Growth and apparent digestibility of nutrients, fatty acids and amino acids in Pacific white shrimp, Litopenaeus vannamei, fed diets with rice protein concentrate as total and partial replacement of fish meal Amin Oujifard, Jafar Seyfabadi ⁎, Abdolmohammad Abedian Kenari, Masoud Rezaei Faculty of Marine Sciences, Tarbiat Modares University, Noor, Mazandaran 46417-76489, Iran abstract article info Article history: Received 15 August 2011 Received in revised form 17 December 2011 Accepted 19 December 2011 Available online 15 January 2012 Keywords: Apparent digestibility coefficient Amino acids Fatty acids Growth Litopenaeus vannamei Nutrition Rice protein concentrate Growth and apparent digestibility coefficients (ADCs) of dry matter (DM), crude protein (CP), crude lipid (CL), gross energy (GE), essential amino acids (EAA), nonessential amino acids (NEAA) and fatty acids (FA) were determined for the Pacific white shrimp, Litopenaeus vannamei. Five isonitrogenous (36.6% protein) diets, formulated by replacing 0, 25, 50, 75, and 100% of fish meal (FM) with rice protein concentrate (RPC), were fed to shrimp (initial weight 6.99 ± 0.08 g) five times daily to satiation for 60 days. ADCs were determined using 0.5% Cr 2 O 3 . Feces were collected from three replicate groups of shrimp. Shrimp fed with 0, 25 and 50% replacements had similar weight increase (P b 0.05), specific growth rate (SGR) and feed con- version ratio (FCR), whereas all the above parameters declined significantly (P b 0.05) as the dietary RPC levels increased above 50%. Survival was high (≥95%) and similar for all diets. ADCs of diets were: CP (52.41–90.52%), CL (80.03–94.11%), GE (55.24–89.41%), EAA (57.39–96.13%), NEAA (41.11–94.74%), SFA (24.61–65.43%), MUFA (41.50–80.45%), and PUFA (57.14–83.90%). Generally, a decreasing trend in ADC for crude protein, crude lipid, gross energy and amino acid (AA) was observed when the RPC level increased. ADC of the FA in shrimp fed with FM and 50% RPC were significantly higher than 25, 75 and 100%. The highest digestibility values were obtained in the FM diet (P b 0.05). The results suggest that RPC can be a potential candidate for FM replacement up to 50%; reduced growth performance was mostly a consequence of reduced digestible nutrients as the RPC level was increased in the diet. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Protein is a major and the most expensive ingredient in shrimp feed and also regarded as a growth limiting factor (Fernández-Gimenez et al., 2009). The most common source of protein in aquaculture is usually fish meal (FM), the supply of which is often limited and generally costly (Tacon et al., 1998; Naylor et al., 2000). Commercial shrimp formula- tions commonly include between 25 and 50% FM (Amaya et al., 2007). The rapid expansion of aquaculture, along with improvements in shrimp culture, has increased the demand for feeds, which mainly de- pend on FM as the major dietary component due to its ideal nutritional quality (Gul et al., 2007). Thus, there is an ever-growing concern to identify the low-cost protein rich ingredients in order to substitute FM with less expensive and more readily available protein sources (Tacon et al., 1998; Naylor et al., 2000). Among such alternatives, rice protein concentrate (RPC) may prove to be a valuable source due to its high pro- tein content (Palmegiano et al., 2006, 2007). Besides, RPC is comparable to FM in protein and fat contents, and higher than many other plant protein sources. Recent studies suggest that RPC may be a good alterna- tive plant protein source of high nutritive quality when included at up to 20% in diets for fish (Palmegiano et al., 2006, 2007). Although the alternative plant proteins are initially selected for being less expensive and more available than FM, it is also necessary to consider plant protein with an adequate balance in amino acid pro- file, good digestibility, high level protein content, and palatability (Sánchez-Lozano et al., 2009). When including plant protein sources, the carbohydrate fraction as well as anti-nutrients may alter digestion and nutrient utilization (Francis et al., 2001; Krogdahl et al., 2005). In addition, use of ingredients as alternatives to FM is limited by unknown availability of nutrients (Riche and Williams, 2010). Diets have been generally evaluated in terms of growth with little attention to the digest- ibility. A feed may contain the adequate amount of nutrients formulated for a species but will just be wasted and detrimental to the environment if not efficiently assimilated. An effective feed can be prepared when in- formation on digestibility of nutrients in feedstuffs has been considered in its formulation (Catacutan et al., 2003). Thus, assessing the nutrient digestibility is the first step in evaluating the potential of an ingredient for use in the diet of reared species (Allan et al., 2000). Digestibility trials evaluate the nutritional value of a feedstuff which provides important information that supplements growth measurements (Akiyama et al., Aquaculture 342-343 (2012) 56–61 ⁎ Corresponding author. Tel.: + 98 912 218 2335; fax: + 98 0122 6253499. E-mail address: jseyfabadi@gmail.com (J. Seyfabadi). 0044-8486/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2011.12.038 Contents lists available at SciVerse ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aqua-online