Christine Anthonius, Annita Seok-Kian Yong, and Ching Fui Fui

DOI: 10.14456/sjst-psu.2018.123

pp. 1009 - 1016

Abstract

A feeding trial was conducted in juvenile TGGG hybrid grouper to investigate the growth performance, feed
utilization, and digestibility after citric acid supplementation in a diet that was partially composed of duckweed. Five isoproteic
and isolipidic diets (50% protein, 16% lipid levels) were formulated using Lemna minor and Spirodela polyrrhiza at 5% of
fishmeal protein replacement level with or without 3% of citric acid supplementation. A diet without duckweed and citric acid
was used as the control diet. Triplicate groups of fish (10.30±0.05 g) were randomly distributed in tanks with a flow through
system at a stocking density of 20 fish per tank. The fish were fed twice daily with each experimental diet until apparent satiation
for 10 weeks. As a result, the fish fed a diet with duckweed S. polyrrhiza and citric acid (DSC) achieved significantly higher
growth, body weight gain (BWG) and specific growth rate (SGR) compared to the control group (P<0.05); however, it was not
significantly different with other treatments (P>0.05). The growth, BWG and SGR in fish fed duckweed diets only (L. minor and
S. polyrrhiza) were almost similar with the control without significant differences (P>0.05). Similarly in feed utilization, fish fed
the DSC diet had a better feed conversion ratio, protein efficiency ratio, and net protein utilization without significant differences
(P>0.05) compared to the control. The apparent digestibility coefficient for crude protein and crude lipid, and phosphorus
absorption of DSC and the diet with duckweed L. minor and citric acid were comparable to the control without any significant
differences (P>0.05). Survival was not affected by the experimental diets. This study showed that TGGG can utilize a diet
partially composed of duckweed and better performance was observed with the aid of citric acid.