A sustainable krill meal enriched with stickwater boosts feed intake, growth performance, and stress resilience in Atlantic salmon (Salmo salar L.) following simulated acute high-temperature delousing

Sammendrag

Acute delousing stress in Atlantic salmon (Salmo salar L.) significantly reduces post-treatment feed intake, impairing growth, health and welfare. Identifying factors, including dietary ingredients, to reduce the stress effects and resume feeding sooner is essential. Stickwater derived from Antarctic krill (Euphausia superba) meal production is an underutilized resource that, when dried with presscake, contributes to a more sustainable krill meal (QSW KM). This study evaluated the effectiveness of dietary QSW KM in mitigating stress from exposure to repeated simulated crowding and acute high-temperature delousing (AHTD) treatments in salmon farming (430 to 960 g body weight). Comparisons were made with diets containing presscake krill meal (QA KM) or fishmeal (FM). Four diets were tested: low fishmeal (LFM; 7.5 % FM), medium fishmeal (MFM; 15 % FM), QSW (7.5 % QSW KM & 7.5 % FM), and QA (7.5 % QA KM & 7.5 % FM). By the end of the trial, fish fed QA and QSW showed higher feed intake and growth compared to FM treatments. Fish plasma cortisol, glucose and lactate values were elevated after repeated AHTD treatments, indicating stress. Cortisol, high density lipoprotein, as well as hypothalamic pomca1 and pomca2 (putative satiety-signals), were elevated in QA, suggesting improved energy metabolism in line with improved growth. Elevated plasma lactate and liver glycogen in QSW indicated greater energy expenditure compared to FM-fed fish. Although QSW had higher feed intake and feed conversion ratio, growth was comparable to the QA treatment. In conclusion, both krill-based diets enhanced stress resilience and post-treatment recovery more effectively than FM-based diets.