Dietary palm oil level affects growth performance, protein retention and tissue vitamin E concentration of African catfish, Clarias gariepinus

Abstract

A 9-week feeding trial was carried out to determine the effect of increasing dietary palm oil levels on growth, protein utilization efficiency and body composition of African catfish. Seven isonitrogenous and isoenergetic practical diets were formulated to contain 4%, 8%, 12% or 16% refined, bleached, deodorized palm olein (RBDPO) or 8%, 12% or 16% crude palm oil (CPO), in addition to a control diet which was not supplemented with palm oil. Growth performance of African catfish responded significantly ( P<0.05) in a positive manner to palm oil additions of up to 8% and no further improvement in growth was observed with higher levels of palm oil supplementation in the diet. Growth and protein utilization efficiency of African catfish fed diets with RBDPO or CPO at the same inclusion level were not significantly different. Significantly higher nitrogen retention was observed in catfish fed diets with 8%, 12% or 16% RBDPO compared to catfish fed 4% RBDPO or the control diet. Whole-body and muscle lipid content increased when fish were fed with increasing levels of dietary palm oil. Alpha-tocopherol concentrations in muscle and liver tissues increased linearly in response to increasing dietary α-tocopherol originating from RBDPO and CPO. Catfish fed CPO-supplemented diets had about three and five times higher concentrations of α-tocopherol in their muscle and liver tissues, respectively, compared to fish fed RBDPO-supplemented diets at all inclusion levels. It may be concluded that, under the present experimental conditions, the inclusion of at least 8% RBDPO or CPO in African catfish diets improves growth performance, protein retention and fillet vitamin E concentration of this fish.