Effect of dietary sage (Salvia officinalis L.) on the growth performance, feed efficacy, blood indices, non-specific immunity, and intestinal microbiota of European sea bass (Dicentrarchus labrax)

Adding medicinal herbs to aquafeed is recommended for feasible aquaculture activity. This study tested for 90 days the effect of dietary sage (Salvia officinalis L.) on the growth performance, feed efficacy, blood indices, non-specific immunity, and intestinal microbiota of European sea bass (Dicentrarchus labrax; n = 300 fish). Fish with an initial weight of 12 ± 0.1 g/fish were distributed in five treatments and fed sage at 0, 2, 4, 6, and 8 g/kg. Dietary sage at 2 g/kg diet improved the growth, feed consumption, and growth hormone secretion in European sea bass. The blood parameters in European sea bass fed on experimental diets showed normal levels for healthy fish. Significantly higher lysozyme and phagocytic activities were recorded with sage supplement at the 4 g/kg diet compared to other groups. Regarding overall bacterial count, fish given a sage-free diet (the control) showed more significant microbiota numbers, Vibrio, Escherichia coli, and acid-fermentative bacteria. Remarkably, fish fed on diets fortified with sage displayed lower records of the total bacterial count, Vibrio, and Escherichia coli than the control. Moreover, fish fed a diet enriched with high levels of sage (6 or 8 g/kg) showed increased acid-fermentative bacteria. The regression analysis showed that the optimum quantity of sage at 3.6 – 4.1 g/kg diet is recommended based on the weight gain, specific growth rate (SGR), phagocytic activity, feed conversion ratio (FCR), and lysozyme activity. In conclusion, the dietary incorporation of sage (2 – 4 g/ kg diet) enhanced growth, feed efficacy, blood indices, non-specific immune responses, and sustained healthier gut flora in European sea bass.