Antioxidant nutrition in Atlantic salmon (Salmo salar) parr and post-smolt, fed diets with high inclusion of plant ingredients and graded levels of micronutrients and selected amino acids

Abstract

The shift from marine to plant-based ingredients in fish feeds affects the dietary concentrations and bioavailability of micronutrients, amino acids and lipids and consequently warrants a re-evaluation of dietary nutrient recommendations. In the present study, an Atlantic salmon diet high in plant ingredients was supplemented with graded levels of nutrient premix (NP), containing selected amino acids, taurine, cholesterol, vitamins and minerals. This article presents the results on the antioxidant nutrients vitamin C, E and selenium (Se), and effects on tissue redox status. The feed ingredients appeared to contain sufficient levels of vitamin E and Se to cover the requirements to prevent clinical deficiency symptoms. The body levels of α-tocopherol (TOH) in parr and that of Se in parr and post-smolt showed a linear relationship with dietary concentration, while α-TOH in post-smolt seemed to be saturable with a breakpoint near 140 mg kg−1. Ascorbic acid (Asc) concentration in the basal feed was below the expected minimum requirement, but the experimental period was probably too short for the fish to develop visible deficiency symptoms. Asc was saturable in both parr and post-smolt whole body at dietary concentrations of 190 and 63–89 mg kg−1, respectively. Maximum whole body Asc concentration was approximately 40 mg kg−1 in parr and 14 mg kg−1 in post-smolt. Retention ranged from 41 to 10% in parr and from −206 to 12% in post-smolt with increasing NP supplementation. This indicates that the post-smolts had an extraordinarily high consumption of Asc. Analyses of glutathione (GSH) and glutathione disulphide (GSSG) concentrations and the calculated GSH based redox potentials in liver and muscle tissue, indicated only minor effects of diets on redox regulation. However, the post-smolt were more oxidized than the parr. This was supported by the high consumption of Asc and high expression of gpx1 and gpx3 in liver. Based on the present trials, the recommendations for supplementation of vitamin C and E in diets for Atlantic salmon are similar to current practices, e.g. 150 mg kg−1 of α-TOH and 190 mg kg−1 Asc which was the saturating concentration in parr. Higher concentrations than what would prevent clinical deficiency symptoms are necessary to protect fish against incidents of oxidative stress and to improve immune and stress responses. There were no indications that the Se requirement exceeded the current recommendation of 0.3 mg kg−1.

Integrated utilization of microalgae cultured in aquaculture wastewater: wastewater treatment and production of valuable fatty acids and tocopherols

“…Feeding experiments with California Yellowtail (Seriola dorsalis) juveniles indicated that DHA and ARA are critical LC-PUFAs to maximize growth and that supplementing a soybean-oil-based diet with 1.2% EPA, 1.2% DHA, and 0.2% ARA is sufficient to meet LC-PUFA requirements (Rombenso et al 2016), whereas the corresponding values in our cultures were 8.6-11.2%, 5.3-6.4%, and 5.4-7.3%. According to feeding experiments of Atlantic salmon, α-tocopherol supplementation of 150 mg kg −1 in the feed is recommended (Hamre et al 2016). Amounts of αtocopherol in our cultures were 2.7-6-fold higher than the recommended dose.…”

“…Furthermore, the micronutrients with antioxidative properties, such as tocopherols protecting FAs from oxidation, are important feed components (Hamre 2011;Hamre et al 2016;Shahidi and Costa de Camargo 2016). Biologically, the most active tocopherol is α-tocopherol (generally known as vitamin E) (Ortíz et al 2006), which is often present in high concentrations in plant oils (Schwartz et al 2008;Hamre et al 2016). However, it is unstable during feed processing, and storage and, therefore, supplementation of feeds with higher concentrations of α-tocopherol than minimal requirements are recommended (Hamre et al 2016).…”

“…Biologically, the most active tocopherol is α-tocopherol (generally known as vitamin E) (Ortíz et al 2006), which is often present in high concentrations in plant oils (Schwartz et al 2008;Hamre et al 2016). However, it is unstable during feed processing, and storage and, therefore, supplementation of feeds with higher concentrations of α-tocopherol than minimal requirements are recommended (Hamre et al 2016).…”

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.…”

Peer Review #1 of "Atlantic salmon (Salmo salar) require increased dietary levels of B-vitamins when fed diets with high inclusion of plant based ingredients (v0.1)"

“…Data from the same dietary experiments on selected minerals and vitamin A, D and K related to bone metabolism and on vitamin C, E and selenium related to redox regulation are given in Hamre et al (2016).…”