Increased dietary protein‐to‐lipid ratio improves survival during naturally occurring pancreas disease in Atlantic salmon, Salmo salar L.

Abstract

This study demonstrated that increased dietary protein‐to‐lipid ratio (P/L‐ratio) improved survival of farmed Atlantic salmon naturally affected by pancreas disease (PD). In addition to diet, body weight (BW) and delousing mortality prior to the PD outbreak also contributed significantly (p < 0.05) to explain the observed variation in PD‐associated mortality. Subsequent to the PD outbreak, large amount of fish failed to grow and caused thin fish with poor condition (runts). At the end of the trial, significantly (p < 0.05) lower amounts of runt fish and increased amount of superior graded fish where detected among fish fed increased P/L‐ratio and within the fish with the largest BWs prior to PD. Diet, BW and delousing mortality contributed significantly (p < 0.05) to explain the variation in the amount of superior graded fish, whereas BW and diet explained the variation in the amount of runt fish. A significant (p < 0.01) negative linear relationship was observed between the amount of superior graded fish and the total mortality, whereas a positive linear relationship was detected between percentage of fillets with melanin and the total mortality. Thus, increased dietary P/L‐ratio seem to reduce the mortality and impaired slaughter quality associated with PD.

Rib abnormalities and their association with focal dark spots in Atlantic salmon fillets

“…The occurrence of fillet-black DS after five months in seawater coincides with Bjørgen et al (2019), who proposed that fillet-red DS are acute focal changes that develop into chronic melanized fillet-black DS (Bjørgen et al, 2015). The prevalence of filletblack DS was 43% on average at harvesting, which is higher than former reports for harvest sized salmon (range 8-33%) (Bjørgen et al, 2019;Dessen et al, 2019;Lutfi et al, 2022;Sissener et al, 2016), though our evaluation method was more sensitive.…”

Increasing dietary levels of the n-3 long-chain PUFA, EPA and DHA, improves the growth, welfare, robustness and fillet quality of Atlantic salmon in sea cages

“…It has been extensively demonstrated that dietary and environmental challenges influence fish health and can ultimately have a massive impact on growth performance [36], particularly when stress and diseases come into play [37]- [39]. In addition, although no significant differences were found in feed intake for the whole feeding trial period, fish fed the 3.5%…”

“…One possible explanation for the differences in growth found at the end of our trial could be related to stress induced by a delousing procedure (August 2018) as well as the onset of a CMS outbreak (September 2018). It has been extensively demonstrated that dietary and environmental challenges influence fish health and can ultimately have a massive impact on growth performance (36) , particularly when stress and diseases come into play (37)(38)(39) . In addition, although no significant differences were found in feed intake for the whole feeding trial period, fish fed the 3•5 % EPA and DHA diet, when compared with the other groups, had a higher SFR and showed a tendency to increased feed intake during the last part of the trial suggesting an improved feed utilisation during a stressful period (delousing and CMS outbreak).…”

Sudden increased mortality in large seemingly healthy farmed Atlantic salmon (Salmo salar L.) was associated with environmental and dietary changes

“…Plasma was separated by centrifugation, stored on dry ice and then sent to the Central Laboratory at the Norwegian University of Life Sciences (Oslo, Norway) for analysis of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (AP) based on the methods described by Tietz (1995). In addition to the mentioned samplings, fish were routinely sampled from all experimental pens at several occasions for analysis of biometric parameters (visceral somatic index referred to as VSI and visceral fat score) and muscle fat content as described by Dessen et al (2018). The specific feeding rate (SFR), condition factor and organ indices were also calculated as described in the mentioned study.…”