Evaluation of Citrus limon peels essential oil on growth performance, immune response of Mozambique tilapia Oreochromis mossambicus challenged with Edwardsiella tarda

Highlights

• Citrus limon peel essential oil as an organic waste show enhancement on immune responce in tilapia.

• Increasing disease resistant against Edwardsiella tarda fish pathogen.

• Short term application of Citrus limon peel extract gave a valuable result for fish farms.

• Essential oil to be used for fish fed will be produced economically cheaper than those of other plants.

Abstract

The present study was carried on to determine the effects of Citrus limon peel essential oil as feed supplement on non-specific immune system, disease resistance against Edwardsiella tarda and growth performance in Mozambique tilapia (Oreochromis mossambicus). Fish were randomly distributed at 25 fish per 50 L aquariums and fed with commercial diets supplemented with different ratios (0% for the control group and then 0.5%, 0.75% and 1%) of limon essential oil for 60 days. At the end of the feeding trial, immunological, biochemical and biometrical parameters were assessed. Also following 60 days of feeding, the fish were injected with E. tarda and mortalities were recorded. Results showed that C. limon peel essential oil supplementation diet enhanced the Nitro blue tetrazolium (NBT) positive cell count and total white blood cell (WBC) in tilapia. At the same time a significant change was found in the lysozyme activity and myeloperoxidase activity in serum. Serum glucose, cholesterol and triglycerides decreased while total protein increased in the groups fed with C. limon essential oil supplemented diets. All C. limon peel essential oil supplemented groups showed reduced mortalities following E. tarda infection compared with the control group. The results indicated that C. limon peel essential oil supplementation could improve non-specific immune parameters and growth performance and decrease mortality rate of cultured tilapia.

Statement of relevance

This study determined the effects of an Citrus limon peel essential oil on immune system and resistance to disease in tilapia. The using of essential oil in fish diet prevented tilapia partially from edwardsiellosis disease and increase survival rate also enhance the immune response in fish.

Introduction

Mozambique tilapia, Oreochromis mossambicus, is one of the widely cultured fish species around the world. However, the intensification led to diseases in tilapia culture (Wu et al., 2013). The culture of O. mossambicus in freshwater aquaculture has suffered due to bacterial infections particularly by the occurrence of “edwardsiellosis” caused by Edwardsiella tarda, which results in heavy losses and causes economic loss to fish farmers (Park et al., 2012). This bacterium is also important due to its zoonotic aspects. Infected fish processed for human consumption represents a source of gastroenteritis and meningitis (Janda and Abbot, 1993). Furthermore edwardsiellosis is a generalized septicemia and disease signs may include small cutaneous lesions, distended abdomen, pigment loss, enlarged kidney and abscesses on internal organs (Plumb, 1999). One of the most important purposes in fish production industry is to improve the growth and to control disease. Antibiotics and therapeutants are commonly used for fighting with opportunistic bacteria in aquaculture (Austin and Austin, 2007). But the use of antibiotics lead to antibiotic resistance in bacteria and residue in fish fillet (Esiobu et al., 2002). In recent years, as an alternative to antibiotics, immunostimulant plants or their byproducts are used in aquaculture feed. The most important advantages of natural products are that they neither cause any residue problems nor have any negative effects on fish health or to human and environment. In this study attention focused on Citrus limon essential oil obtained from its peels. C. limon worldwide production is at 4.200,000 t per year (Boluda-Aguilar and López-Gómez, 2013). Limon peels constitute 30–40% of the fruit weight and they are described as waste. A source of health promoting component such as essential oil can be obtained by using this waste. An essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants. C. limon is an important medicinal plant of Rutaceae family. The antibacterial, antioxidant and anticancer effects found in citrus are due to its high content of phenolic compounds particularly limonene. Citrus fruit peels exhibiting antimicrobial activity are rich with flavonoid glycosides, coumarins, β and ɤ-sitosterols, and volatile compounds (Sultana et al., 2007). The volatile compounds are mixtures of monoterpens (limonene), sesquiterpens and sesquiterpenoids such as aldehydes (citral), ketones, acids, alcohol (linolel) and esters (Smith et al., 2001). Recent studies have showed the inhibitory effects of C. limon peel essential oil (CEO) against different pathogens (Nannapaneni et al., 2008, Lee and Najiah, 2009).

It has been reported that several essential oils or natural products, such as Toona sinensis (Wu et al., 2010), Nyctanthes arbortristis (Kirubakaran et al., 2010), Sophora flavescens (Wu et al., 2013), propolis and Aloe barbadensis (Dotta et al., 2014), Chinese herbal mixture (Tang et al., 2014), Astragalus polysaccharides (Zahran et al., 2014), Aloe vera (Gabriel et al., 2015), Citrus sinensis essential oil (Acar et al., 2015), Lippia sidoides and Mentha piperita essential oil (Hashimoto et al., 2016) enhance the non-specific immune response and disease resistance in Nile tilapia.

The aim of the study was to determine the effects of dietary supplementation of limon essential oil on the non-specific immune response and disease resistance of Mozambique tilapia against Edwardsiella tarda pathogen.