Understanding the Interaction Effects between Dietary Lipid Content and Rearing Temperature on Growth Performance, Feed Utilization, and Fat Deposition of Sea Bass (Dicentrarchus labrax)

SIMPLE SUMMARY: There is a growing need to use more efficient feed in fish farming. Designing a proper diet could potentially overcome even negative environmental impacts on the growth of farmed fish. It has been repeatedly stated that the change in temperature followed by the change of seasons can significantly affect the growth of fish. The aim of this work is to study the interaction of the diet (specifically the percentage of fat in it) with the change of temperature in the growth performance, feed utilization and fat deposition of Sea Bass (Dicentrarchus labrax). We used two different temperature regimes (starting at 23 °C and then changed to 17 °C and starting at 17 °C and then changed to 23 °C); fed one of the two commercial diets 16.5 and 20% lipids. We observed better growth rate and feed consumption when fish transferred to warmer water, but no diet-temperature interaction was observed. Different temperature regimes did not affect muscle or liver composition but the different fat diet content affected somatic indexes. In both temperature regimes, for a higher feed intake and body weight, a high fat diet is a better practice. ABSTRACT: This study was conducted to elucidate the interaction effects of temperature and dietary lipid levels (2 × 2 factorial experiment) on the growth performance, muscle, and liver composition in adult farmed European sea bass (Dicentrarchus labrax). Two groups of fish (190 g; 60 fish per group) were distributed in 12 tanks in triplicates and kept at two different temperature regimes; one starting at 23 °C and then changed to 17 °C for 61 days, and the other starting at 17 °C and then changed to 23 °C for 39 days. Two commercial diets containing both ~44% crude protein but incorporating different dietary lipid levels, 16.5% (D16) and 20.0% (D20) (dry matter (DM)), were fed to the fish to apparent satiation; the type of diet fed to each fish group remained constant throughout the experiment. Final body weight, weight gain, and specific growth rate were significantly higher for the fish group held at 23 °C compared to the fish group at 17 °C (before the temperature changes), while the dietary fat content did not have any profound effect in both groups. Furthermore, the different temperature regimes did not affect muscle or liver composition, but, on the contrary, dietary lipids affected hepatosomatic, perivisceral fat, and visceral indexes. Feed conversion ratio and specific growth rate were not affected by the dietary lipid level. An interaction of temperature and dietary lipid content was observed in daily feed consumption (DFC) and final body weight (FBW).