy analog and taurine supplementation in a soy protein concentrate-based diet on the biological performance and amino acid composition of rainbow trout [Oncorhynchus mykiss (Walbaum)] Abstract A feeding trial was conducted on the effects of methionine hydroxy analog (MHA) and taurine supplementation in diets with high levels of soy protein concentrate (SPC) on the growth performance and amino acid composition of rainbow trout, Oncorhynchus mykiss (Walbaum) comparing with fish meal based diet. The control diet had 520 g kg À1 fish meal. In the methionine deficient diets (5.1 g kg À1 ), fish meal was replaced by 490 g kg À1 of the SPC in the SPC49 diet. The SPC49 diet was supplemented with either MHA (6 g kg À1 ) only or a combination of MHA and taurine (2 g kg À1 ). Fish were fed isoproteic (460 g kg À1 ) and isolipidic (130 g kg À1 ) diets for 12 weeks. Growth performance (i.e. weight, feed conversion ratio, and thermal-unit growth coefficient) was inferior in fish fed the SPC49 diet. MHA supplementation improved growth performance (P < 0.05). No difference was observed when taurine was added to the SPC49 and MHA diet (P > 0.05). Whole-body taurine contents increased with taurine supplementation, whereas plasma methionine increased with MHA supplementation (P < 0.05). In conclusion, the substitution of fish meal with SPC supplemented with MHA did not negatively impact growth, and the addition of taurine did not improve growth performance in rainbow trout.

A 12-week feeding trial with Asian sea bass Lates calcarifer juveniles was conducted to evaluate the response of feeding defatted Superworm (Zophobas morio) larval meal on growth performance, feed utilization, apparent digestibility coefficient of nutrients and haemato-biochemical status for Asian sea bass. Five isonitrogenous (450 g/kg) and isolipidic (125 g/kg) experimental diets were formulated. A basal diet that contained no insect meal from defatted Superworm (DFSM) served as the control. Four diets were formulated where DFSM was included at 30 g/kg; 11.11% (DFSM-3), 60 g/ kg; 22.22% (DFSM-6), 90 g/kg; 33.33% (DFSM-9) and 120 g/kg; 44.44% (DFSM-12), respectively, on a dry matter basis. All essential amino acids (EAA) except methionine, phenylalanine and threonine in DFSM compared favourably with fishmeal (FM) and arginine, histidine, isoleucine, leucine, tryptophan and valine were higher than that of FM. No significant (p > .05) differences in weight gain, specific growth rate and feed conversion ratio, hepato-somatic and viscera-somatic index were apparent among fish fed different levels of DFSM. Furthermore, no significant (p < .05) differences were found for apparent digestibility of dry matter (DM) and crude fat in response to dietary DFSM with different levels. A significant decreased linear relationship in the ADC of protein (p = .042) was noted as the level of DFSM incorporation increased in the experimental diet. No significant differences in haematocrit, MCHC and creatinine values were found among the experimental diets. However, a significant quadratic increase in haematocrit (p = .039) was detected as the level of DFSM increased in the diet. Serum cholesterol, alkaline phosphatase (ALP), glutamic pyruvic transaminase (GPT) and glutamic oxaloacetate transaminase (GOT) were linearly reduced with the increasing of dietary DFSM (linear, p = .043; p = .023; p = .018; p = .028). The findings of the present study indicated that growth, feed efficiency and haemato-biochemical indices were not adversely affected by partial substitution of FM up to 120 g/kg dietary inclusion of Superworm meal. We discuss this in the context of aquafeed applications for marine fish production in Asia for more sustainable production using novel protein ingredients and wider implications.

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