The composition of the feed for Atlantic salmon in commercial aquaculture is constantly changing over years. The fat levels have increased whereas levels of the omega-3 fatty acids EPA and DHA have decreased. In addition, it has been shown that both the levels of omega-3 fatty acids and fat levels can affect the utilization of minerals.
The purpose of this experiment was to increase the knowledge on how different dietary levels of fat, omega-3 fatty acids, and zinc affects the growth, health, whole body fatty acid retention, and muscle quality of Atlantic salmon in sea cages. The fish grew from an initial weight of 1.5 kg to a final weight of 4.5 kg.
Salmon fed the highest dietary level of EPA + DHA,11% of total fatty acids, had significantly higher final weight than salmon fed 6.5% of these fatty acids. There were no major differences in welfare scores and survival rates between the different diet groups. However, the different diets affected muscle quality. 11% EPA and DHA in the diet improved the red colour in the fillet when compared to the other diet groups, while low dietary Zn resulted in softer texture of the muscle. Higher fatty acid retentions, including EPA retention, were seen in the first growth period in the fall of 2021 than in the second growth period in the spring 2022. The fatty acid composition of tissues largely reflected the fatty acid composition of the feed. The lowest liver fat content was observed in the 11% EPA+DHA group compared to dietary groups fed 6.5% EPA and DHA of total fatty acids.
Overall, these results highlight the importance of the omega-3 fatty acids EPA and DHA and Zn for salmon health and fillet quality.