Effects of dietary supplementation with organic acids mixture on growth, feed efficiency, hematobiochemical parameters, immunity, and intestinal microbiota of Gilthead seabream (Sparus aurata) juveniles

This trial assessed for 90 days the influences of dietary organic acids mixture (Aquagest (R) OM) on the perfor-mance of Gilthead sea bream (Sparus aurata; n = 360; initial weight= 9.15 +/- 0.10 g). A diet without organic acids supplement was specified as control (D0), whereas another five diets were supplemented by 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% for diets D1, D2, D3, D4, and D5, respectively. The fish fed on the control diet [D0] and 0.5% organic acids mixture-based diet [D5] exhibited the lowest final weight [Wt.90], weight gain [Wt.G.], average daily gain [A.D.G.], specific growth rate [S.G.R.], and feed intake [F.I.], as well as the highest feed conversion ratio [F.C.R.]. In comparison, the best results were with 0.2% and 0.3% organic acids mixture-based diets [D2 and D3]. The condition factor (K) rises when the amount of organic acid mixture in the diet is increased >= 0.2% [D2 - D5]. At the same time, the highest hepatosomatic indices [H.S.I.] were in the D5 and D1 groups. Furthermore, the lowest values for hemoglobin, hematocrit, and red blood cells [RBCs] were observed in fish fed a basal diet, and the highest records were in fish-fed D2 and D3 diets. The best lysozyme and phagocytic activities were in D2 and D3 groups. Regarding total bacterial count, Vibrio, and Escherichia coli, fish given a basal diet (D0) showed the highest microbiota records, while fish fed on diets fortified with organic acids exhibited lower counts. No alterations between the experimental groups in body proximate composition, white blood cells [WBCs], total proteins, alanine transaminase [ALT], aspartate transaminase [AST], albumin, urea, creatinine, and acid-fermentative bacteria counts. In conclusion, based on the polynomial regression analysis of S.G.R., F.C. R., lysozyme activity, and phagocytic activity on organic acids levels, the optimal levels of the organic acids mixture ranged from 0.18% to 0.28%.