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Effect of crude oil extracts from trout offal as a replacement for fish oil in the diets of the Australian native fish Murray cod Maccullochella peelii peelii
journal contributionposted on 2003-07-25, 00:00 authored by Giovanni Turchini, Rasanthi Gunasekera, S De Silva
The efficacy of trout oil (TO), extracted from trout offal from the aquaculture industry, was evaluated in juvenile Murray cod Maccullochella peelii peelii (25.4-0.81 g) diets in an experiment conducted over 60 days at 23.7-0.8 °C. Five isonitrogenous (48% protein), isolipidic (16%) and isoenergetic (21.8 kJ gm1) diets, in which the fish oil fraction was replaced in increments of 25% (0-100%), were used. The best growth and feed efficiency was observed in fish fed diets containing 50-75% TO. The relationship of specific growth rate (SGR), food conversion ratio (FCR) and protein efficiency ratio (PER) to the amount of TO in the diets was described in each case by second-order polynomial equations (P<0.05), which were: SGR=-0.44TO2+0.52TO+1.23 (r2=0.90, P<0.05); FCR=0.53TO2-0.64TO+1.21 (r2=0.95, P<0.05); and PER=-0.73TO2+0.90TO+1.54 (r2=0.90, P<0.05). Significant differences in carcass and muscle proximate compositions were noted among the different dietary treatments. Less lipid was found in muscle than in carcass. The fatty acids found in highest amounts in Murray cod, irrespective of the dietary treatment, were palmitic acid (16:0), oleic acid (18:1n-9), linoleic acid (18:2n-6) and eicosapentaenoic acid (20:5n-3). The fatty acid composition of the muscle reflected that of the diets. Both the n-6 fatty acid content and the n-3 to n-6 ratio were significantly (P<0.05) related to growth parameters, the relationships being as follows. Percentage of n-6 in diet (X) to SGR and FCR: SGR=-0.12X2+3.96X-32.51 (r2=0.96) and FCR=0.13X2-4.47X+39.39 (r2=0.98); and n-3:n-6 ratio (Z) to SGR, FCR, PER: SGR=-2.02Z2+5.01Z-1.74 (r2=0.88), FCR=2.31Z2-5.70Z+4.54 (r2=0.93) and PER=-3.12Z2-7.56Z+2.80 (r2=0.88) respectively. It is evident from this study that TO could be used effectively in Murray cod diets, and that an n-3:n-6 ratio of 1.2 results in the best growth performance in Murray cod.
Pagination697 - 708
PublisherBlackwell Publishing Ltd.
Publication classificationC1 Refereed article in a scholarly journal
Copyright notice2003, Springer
CategoriesNo categories selected
aquatic food industry wastetrout offal oilfish oil replacementfatty acidsn-3:n-6Murray codScience & TechnologyLife Sciences & BiomedicineFisheriesn-3 : n-6FATTY-ACID COMPOSITIONSALMON ONCORHYNCHUS-TSHAWYTSCHAEELS ANGUILLA-ANGUILLADICENTRARCHUS-LABRAXGROWTH-PERFORMANCEMENHADEN OILSHORTFIN EELLIPID LEVELPROTEINMITCHELL