Aquaculture Reports (Jun 2022)
Effects of graded dietary lipid levels on growth performance, fatty acid profile, and hematological characteristics of hybrid pufferfish (Takifugu obscurusｘT. rubripes) juveniles
Abstract
Determination of nutrient requirements for a cultured fish species is necessary to develop a nutritionally-balanced and cost-effective diet because feed contributes greatly to aquaculture operation costs. Lipids are crucial nutrients that provide essential fatty acids, phospholipids, and energy. Thus, the current study was conducted to determine an optimum dietary lipid level for juvenile hybrid pufferfish (Takifugu obscurus ♀ × T. rubripes ♂). Five isonitrogenous diets were prepared to contain various lipid levels at 6%, 9%, 12%, 15% and 18%, resulting in the corresponding protein-to-energy ratios as 29.8, 28.5, 28.0, 26.9, and 25.8 g/MJ, respectively. Three hundred juveniles weighing 4.18 ± 0.08 g (mean±SD) were randomly distributed to 15 tanks, resulting in 20 fish per tank (three replicates per treatment). The feeding trial lasted for 8 weeks. At the end of the trial, final weight, feed intake, weight gain, and specific growth rate of the fish fed 9% and 12% lipid diets were significantly higher than those fed 15% and 18% lipid diets (P < 0.05). Whole-body lipid contents significantly increased with the increasing dietary lipid level, whereas no difference in whole-body moisture, protein, and ash contents in response to the various dietary lipid levels was detected. There was a pattern in the fatty acid profile showing that pooled saturated fatty acid and n-3 polyunsaturated fatty acid levels decreased as the dietary lipid level increased. The fish fed the 12% lipid diet showed a significantly lower aspartate aminotransferase activity in comparison to those fed the 6% and 18% diets. According to the broken-line regression analysis, the optimum dietary lipid level and protein-to-energy ratio were estimated to be 10% and 28.5 g/MJ, respectively.
