Effects of replacing menhaden fishmeal with cottonseed flour on growth performance, feed utilization and body composition of juvenile red drum Sciaenops ocellatus

Abstract

Low-gossypol cottonseed flour (CSF) is a promising plant protein feedstuff to partially replace fishmeal (FM) in aquafeeds. In the present study, two feeding trials were conducted to evaluate the performance of juvenile red drum Sciaenops ocellatus fed diets with FM substituted by CSF. In feeding trial 1, the Reference diet was formulated to contain 43% crude protein equally contributed by menhaden FM and soy protein concentrate. Five experimental diets were prepared with, 0 (Reference), 25, 50, 75 and 100% of the dietary protein from FM replaced by CSF with lysine (Lys), methionine (Met) and taurine (Tau) supplemented to established requirement levels. In trial 2, the diet with 75% of FM protein replaced with CSF was supplemented with potential palatability enhancers such as glycine, fish solubles, krill meal, inosine monophosphate (IMP) and citric acid. In trials 1 and 2, diets were fed to triplicate groups of juvenile fish with average initial weights (±SEM) of 3.4 ± 0.1 and 23.3 ± 0.3 g/fish for 8 and 6 weeks, respectively. In feeding trial 1, fish responses including percent weight gain (WG), feed efficiency (FE) and protein efficiency ratio (PER) were gradually reduced with increasing levels of CSF substitution, resulting in significant (P < .05) negative linear trends. However, growth responses were not appreciably reduced until more than 50% of the FM protein was replaced with CSF. Condition factor (CF) and intraperitoneal fat ratio also significantly decreased with increasing dietary CSF levels, as did whole-body protein composition. In feeding trial 2, the WG, FE and PER tended to be improved by citric acid and IMP supplementation of the basal diet in which 75% of FM protein was replaced with CSF (CSF75), although the differences did not reach significance (P > .05). The whole-body protein of fish fed CSF75 + IMP diet was significantly (P < .05) higher than fish fed the un-supplemented CSF75 diet. In conclusion, CSF with Lys, Met and Tau supplementation was able to replace up to 50% of crude protein provided by menhaden FM in the diet without drastically affecting growth performance or body composition of red drum. Additionally, supplementation of IMP and citric acid to a diet containing higher levels of CSF tended to improve growth performance of red drum due to enhanced feed utilization.