Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aquaculture Use of sodium butyrate in the feeding of Arapaima gigas (Schinz, 1822) juvenile Joaldo Rocha Luz a,b , Ana Paula Souza Ramos a,c , José Fernando Bibiano Melo d , Luís Gustavo Tavares Braga a, ⁎ a Postgraduate Program in Animal Science, Laboratory of Nutrition and Fish Feeding (AQUANUT), State University of Santa Cruz (UESC), 45662-900 Ilhéus, BA, Brazil b Federal Institute of Education, Science and Technology Baiano (IFBaiano), Campus Uruçuca, 45680-000 Uruçuca, BA, Brazil c State University of Southwest Bahia (UESB), Campus Jequie, 45206-190 Jequie, BA, Brazil d Federal University of the Valley of Sao Francisco, (UNIVASF), Petrolina, PE, Brazil ARTICLE INFO Keywords: Additive Blood parameters Enzymatic activity Intestinal villi Performance ABSTRACT The objective of this study was to evaluate the sodium butyrate in the feeding of pirarucu juveniles, Arapaima gigas. Seventy - five juveniles of A. gigas (132.07 ± 3.12 g) were distributed in fifteen 310 L- tanks with constant aeration, filtration system and closed water recirculation. A completely randomized design the experiment, with four treatments including sodium butyrate (98%) in the diets (BS0 = control diet without sodium butyrate, BS1 = 0.5 g kg -1 , BS2 = 1.0 g kg -1 , BS3 = 1.5 g kg -1 , BS4 = 2.0 g kg -1 ) with three replicates, and five juve- nile treatment -1 . The fish were fed three times day -1 (8, 12 and 16 h), until apparent satiety, for 45 days. Water quality parameters such as temperature, pH, dissolved oxygen and ammonia were monitored three times in the week. The growth parameters as weight gain, mean feed consumption, feed conversion ratio, specific growth rate, and survival were evaluated. It was performed chemical analysis of the whole body to establish dry matter, crude protein, ethereal extract, ash and gross energy. The hepatosomatic index and viscerosomatic index of juveniles also were evaluated. Histological sections of the intestine showed greater villous height and enzymatic activity of amylase, lipase and nonspecific alkaline protease. The blood plasma of juveniles was analyzed, as the hematocrit, total plasma protein concentration, triglyceride, glucose, and cholesterol. The inclusion of 1.17 g kg -1 of sodium butyrate in diets for A. gigas juveniles improves the growth parameters. This level favors feed conversion ratio increased intestinal villous height, without interfering in the blood parameters, and pro- mote the adaptation of the enzymatic activity of amylase, lipase and nonspecific alkaline protease. Furthermore, it reduces the activity of aspartate aminotransferase and increases hepatic glycogen levels, making the animals more resistant to potentially stressful conditions in the growing environment. 1. Introduction The pirarucu (Arapaima gigas) is an endemic fish of the Amazon basin, with interesting characteristics for the cultivation, as: growth (Imbiriba, 2001), easy adaptability to commercial feed consumption high fillet yield, meat without intramuscular spines, and market de- mand (Cavero et al., 2003a; Castello, 2004; Fogaça et al., 2011). However, it produces is still incipient in view of the advantages men- tioned above, and although recent nutritional studies have provided information about the species (Cipriano et al., 2015, 2016; Magalhães Júnior et al., 2017; Ribeiro et al., 2017), and there are no studies of the use of additives in the growth parameters and health of A. gigas. Organic acids are additives that improve the fish growth and health (Ng and Koh, 2016; Ali et al., 2017; Jesus et al., 2019) and are being studied in several areas of animal nutrition (Lückstädt et al., 2014). Its beneficial characteristics are related to the palatability of the diets (Ramírez et al., 2017), increased protein digestibility (Lückstädt, 2008), growth gain (Liu et al., 2014), inhibition of pathogenic bacteria action (Bolivar et al., 2018), and improvements in immune responses (Hossain et al., 2007). Sodium butyrate has positive effects on the growth of aquatic ani- mals (Ahmed and Sadek, 2014; Liu et al., 2016; Hoseinifar et al., 2017). The performance of this organic salt in the intestine promotes the ab- sorption of nutrients, and have antioxidant characteristics (Wu et al., 2018). It also enables the supply of energy to enteric cells (Hoseinifar et al., 2017), and improves intestinal villi growth (Liu et al., 2014), with https://doi.org/10.1016/j.aquaculture.2019.05.065 Received 19 February 2019; Received in revised form 27 May 2019; Accepted 27 May 2019 ⁎ Corresponding author at: UESC, Jorge Amado Road, Km 16, 45654-245 Ilheus, Bahia, Brazil. E-mail addresses: joaldo.luz@ifbaiano.com.br (J.R. Luz), gbraga@uesc.br (L.G.T. Braga). Aquaculture 510 (2019) 248–255 Available online 28 May 2019 0044-8486/ © 2019 Elsevier B.V. All rights reserved. T