Partial and total replacement of fish oil by poultry fat in diets for European seabass (Dicentrarchus labrax) juveniles: Effects on nutrient utilization, growth performance, tissue composition and lipid metabolism

Rendered fats can be sustainable alternatives to fish oil due to their lower price and wider availability. This study evaluates the effects of replacing fish oil by increasing levels of poultry fat (PF) on the nutrient utilization, growth performance, tissue composition and lipid metabolism of European seabass (Dicentrarchus labrax) juveniles. Homogeneous groups of 20 fish (19.1 +/- 2.6 g) were subjected to a 12-h light/12-h dark photoperiod regime and kept in a recirculating saltwater system (salinity 35 parts per thousand, 21 +/- 1 degrees C) for 16 weeks. Triplicate groups of fish were fed a commercial-based diet as control (FO) and four isonitrogenous experimental diets, with 25 (25PF), 50 (50PF), 75 (75PF) and 100% (100PF) fish oil replacement. Soy lecithin was also tested in the diet with 100% PF (100PFL) as an emulsifier agent. The inclusion of PF did not affect nutrient's digestibility nor plasma metabolites at 24 h post-feeding. Final body weight (62-67 g), feed intake, feed conversion ratio, protein efficiency ratio and whole-body composition were similar among experimental diets. Selected lipogenic enzymes' activities were similar among FO and PF diets. The fatty acids profile of muscle, liver and heart reflected the dietary lipid source, decreasing PUFA and increasing MUFA contents with PF inclusion. Fish fed 25PF and 50PF were still able to provide the EPA and DHA muscle levels recommended for human consumption, but 100PF resulted in increased liver lipid accumulation and reduced muscle omega-3 levels. Including soy lecithin could significantly attenuate liver lipid content in fish fed PF-based diets.