Effects of total replacement of fish oil by vegetable oils in the diets of sharpsnout seabream ( Diplodus puntazzo)

Abstract

The aim of this study was to determine the impact of dietary replacement of fish oil by vegetable oils on sharpsnout seabream growth, nutritive utilization, somatic parameters, body composition, feed digestibility, and muscle fatty acid profile, as well as to make an estimate of its economic repercussions. To this end, three isonitrogenous (48% crude protein) and isoenergetic (23 MJ/kg) experimental diets were formulated, using three different lipid sources: fish oil (FO), soybean oil (SO) and linseed oil (LO). These diets were fed to triplicate groups of 30 sharpsnout seabream with an initial average weight of 14.9 g, three times a day to apparent satiation, over 92 days at 24.6 ± 1.1 °C. Our results show that the replacement of fish oil with soybean or linseed oil in sharpsnout seabream diets does not affect growth or feed utilization after three months of feeding. Fish on an SO diet exhibited higher hepatosomatic indices, whereas fillet percentages were significantly lower in fish that had been fed an FO diet. Apparent digestibility coefficients for dry matter, crude protein and crude lipid were significantly lower in fish that had consumed an LO diet. The muscle fatty acid composition reflected that of the diet. Consumption of vegetable oils reduced the muscle content of ARA (arachidonic acid), EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) to a lower degree than their corresponding reductions in the diet after fish oil replacement, which highlights their importance. Vegetable oils also increased the muscle content of linoleic and linolenic acids. In terms of economic performance, the SO diet was the least expensive diet, and had the best economic conversion ratio.