Recommendations for dietary level of micro-minerals and vitamin D₃ to Atlantic salmon (Salmo salar) parr and post-smolt when fed low fish meal diets

Abstract

Atlantic salmon (Salmo salar) feeds have changed drastically in their composition from being predominantly marine-based to plant-based. This has altered the dietary supply and availability of micro-nutrients to Atlantic salmon. The impact of graded inclusion levels of a nutrient package (NP) comprising of 25 different micro-nutrients were studied in Atlantic salmon parr in freshwater (Trial 1) and post-smolts in seawater (Trial 2). In brief, the NP was included from 0 to 400%, where 100% corresponded to the recommendation by the National Research Council, 2011. Micro-nutrients, namely Zn, Mn, Se, Cu, Fe, Co, I and vitamin D3 were included in the NP with the objective of (re)evaluating the dietary need to meet the requirement of Atlantic salmon parr and post-smolt, when fed low fish meal, plant ingredient-based diets. Responses in apparent availability coefficient (AAC), whole body and vertebrae mineral concentrations, and retention were analysed. AAC of Cu, Mn, Se and Zn responded in a quadratic fashion with an increase in NP from 0 to 400% in freshwater parr; AAC could not be measured in post-smolt salmon. The whole-body concentration of Zn, Se, Co and I in Atlantic salmon parr were significantly affected by increasing NP inclusion; the same was observed for Zn, Se and Co in post-smolt Atlantic salmon. Vertebrae mineral concentration as the response criterion was non-responsive in parr; whereas, in post-smolt, Co had a linear increase, while Zn and Se showed a non-linear increase upon 0 to 400 NP inclusion. Zinc concentration and activities of alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) in vertebrae indicated increased bone resorption in post-smolt Atlantic salmon; TRAP activity increased linearly with NP inclusion in post-smolt, but not in parr. Significant correlations between Zn and Se were observed in AAC and vertebral concentrations, indicating an interaction in intestinal uptake and vertebral deposition. Overall, Atlantic salmon parr held in freshwater were able to satisfy the requirement for the trace minerals Zn, Mn, Se, Cu, and Fe through supply from 100–150 NP, corresponding to 101–132, 47–63, 0.6–0.8, 12–16 and 150–166 mg kg −1, respectively; for iodine, dietary supply from 150–200 NP, corresponding to 0.7–1.6 mg kg−1, was required. In the seawater, Atlantic salmon post-smolt, in general, required micro-minerals and vitamin D3 levels as supplied through 150–200 NP, corresponding to 140–177, Zn; 61–67, Mn; 0.9–1, Se; 14–16, Cu; and vitamin D3, 0.06–0.09 mg kg −1 to fulfil the requirement, except for Cu which was satisfied at 100–150 NP, equivalent to 13–14 mg kg −1 diet.

Mesopelagic Species and Their Potential Contribution to Food and Feed Security—A Case Study from Norway

“…Currently, Norwegian farmed salmon are fed more than 70% plant feed ingredients on average [80], with similar levels in Chile, Canada and Australia, while Scotland salmon diets contain slightly higher levels of marine feed ingredients [81]. This blue green shift has changed the dietary supply and availability of marine lipid soluble nutrients [82] and micro-minerals [83][84][85]. The potential of using oil or meal from the mesopelagic biomass could be one of the solutions to secure sufficient and nutritious feed for the aquaculture industry.…”

Micronutrient supplementation affects transcriptional and epigenetic regulation of lipid metabolism in a dose-dependent manner

“…The three feeding groups were fed L1, L2, and L3 diets with graded levels of micronutrient supplementation throughout the experiment (Figure 1(a)). L1 contained 100% of the recommended level [12][13][14]27], whereas L2 and L3 respectively contained twice (200%) and four times (400%) of the recommended level (Supplementary Table 1). The inclusion of plant raw materials progressively increased, while marine based ingredients decreased from 23% at smolt to 8% at final harvest (Supplementary Tables 2 & 3), which resembles a current common practice in the farmed salmon industry.…”

“…In addition, plant ingredients often contain anti-nutrient compounds that prevent efficient absorption of micronutrients in fish [11], which may cause potential nutrient deficiencies even though the feed composition satisfies the required level of micronutrients. In this regard, the recommendations for optimal levels of micronutrients has been reevaluated for salmon feed by taking account of plant ingredients along with the nutrient package containing premixed vitamins and minerals [12][13][14][15].…”

“…Key micronutrients associated with growth performance are vitamin B6, vitamin B12 and folate (vitamin B9) [17] that together comprise part of the one-carbon (1C) nutrients [18]. In contrast to other micronutrients, 1C nutrients showed significant influence on growth performance in zebrafish [17] and salmon [12][13][14][15] feeding trials. Moreover, the 1C nutrients are primary components of the 1C metabolism, which influences different developmental stages and conditions, such as embryonic development, cancer, and neurodegenerative diseases [18][19][20].…”

“…In this trial, fish were split into three dietary groups and fed with graded levels of a nutrient package (NP). Based on the recommendation level for Atlantic salmon [12][13][14]27], the NP contains 24 micronutrient…”