Effect of Poultry By-product Meal as Replacement for Fish Meal in Diets of Gilthead Seabream (Sparus aurata) Juveniles

This study investigated the effects of replacement of fish meal (FM) with poultry by-product meal (PBM) at 55%, 65% and 75% on growth performance and amino acid metabolism of juvenile gilthead seabream (Sparus aurata) with an initial weight of 35.01±0.11 g for 120 days. The study also evaluated protein and amino acid digestibility to determine their influence on protein metabolism in juvenile seabream. The results indicated that partial replacement of FM with PBM in diets of juvenile gilthead seabream is feasible up to 65% without compromising their growth performance, feed consumption and digestibility (P>0.05). Additionally, hepatosomatic (HSI) showed no significant differences between all groups (P>0.05). The viscerosomatic index (VSI) level was at the highest value, whereas the condition factor (K) was at the lowest value in CTRL (P<0.05). The highest feed conversion ratio (FCR) value was in the 75PBM group (P<0.05). However, there was no statistically significant difference between CTRL and the other PBM groups (P>0.05). Similarly, feed intake and whole-body protein content did not significantly differ among dietary groups (P>0.05). The protein efficiency ratio (PER) values suggest that replacing FM with PBM (up to 65%) in diets of juvenile gilthead seabream is effective and produces diets with high-quality proteins and digestibility coefficients comparable to those of the control group (P>0.05). Additionally, amino acid profiles of juvenile gilthead seabream fed with diets containing up to 75% PBM showed no deficiencies in essential amino acids. Nevertheless, we can suggest that 75% PBM substitution for FM can be used in the diets of gilthead seabream, although it causes a slight decrease in growth, FCR and protein digestibility. These results suggest that partial replacement of FM with PBM can be a viable strategy for feeding juvenile gilthead seabream, offering a sustainable advantageous alternative.