Improving production efficiency of farmed Atlantic salmon (Salmo salar L.) by isoenergetic diets with increased dietary protein-to-lipid ratio

Abstract

The effects of isoenergetic diets with high (HP) and low (LP) protein‐to‐lipid ratios on feeding rate (SFR), feed conversion (FCR), growth (TGC) and relative‐ and absolute nutrient retention were investigated using both whole‐body weight (BW) and carcass weight (CW) to assess the production efficiency. Three different feeding trials in seawater were conducted: two large‐scale trials with yearling smolt (S1) and under‐yearling smolt (S0) and one small‐scale with S1 smolt. The initial body weights in the trials were 105, 319 and 978 g, respectively, and the fish were fed and monitored until they reached harvest weights. In all three trials, the dietary HP group attained significantly higher (p < .05) CW at harvest based on fish with equal BW. Also, fish fed the HP diets significantly improved FCR (p < .05) when based on CW. In the small‐scale trial, fish fed HP diet, especially during late autumn and spring, significantly (p < .001) improved FCRBW and FCRCW. Improved FCR coincided with significantly higher (p < .05) relative energy retention in the dietary HP group. In all three trials, the HP groups had significantly higher (p < .05) TGC with regard to both BW and CW. Taken together, the present studies indicate that growth performance and feed utilization in modern salmon farming has the potential to be further improved by increasing the dietary protein‐to‐lipid ratio. In addition, dietary influence is more precisely assessed when using carcass as the weight denominator when analysing feed utilization and growth performance.

The impact of dietary protein: lipid ratio on growth performance, fatty acid metabolism, product quality and waste output in Atlantic salmon (Salmo salar)

“…Previous research has led to the widespread implementation of nutritional strategies aiming to spare protein for growth (Karalazos et al 2011a;Weihe et al 2018), minimise nitrogenous waste (Bendiksen et al 2011; and efficiently incorporate health promoting fatty acids into the fillet tissue (Francis & Turchini 2017). Previous research suggests an increased dietary protein : lipid ratio may affect the n-3 LC PUFA sparing capacity and the growth performance of Atlantic salmon (Francis & Turchini 2017;Weihe et al 2018). On the other hand, reductions in nitrogenous waste outputs are achievable through a decreased dietary protein : lipid ratio.…”

“…However, to date results have been inconclusive and further investigation has been suggested (Francis & Turchini 2017). Despite this, an increase in the dietary protein : lipid ratio has been shown to improve the food conversion ratio and thermal growth coefficient in farm reared Atlantic salmon (Weihe et al 2018).…”

Genetic effects of fatty acid composition in muscle of Atlantic salmon

“…Visceral fat content is part of the existing breeding programs and can be dealt with as for other negatively correlated traits by using selection index theory [ 56 ]. In addition, optimizing the protein-to-lipid ratio of the feed can significantly reduce visceral lipid deposition in Atlantic salmon [ 57 , 58 ]. Hence, combining selection and feeding management could prevent increased amounts of visceral fat while selecting for DHA or DHA:ALA ratio.…”

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

“…Regarding growth, the observation of somewhat improved growth within the test group prior to the mortality, may also indicate a dietary effect alone without influence of the disease. Accordingly, diets with increased protein‐to‐lipid ratio compared to current commercial practices, have previously been shown to promote good growth and improve feed utilization in large and small scale experiments carried out in the Faroes Island and Mid‐Norway, respectively (Weihe et al., ).…”