Effects of dietary energy content on the voluntary feed intake and blood parameters of sea bass (Dicentrarchus labrax L.)

Abstract

Energy and protein requirements of sea bass for maximum growth and fasting energy requirements were determined by using three diets containing increasing DE levels and two fish weights.Five hundred and sixteen sea bass were divided in two body weight (BW) classes (A: 67.7 ± 0.85g and B: 128.6 ± 0.88g, mean ± SD live weight) and randomly distributed among 24 tanks. They were fed for 12 weeks on three isoproteic diets characterized by different levels of digestible energy (DE): low energy (LE), 18.6; medium energy (ME), 19.7; and high energy (HE), 22.6 MJ kg-1 dry matter (DM). The entire trial lasted 113 d and was divided into two periods: a feeding trial of 83 d and a fasting trial of 30 d. Specific growth rates decreased in fish fed on the HE diet (P < 0.05), but only in fish weighing 68 g. Voluntary feed intakes and feed conversion ratios were inversely related to dietary energy contents in both weight classes. During the starvation trial, body depletion increased (P<0.05) in fish fed on high-energy diets during the feeding experiment. The gross energy requirements (per day) for maximum growth were 320 and 221 kJ kg-1 BW for fish weighing 68 g and 128 g, respectively. Fasting metabolisms were 60.6 and 54.1 kJ kg–0.83 BW per day for fish weighing 68g and 128g, respectively.It is concluded that growth performance of sea bass appear to be dependent on digestible dietary energy. Gross energy intake, net energy (production) and maintenance requirements of fish were not influenced by dietary treatments.