Dietary phenylalanine requirement and tyrosine replacement value for phenylalanine for fingerling Catla catla (Hamilton)

• Published in: Aquaculture 2014-09, Vol.433, p.256-265
• Main Authors: Zehra, Seemab, Khan, Mukhtar A.
• Format: Article
• Language: English
• Subjects: Amino acids; Animal and plant ecology; Animal aquaculture; Animal productions; Animal, plant and microbial ecology; Aquaculture; Autoecology; Biological and medical sciences; Carp; Catla; Catla catla; Dietary supplements; Experiments; Fingerling Catla catla; Fresh water ecosystems; Fundamental and applied biological sciences. Psychology; General aspects; Growth; Phenylalanine; Regression analysis; Requirement; Synecology
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2014.06.023

Two 12-week experiments were conducted to determine the dietary phenylalanine requirement and tyrosine replacement value for phenylalanine for fingerling Catla catla. In experiment I, phenylalanine requirement was determined by feeding six casein–gelatin based amino acid test diets (330gkg−1 CP; 16.72kJg−1 GE) with graded levels of phenylalanine (3.9, 6.4, 8.7, 11.2, 13.8, 16.2gkg−1 dry diet) at a constant level (10gkg−1) of dietary tyrosine to triplicate groups of fish (3.95±0.24cm; 0.68±0.19g) near to satiation. Live weight gain (LWG%), specific growth rate (SGR % day−1), feed conversion ratio (FCR), protein retention efficiency (PRE%), phenylalanine retention efficiency (PHRE%) and RNA/DNA ratio responded positively with the increasing concentrations of phenylalanine reaching the highest values at 11.2gkg−1 of dry diet. Quadratic regression analysis of LWG, SGR, PRE, PHRE and RNA/DNA ratio at 95% of maximum response against varying levels of dietary phenylalanine exhibited the requirement at 10.3, 10.1, 9.9, 9.7 and 10.6gkg−1 dry diet, respectively. The above analysis revealed that inclusion of phenylalanine at 10.1gkg−1 of dry diet, corresponding to 594gkg−1 of lysine is optimum. In experiment II, six diets with different levels of l-tyrosine (1.9, 3.8, 5.9, 8.1, 9.8, 11.8gkg−1 dry diet) with 10.1gkg−1 phenylalanine (determined in experiment I) fixed in all the test diets were fed to fish (3.85±0.25cm; 0.66±0.16g) to determine the tyrosine requirement under identical conditions. Quadratic regression analysis of LWG, SGR, PRE, PHRE and RNA/DNA ratio at 95% of maximum response against dietary tyrosine concentrations indicated the requirement at 6.3, 6.5, 6.5, 7.1 and 7.3gkg−1 dry diet, respectively. Hence, inclusion of tyrosine at 6.8gkg−1 of dry diet, corresponding to 378gkg−1 of lysine is taken as the tyrosine required for optimum utilization of phenylalanine. Based on above data, a total requirement of phenylalanine and tyrosine for fingerling C. catla was found to be 16.9gkg−1 (10.1gkg−1 phenylalanine+6.8gkg−1 tyrosine) of dry diet, corresponding to 939gkg−1 of lysine. Tyrosine replacement value for phenylalanine was computed to be 37% on molar basis. •Phenylalanine and tyrosine requirements for Catla catla•Phenylalanine and tyrosine inclusion at 10.1 and 6.8gkg−1 is optimum to maximize growth.•Phenylalanine may be spared by tyrosine to an extent of 37% on molar basis.