Influence of laurel (Laurus nobilis) essential oil on gut function of Black Sea salmon (Salmo labrax) juveniles

The present work investigated the effects of dietary incorporation of laurel (Laurus nobilis) essential oil on the zootechnical performance and digestive physiology of juvenile Black Sea salmon (Salmo labrax). In this trial, 15 fiberglass tanks (39 × 39 cm square and 33 cm high) were used. Forty-five fish (3.52 ± 0.01 g) were placed randomly per tank. Fish were fed for 90 days with the diet containing 50, 100, 200, or 400 mg kg laurel (Laurus nobilis) essential oils, respectively. The work was performed in the recirculating aquaculture system (RAS) operating with freshwater. Fish were manually fed 3% level of live weight during the experiment period. Final weight (FW), weight gain (WG), feed conversion rate (FCR), and specific growth rate (SGR) were not affected by laurel essential oil supplementation. Dietary laurel essential oil (50 mg kg) affected positively the surface area of fish intestinal villus that required for digestion. Both villus height and villus width were affected positively in fish fed with 50 mg laurel essential oil kg. While incorporation with 100 mg laurel essential oil kg increased the total α-amylase enzyme, 50 mg laurel kg increased lipase enzyme. Moreover, 50 mg laurel essential oil kg increased lactic acid bacteria (LAB) count in fish. Besides, 50 mg laurel essential oil kg reduced the number of total coliform and E. coli.