Faecal waste production, characteristics and recovery in European seabass (Dicentrarchus labrax) is affected by dietary ingredient composition

Abstract

The quantitative and qualitative characteristics of faecal waste was studied in European seabass (Dicentrarchus labrax) fed diets with high inclusion of different feed ingredients (field peas, PEA; feather meal, FeM; sunflower cake meal, SFM; wheat dried distillers grain with soluble, WDG; corn gluten meal, CGM and soya protein concentrate, SPC), in two different experimental trials, in order to evaluate if different ingredients affect waste production. Each of the test ingredients was partially replaced with the basal mixture used in the control diet (CON). The ingredients were chosen for their varying levels of starch, protein, soluble and insoluble non-starch polysaccharide contents. Fish having an initial body weight of 120 g were used (20 fish/tank in triplicate groups) in both trials and were fed at 1.0% in trial I and 1.5% in trial II of their body weight for 40 days. Apparent digestibility coefficients (ADC) of dry matter (DM), nutrients (protein, fat, carbohydrate, and phosphorus) of the test diets were significantly altered between groups in trial I, with SFM showing the least ADC for DM, carbohydrate and phosphorus; starch ADC was the least in PEA but only DM digestibility and phosphorus availability were different in trial II. The quantity, recovery percentage, physical characteristics, appearance and chemical composition of the faeces were affected by the test ingredients. Carbohydrate fraction of the diet was the most influential in affecting the quantity and chemical composition of faeces produced. Increased inclusion of NSP rich ingredients (WDG, soluble or SFM, insoluble) resulted in higher faecal recovery percentage, despite higher faeces load. Overall, high inclusion of alternate ingredients affected quantitative and qualitative characters of the faecal waste in European seabass, which has implications for environmental sustainability of European seabass aquaculture.