Oilseed protein such as soybean meal has been used with varying degrees of success as a replacement for fishmeal in diets for many species. Freshwater fish such as blue catfish Ictalurus furcatus as well as marine finfish such as seabass Lates calcarifer were reported to accept some degrees of soybean meal sustitution. One of the oilseed protein sources available in large quantities in Malaysia is palm kernel cake (PKC). As such, PKC could have the potential to be incorporated in aquaculture diet similarly.
The development of cost-effective diets, with increased amounts of locally available raw material is an urgent priority for fish and crustacean aquaculture industries in Malaysia. Typically, the PKC contains from 15 to 18% protein, 3 to 9% lipid, 4 to 5% ash and up to 17% fibre; selected lines higher in protein and lower in fibre and fat are available in large quantities as renderers respond to the need to produce PKC more suitable for use as ruminant feed. Compounded feeds for carnivorous fish presently contain from 50 to 70% by weight of fishery product. Since the raw PKC contains a low level of protein, the potential to replace fishmeal in carnivorous fish such as grouper is not possible. Thus, the aim of this experiment is to use PKC and replace plant protein source such as soybean meal and wheat meal usually incorporated in aquaculture diet.

A 65-day feeding trial was conducted to evaluate the effect of using palm kernel cake (PKC) as feed ingredient in grouper Epinephelus suillus diet. There were 3 formulated diets used (Table I). The diets were formulated such that the inclusion of PKC levels were at 0% (Diet 1), 15% (Diet 2) and 30% (Diet 3). All diets were kept isonitrogenous and isolipid at around 42% and 9% lipid respectively. The chemical composition of the experimental diets is shown in Table II. The trial was conducted in replicate using 6 front-glass fibreglass aquarium tanks with 150-L working capacity each. Every aquarium tank was fully aerated and provided with flow-through brackishwater supply system. Grouper juveniles with 38.8 ± 7.1g (mean ± standard deviation) body weight were randomly stocked in the