Poultry By-Product Meal As an Alternative to Fish Meal in the Juvenile Gilthead Seabream (sparus Aurata) Diet

The aim of the present study was to evaluate the eventual possibility of fish meal (FM) substitution in the diet of farmed gilthead seabream (Sparus aurata) by poultry by-product meal (PBM) and to verify PBM suitability in aquafeeds. Inclusion of PBM in the seabream diet was therefore investigated by a multidisciplinary analysis to evaluate its possible effects on fish growth performance, fish welfare and fillet quality. A control diet and two experimental diets, Feed A and Feed B containing PBM with 50% and 100% of FM substitution respectively, were formulated. All diets were isoproteic (45%), isolipidic (20%) and isoenergetic. The growth trial lasted 110 days, including 20 days of fish acclimatization. Juvenile gilthead seabream with an initial average weight of 73.57 +/- 10.47 g were allotted at random in nine tanks (three replicates per diet), fed once a day by hand (feeding rate 1%). As a result, average weight gain increased in all fish groups without any statistically significant difference (P > .05). Measured zootechnical parameters were similar among fish groups, the condition factor as an indicator of fish condition was around 2 and the survival rate was 100%. Investigations through haematological parameters, digestive enzymes and liver histology analyses demonstrated that no statistical difference existed among dietary treatments and this clear evidence attests that PBM inclusion in seabream diets did not have a negative effect on fish welfare. Protein patterns obtained from fish fed the control diet and PBM diets showed a similar expression of structural proteins such as actin, tropomyosin, myosin light chain 1 (MLC1), myosin light chain 2 (MLC2) and fast skeletal myosin light chain (MLC3). Results for fish fillet compositions were comparable in all fish groups with some exceptions for fatty acid composition. The gross energy content of seabream muscle was also not affected by PBM. The present study demonstrated that the total substitution of FM with PBM in the commercial diet of gilthead seabream (S. aurata) is achievable without compromising fish growth performance, fish welfare and fillet quality and suggests that PBM could be considered as a good sustainable raw material for fish food.