Effects of Pressed and Extruded Foods on Growth Performance and Body Composition of Rainbow Trout (Oncorhynchus mykiss)

Abstract

In order to compare the growth performance and quality of flesh of Oncorhynchus mykiss, with two types of food the pressed and extruded foods, an experimental test was conducted in a fish farm. The comparison of both foods with different formulation and different energy is performed in isoenergetic conditions. Following this study, two plans were formulated: the extruded food with 42% crude protein, 28% fat and 17% carbohydrate while the pressed food with 44.7% Crude Protein, 15% fat and 28.6 carbohydrates with digestible energy of 20.9 Mj and 16.48 Mj. The initial average weight of the trouts was 474 g and the fish were bred in two circular tanks supplied with fresh water in open circuit. Each group was fed twice a day. Within a 60 day-experiment, the final average weight of the extruded food group was 759 g (60.12% weight gain) and 724 g for the pressed food group (52.74 % weight gain). The best conversion rate was obtained with the extruded food with 1.17 v.s 1.56 with a survival rate of respectively 98.85 and 97.72%. The extruded feed resulted in more protein, more fat and less moisture in the fillets. Manufacturing technology and the formulation of both foods have had a major influence on the growth performance and flesh quality of rainbow trout.