Effects of Incorporating Spent Bleaching Clay from Palm Oil Refining in the Diets of African Catfish, Clarias gariepinus

Abstract

Spent palm oil bleaching clays contain 20 to 30% adsorbed oil that cannot be recovered economically. A feeding trial was conducted to determine the potential use of this energy-rich oil-laden by-product from palm oil refining in African catfish diets. Seven practical diets containing 0, 5, 10, 15, 20, 25 or 30% SBC were formulated and fed to triplicate groups of African catfish (mean initial weight of 17.9 ± 0.1 g) for 6 weeks. All diets were formulated to be isonitrogenous (35% crude protein) and isolipidic (12% crude lipid). Growth, feed utilization efficiency, survival, body composition, and hematocrits of catfish fed up to 30% SBC were not significantly different (P > 0.05) compared to fish fed the control diet without any SBC. Bone ash tended to slightly increase at dietary SBC levels of 15% and above. Hepatosomatic index of fish fed SBC incorporated diets were significantly lower compared to fish fed the control diet but preliminary histological examination did not reveal any structural abnormalities in the liver cells. Total solids and total suspended solids concentration in tank water increased significantly concomitant to the increasing dietary levels of SBC fed to African catfish. It was concluded that African catfish can be effectively used as a biological agent for the economical extraction of the adsorbed oil in SBC from palm oil refining.