Introduction
The composition of marine peptide concentrates varies depending mainly on the raw material, the enzyme type, and the degree of hydrolysis. Also, the inclusion rate in the diet is crucial when evaluating general performance of fish fed protein hydrolysates. In this work, we present two trials: 1) evaluation of the hydrolysis degree to improve feed intake and growth performance in gilthead seabream juveniles (Sparus aurata) juveniles and 2) determination of the optimal inclusion level of a peptide concentrate (Pepsea®, Adisseo) selected from trial 1, in the feed for gilthead seabream (Sparus aurata) juveniles.
Material and methods
Trial 1: Gilthead seabream of 10.94±0.12 g average individual body weight were distributed in 24 tanks of a marine RAS held at 21ºC. A group of 30 animals were stocked per tank. Six diets including 23% fish meal were evaluated: a negative control (NC, no peptide concentrate included) and 5 diets including peptide concentrates with different degree of hydrolysis (Subt, D1, D2 (Pepsea®), D3 and Phy). The peptide concentrate was included in the range of 1.5% to 3.1% to supply the same amount of functional protein. Fish were fed manually twice per day to apparent satiation 6 days per week. Trial lasted 10 weeks.
Trial 2: Fingerlings of 45.55±1.37 g average individual body weight were stocked in 15 tanks of a marine RAS. Fish were fed 5 diets with a 20% fish meal inclusion in all of them: a negative control (20FM, no peptide concentrate included), a commercial control (2S, including 2% of a commercial salmon hydrolysate) and 3 diets with different inclusion levels (2.3%, 1.4% and 0.7%) of the peptide concentrate Pepsea® (2.3PF, 1.4PF and 0.7PF). Fish were fed automatically distributing the daily ration during 12 hours per day and adjusting the feeding rate every 2 weeks. Trial lasted 11 weeks.
Results & conclusions
Trial 1: The seabream fed diet D2 (Pepsea®), showed the best performance compared to the fish fed the NC diet and compared to the rest of the diets. Feed intake was 17% (highest value) and SGR and FCR were 21% higher and 30% lower, respectively.
Trial 2: Fish fed diet 0.7PF yielded better results than the diet 20FM, with 4% higher feed intake values and 3% better SGR. Feed intake, SGR and FCR of fish fed diet 0.7PF were comparable to the values obtained with diet S2, indicating that with a lower inclusion rate, results are very similar.
The results from these two trials showed the relevance of the degree of hydrolysis in the performance efficacy of peptide concentrates in fish diets and the importance of selecting the appropriate inclusion rate to obtain a cost-effective application.