Cymbopogon flexuosus essential oil as an additive improves growth, biochemical and physiological responses and survival against Aeromonas hydrophila infection in Nile tilapia

Elizângela M De Souza,Mateus M Da Costa,Carlos E Copatti,Seldon A De Souza,Anderson M De Souza,José F.B Melo,Renilde C De Souza

doi:10.1590/0001-3765202020190140

Abstract

The objective of the present study was to evaluate growth, biochemical, hematological and intestinal enzymes responses and survival of Nile tilapia juveniles fed a diet containing the essential oil of lemongrass Cymbopogum flexuosus (EOCF) and infected by Aeromonas hydrophila. Five diets were evaluated (in quadruplicate) with increasing levels of EOCF (0.0 - control; 0.25; 0.50; 1.0 and 2.0 mL kg diet-1). On day 45, eight fish per treatment were sampled and blood, liver and intestine samples were taken. Others eight fish per treatment were infected with A. hydrophila followed by a 15-day period of observation. Citral is the main constituent of EOCF. The inclusion of 2.0 mL EOCF kg diet-1 increased specific growth rate and survival after A. hydrophila infection and decreased feed conversion ratio of Nile tilapia. In general, higher concentrations of EOCF in the diet reduced plasma glucose and triglycerides levels, and increased plasma amino acids, alanine aminotransferase (ALT) and hepatic ALT levels, hematological parameters, and the activity of intestinal enzymes. It was concluded that the inclusion of 2.0 mL EOCF kg diet-1 improved growth performance, biochemical and physiological responses and decreased mortality of Nile tilapia after A. hydrophila infection.

Highlights

Nile tilapia (Oreochromis niloticus) is one of the major species of freshwater fish produced in the world (FAO 2018)
Chemical compounds were performed by chromatographic analysis using and Agilent 7890A gas equipment coupled to Agilent 5975C mass selective detector (GC-MS), where were identified 92.48% of the compounds of the essential oil of lemongrass Cymbopogum flexuosus (EOCF)
Previous studies verified the addition of 2.0 mL Aloysia triphylla essential oil kg diet-1 (50.19% of citral) increased silver catfish growth, but it did not affect zebrafish (Danio rerio) growth (Zeppenfeld et al 2016, Zago et al 2018)

Summary

Introduction

Nile tilapia (Oreochromis niloticus) is one of the major species of freshwater fish produced in the world (FAO 2018). The intensification of production in intensive systems can trigger the occurrence of fish diseases caused by opportunistic agents (Martins et al 2008). In this context, the involvement of Aeromonas hydrophila in sickness is usually associated with other conditions, and its pathogenicity appears to be related to environment stress in debilitated hosts (Janda & Abbott 2010). Synthetic antibiotics have commonly been used to treat infections in fish This can trigger selective pressure for the emergence of bacterial resistance, introducing risks to the environment and public health (Bueno et al 2017, De Souza et al 2017, Klatte et al 2017). Based on consumer expectations, the aquaculture industry is expected to reduce the use of synthetic growth-promoting agents in fish diets because of the risk caused to humans by chemical residues in fish

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