Abstract
Aim of study: To evaluate the effect of the dietary NaCl level for Nile tilapia fingerlings.Area of study: Palotina sector of Federal University of Paraná, in southern Brazil.Material and methods: An experiment was carried using 750 Nile tilapia fingerlings (4.61 ± 0.09 g) distributed in 30 1,000-L circular tanks in a completely randomized design with six treatments and five replicates. NaCl was added to extruded fish meal-free diets at 0.0, 2.5, 5.0, 7.5, 10.0 and 12.5 (g/kg). After the experimental period, fish were submitted to a 24 h-fast and weighed. All data were submitted to an analysis of variance and Tukey’s test followed by Levene’s test and regression test, using the Statistica 7.0® software package.Main results: Fish fed the NaCl-free diet presented better growth performance (p<0.05) compared to the other diets. Linear decrease effects on final weight (y = 50.1754 – 0.1672x, r2 = 0.6984), specific growth rate (y = 45.5418 – 0.1688x, r² = 0.6966), weight gain (y = 4.9465 – 0.008x; r² = 0.6886) and apparent feed conversion (y = 0.7113 + 0.0043x; r² = 0.7655) were noted. Efficiency and apparent protein retention were better in the NaCl-free diet (p<0.05). Significant differences (p<0.05) were observed for fillet fat and crude protein content. Increasing NaCl levels led to significant decreases (p<0.05) in Nile tilapia fingerling protein efficiency rates (y = 3.7804 - 0.0116x; r² = 0.6549).Research highlights: Thus, NaCl should not be included in fish meal-free diets for Nile tilapia fingerlings.
Highlights
Nile tilapia is one of the widely cultivated fish species (Hallali et al, 2018), as it displays adequate zootechnical characteristics and adaptability, is easy to reproduce and presents excellent growth rates when fed both natural and artificial diets, in addition to being resistant to handling and to disease-causing agents (Webster & Lim, 2006).this species forms the basis of aquaculture-based economy worldwide.One of the most important requirements in the production chain is nutrition, which impacts three factors of paramount importance for sustainable aquaculture: feed cost, fish growth and nutrient excretion into the water
The macrophytes started to be removed when they came to cover more than 70% of the biofilter area, The aeration system consisted of a 1 HP air blower connected to PVC pipes and silicone hoses with porous stones at the ends for oxygen distribution to each experimental unit
100 L of water was siphoned from each experimental unit to remove possible feed leftovers, feces and organic matter prior to the last daily feeding event
Summary
Nile tilapia is one of the widely cultivated fish species (Hallali et al, 2018), as it displays adequate zootechnical characteristics and adaptability, is easy to reproduce and presents excellent growth rates when fed both natural and artificial diets, in addition to being resistant to handling and to disease-causing agents (Webster & Lim, 2006).this species forms the basis of aquaculture-based economy worldwide.One of the most important requirements in the production chain is nutrition, which impacts three factors of paramount importance for sustainable aquaculture: feed cost, fish growth and nutrient excretion into the water. Nile tilapia is one of the widely cultivated fish species (Hallali et al, 2018), as it displays adequate zootechnical characteristics and adaptability, is easy to reproduce and presents excellent growth rates when fed both natural and artificial diets, in addition to being resistant to handling and to disease-causing agents (Webster & Lim, 2006). This species forms the basis of aquaculture-based economy worldwide. They can be administered in the form of NaCl, improving dietary palatability and be used as a source of both Na+ (39.74%) and Cl- (60.23%) (Maynard & Loosli, 1974; Borges et al, 1998)
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