Aquaculture Nutrition. 2018;24:1729–1737. wileyonlinelibrary.com/journal/anu | 1729 © 2018 John Wiley & Sons Ltd 1 | INTRODUCTION The estimated production of the aquaculture industry for human consumption in 2014 was 73.8 million tons, where the United States with 4.5% of aquatic production was ranked second after Asia with 88.91% (FAO, 2016b). One of the objectives of the aquaculture in- dustry was the domestication of wild species or the use of potential indigenous species with high growth rate, resistance to high stocking density and reproduction in captive conditions (Laure Begout, Kadri, Huntingford & Damsgard, 2012). In this regard, research is being con- ducted on the identification of bionormative indices of the candidate species, such as Schizothorax pelzami, Barbus sharpeyi, Lutjanus johni, Rachycentron canadum, Pampus argenteus and Piaractus brachypomus (Ebrahimi, Kamrani, Heydarnejad & Safari, 2017; FAO, 2016a). Pacu from Characidae family and the Serrasalmidae subfam- ily known as the red pacu has high growth rate, dietary diversity, high resistance to stressful conditions in the breeding environment and the ability to withstand high storage densities (Fernandes, Lochmann & Bocanegra, 2004). In Latin America countries, the amount of pacu production is ranked second after tilapia cultivation (Suplicy, 2007). One of the challenges facing the aquaculture indus- try is to formulate the optimum diet and to determine the inclusion levels of feed ingredients in the diet (Glencross, Booth & Allan, 2007; Safari, Naserizadeh & Mohammadi Arani, 2016; Safari, Shahsavani, Paolucci & Atash, 2014). In this regard, the amount of palatability, apparent digestibility coefficient (ADC) of feed ingredients or diet, growth performance and the rate of nutrient retention, blood bio- chemistry and histopathologic studies are key indicators of feed in- gredients assessment (Glencross et al., 2007). Considering the strategy of the aquaculture industry to the development of fast-growing species, one of the approaches to produce economic aquafeed is the recognition of potential feed Received: 17 October 2017 | Revised: 3 May 2018 | Accepted: 20 May 2018 DOI: 10.1111/anu.12807 ORIGINAL ARTICLE Screening of selected feedstuffs by juvenile pacu, Piaractus brachypomus (Cuvier, 1818) Hossein Nazari 1 | Alireza Salarzadeh 1 | Omid Safari 2 | Maziar Yahyavi 1 1 Department of Fishery, Bandar Abbas Branch, Islamic Azad University, Bandar Abbas, Iran 2 Department of Fisheries, Faculty of Natural Resources and Environment, Ferdowsi University of Mashhad, Mashhad, Iran Correspondence Hossein Nazari, Bandar Abbas Branch, Islamic Azad University, Bandar Abbas, Iran. Email:hnazarishilat@gmail.com Funding information Islamic Azad University; Ferdowsi University of Mashhad Abstract Apparent crude protein (ADC CP ), crude fat (ADC CF ), gross energy (ADC GE ) and phos- phorus (ADC P ) digestibility coefficients of several typical and novel feedstuffs were determined to be utilized in formulated diets of pacu (20.3 ± 5.6 g). The tested feed- stuffs included two fish meals, four terrestrial animal by-products, three plant pro- tein concentrates, six high-protein plant meals and two low-protein plant meals. The values of ADC CP varied in different fish meals ranging from 96.17% for Koli fish meal to 95.17% for Sardine fish meal. The values of ADC CP for plant protein concentrates ranged from 92.17% for wheat gluten meal to 93.17% for corn gluten meal. The val- ues of ADC CP ranged from 50.17% for faba bean meal to 73.43% for spirulina meal. The ADC P ranged from 51.77% for low-protein plant meals to 85.72% for fish meals. A significant ( p < 0.05) linear regression (r 2 = 0.96) was observed among in vivo ADC CP of five feedstuff classes fed to pacu and in vitro ADC CP . Based on these ob- servations, we conclude that pacu as an omnivorous fish tend to utilize nutrient-rich ingredients from high-protein plant meals to fish meals. KEYWORDS feedstuff, in vitro digestion, in vivo apparent digestibility coefficients, phosphorus digestibility, Piaractus brachypomus