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Effects of dietary tryptophan levels on growth performance, whole body composition and gene expression levels related to glycometabolism for juvenile blunt snout bream, Megalobrama amblycephala

Author:
Ji, K., Liang, H., Chisomo‐Kasiya, H., Mokrani, A., Ge, X., Ren, M., Liu, B.
Source:
Aquaculture nutrition 2018 v.24 no.5 pp. 1474-1483
ISSN:
1353-5773
Subject:
Megalobrama amblycephala, body composition, carboxy-lyases, dietary protein, feed conversion, feed intake, fish, gene expression, gene expression regulation, glucokinase, glucose-6-phosphatase, growth performance, insulin-like growth factor I, juveniles, lipid content, liver, messenger RNA, protein efficiency ratio, regression analysis, tryptophan, weight gain
Abstract:
To investigate the effects of dietary tryptophan on growth and glycometabolism in juvenile blunt snout bream, 450 fish (initial weight 23.33 ± 0.03 g) were fed six practical diets with graded levels of tryptophan (from 0.79 g/kg to 5.96 g/kg dry matter) for 8 weeks. Results showed that final weight, per cent weight gain (PWG), protein efficiency rate, feed intake and feed conversion ratio (FCR) were significantly improved by 2.80 g/kg diet. The maximum values of protein and ash were observed in 2.80 g/kg diet, while moisture was minimum. Lipid content of fish fed 3.95 g/kg diet was significantly higher than other diets. The highest plasma insulin‐like growth factor‐1 (IGF‐1) content was observed in 0.79 g/kg diet. In the liver, IGF‐1 mRNA levels were significantly downregulated by 2.80 g/kg dietary tryptophan, while glucokinase levels were by 3.95 g/kg, while glucose‐6‐phosphatase and phosphoenolpyruvate carboxykinase mRNA levels showed a converse trend compared with IGF‐1. Based on PWG and FCR, the optimal dietary tryptophan level was determined to be 1.99 g/kg (6.20 g/kg of dietary protein) and 1.96 g/kg (6.11 g/kg of dietary protein), respectively, using broken‐line regression analysis.
Agid:
6123474