Optimisation of trace mineral supplementation in diets for Atlantic salmon smolt with reference to holistic fish performance in terms of growth, health, welfare, and potential environmental impacts

Frontiers in Physiology · 8 authors, 4 centres

AI SUMMARY

FIDELITY 100%

POPULATIONAtlantic salmon smolt (initial body weight 215 ± 1.36 g, non-vaccinated)

INTERVENTIONDiets supplemented with organic trace mineral premix (Bioplex Cu, Mn, Zn, Fe and Selplex) at four inclusion levels (1st to 4th supplementation level)

COMPARISONDiets supplemented with inorganic trace mineral premix (sulphates) at the same four inclusion levels

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AGENT 01 · STRUCTURED SUMMARY

TRACE TO SOURCE

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TL;DR

This study compared organic versus inorganic trace mineral supplements (Cu, Fe, Mn, Se, Zn) at four dietary levels in Atlantic salmon smolt. Organic minerals led to higher growth, better selenium retention, improved fillet yield and fatty acid profile (EPA+DHA), and reduced phosphorus excretion. The findings support using lower levels of organic minerals to improve fish performance and reduce environmental impact.

Full summary

3,374 CHARS

**Background:** Modern Atlantic salmon feeds rely heavily on plant ingredients, which can reduce fish performance and health compared to marine-based feeds. Trace minerals (Cu, Fe, Mn, Se, Zn) are essential for numerous physiological processes, but their bioavailability and effects depend on chemical form (organic vs. inorganic) and dietary level. This study aimed to map the physiological implications of supplemental essential trace minerals in Atlantic salmon smolt, focusing on growth, health, welfare, tissue assimilation, and potential environmental impacts.

**Methods:** A 2 × 4 factorial design was used with two mineral sources (organic [OM] vs. inorganic [IM]) and four dietary supplementation levels (1st to 4th). The organic minerals were Bioplex Cu, Mn, Zn, Fe and Selplex (Alltech Inc.); inorganic minerals were sulphates. Target supplementation levels were: Cu 10–25 mg/kg, Fe 348–550 mg/kg, Zn 88–180 mg/kg, Mn 57–100 mg/kg, Se 0.85–1.00 mg/kg. Eight experimental diets were produced by extrusion and fed to triplicate groups of Atlantic salmon smolt (initial weight 215 ± 1.36 g) for 83 days. Fish were subjected to handling stress in weeks 6–8. Samplings included blood chemistry, tissue mineralisation, whole-body fatty acid profile, fillet technical quality, bone strength, skin histology, and midgut transcriptome (microarray). Apparent digestibility coefficients (ADC) and retention efficiency (RE) were calculated using yttrium oxide as an inert marker.

**Key Results:** Fish fed OM showed significantly higher growth rate at weeks 6 and 7 (p < 0.05) and a tendency for higher final body weight (p = 0.087) and total feed intake (p = 0.080) compared to IM. Mineral ADC was generally higher at the lowest supplementation level; Se ADC increased with supplementation in IM but decreased in OM (interaction p < 0.001). Zn ADC was approximately 6% higher in IM (p = 0.033). Phosphorus ADC decreased with increasing IM supplementation but remained constant in OM. Retention efficiency of Se was significantly higher in OM (highest 42.9% in OM1) vs. IM (lowest 13.2% in IM2) (p = 0.041 for interaction). Cu, Fe, Mn, and Zn RE decreased with increasing supplementation level. Whole-body EPA and DHA were significantly higher in OM (EPA p = 0.003; DHA p = 0.026). Omega-6/omega-3 ratio was lower in OM (p < 0.001). Slaughter yield was significantly higher in OM (p < 0.001), and fillet yield tended to be higher (p = 0.084). Bone strength increased with OM level (p < 0.04). Fillet gaping after thawing was lowest at OM4. Blood serum cortisol was significantly lower in OM after first handling stress (p = 0.023). Midgut transcriptome showed coordinated changes in lipid metabolism genes and downregulation of immune genes, stronger in IM (p = 2.1 × 10⁻⁷).

**Clinical Implications:** Organic trace mineral supplementation improves growth, selenium retention, fillet yield, and fatty acid profile (higher EPA+DHA) in Atlantic salmon smolt, while reducing phosphorus excretion and potentially lowering environmental impact. The study recommends lower supplementation levels for organic minerals (Cu 10–15 ppm, Fe ≤348 ppm, Mn 57–71 ppm, Zn 88–119 ppm, Se 0.85 ppm) compared to inorganic (Zn 119–149 ppm, Se 0.9–0.95 ppm). These findings support the use of organic minerals to enhance fish welfare, product quality, and sustainability in salmon aquaculture.

PICO

PPOPULATION

Atlantic salmon smolt (initial body weight 215 ± 1.36 g, non-vaccinated)

IINTERVENTION

Diets supplemented with organic trace mineral premix (Bioplex Cu, Mn, Zn, Fe and Selplex) at four inclusion levels (1st to 4th supplementation level)

OOUTCOME

Growth (SGR, TGC, final body weight), feed intake, FCR, mineral digestibility (ADC), retention efficiency (RE), tissue mineralisation, blood chemistry, whole-body fatty acid profile, fillet yield and quality, bone strength, skin histology, midgut transcriptome

STUDY TYPE

RCT

SPECIALTY

veterinary medicine

SUMMARISED BY

AI pipeline

FIDELITY CHECK

100% · A

ORIGINAL PAPER

PMC10469859

Optimisation of trace mineral supplementation in diets for Atlantic salmon smolt with reference to holistic fish performance in terms of growth, health, welfare, and potential environmental impacts

Frontiers in Physiology

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ABSTRACT

The aquafeed ingredient inventory is ever changing, from marine to plant based, and recently evolving to incorporate increasing amounts of low trophic, side stream and circular economy based raw materials, each one contributing with variable amounts and qualities of macro- and micronutrients. Meeting the micronutrient requirement of farmed fish for healthy and efficient growth under normal and challenging conditions is of paramount importance. In this study we run a trial based on a 2 × 4 factorial design with three replications for each dietary treatment, where Atlantic salmon smolt were fed one of 8 experimental diets supplemented with either organic or inorganic mineral premixes (copper, iron, manganese, selenium, and zinc) at four dietary inclusion levels. We saw a trend for higher growth rate in the organic mineral groups irrespective of the dietary mineral levels. Mineral digestibility was negatively correlated with increasing mineral supplementation levels for all tested minerals but Se which increased with the increasing supplementation in the inorganic and up to the 2nd inclusion level in the organic mineral groups. Increasing mineral supplementation affected retention efficiency of Zn, Mn, Cu and Fe while mineral source affected only the retention of Se which was higher in the organic mineral groups. Moreover, fish obtained higher EPA and DHA in their body and increased slaughter yield in the organic as compared to the inorganic mineral groups and corroborated that trace mineral inclusion levels play a key role on salmon fillet’s technical quality. More effects from different origin and dietary inclusion levels of trace minerals were seen on fillet yield, fillet technical and nutritional quality, bone strength, skin morphology, organ mineralization and midgut transcriptome.

CITATION EXPORT

Marialena Kokkali, Lene Sveen, Thomas Larsson et al.. Optimisation of trace mineral supplementation in diets for Atlantic salmon smolt with reference to holistic fish performance in terms of growth, health, welfare, and potential environmental impacts. Frontiers in Physiology. (2023). https://doi.org/10.3389/fphys.2023.1214987

AUTHORS

8 · 4 CENTRES

Marialena Kokkali, Lene Sveen, Thomas Larsson, Aleksei Krasnov, Alexandros Giakovakis, John Sweetman, Philip Lyons, Katerina Kousoulaki

1 Department of Nutrition and Feed Technology, Nofima, Bergen, Norway
2 Department of Fish Health, Nofima, Ås, Norway
3 Department of Biological Science, University of Bergen, Bergen, Norway
4 Alltech Inc., Meath, Ireland