Abstract
Optimising mineral nutrition during early life stages is essential for healthy growth and skeletal development in farmed Atlantic salmon (Salmo salar L.). Across three freshwater feeding trials, we investigated the roles of dietary phosphorus (P), calcium (Ca), vitamin K, and vitamin D in regulating growth performance, bone mineralisation, and spinal deformities in juvenile Atlantic salmon. Diets were formulated with either recommended P levels or a 20% P reduction, tested with or without Ca supplementation, and combined with varying vitamin K and D inclusion strategies.
Phosphorus inclusion was consistently identified as the principal factor influencing mineral homeostasis and bone mineralization across all studies. A moderate reduction in dietary P combined with elevated Ca intake led to reduced growth, reduced mineral levels, and a comparatively higher incidence of skeletal deformities. Vitamin K levels demonstrated no impact on growth, with hepatic vitamin K remaining stable. Moreover, vitamin K was insufficient to offset reduced phosphorus in promoting bone mineralization, and increases in vitamin D levels did not yield evident benefits for skeletal health.
These results emphasize the need for precise phosphorus nutrition and balanced Ca:P ratios in freshwater startfeeding diets. They also underline the need to avoid unnecessary calcium supplementation, supporting robust growth, bone health, and more sustainable feed formulations.