Work

Vitamin E Requirement in Practical Feed for Farmed Atlantic Salmon ( Salmo salar ) During Smoltification and Its Long‐Term Impact on Fish Welfare

Year: 2026

Type: article

Abstract: -tocopherol (aTOH) ranging from 38 to 710 mg/kg were tested in duplicate or triplicate tanks stocked with 110 Atlantic salmon (initial weight: 81 ± 2 g), respectively. After 11 weeks, 12 fish were sampled as freshwater smolts (FW-smolts), while the remaining fish were transferred to seawater and subjected to a challenge involving combined hypoxia and temperature stress before being sampled (seawater smolt [SW-smolt]). Additionally, 22 fish from each tank were transferred to a single sea cage and fed a common commercial diet for 5 months to assess the long-term impact of vitamin E nutrition during smoltification on key welfare indicators in post-smolt. No significant effects of dietary aTOH levels on growth performance were observed, but feed intake increased in FW-smolt fed up to 82 mg/kg. A high deposition of aTOH in liver tissue was observed in both FW- and SW-smolt fed more than 400 mg aTOH/kg. Malondialdehyde (MDA) levels in the liver decreased with aTOH supplementation with breakpoints at 457 mg/kg for FW-smolt and 99 mg/kg for SW-smolt, suggesting life-stage-specific differences in oxidative stress reduction. In SW-smolt, muscle astaxanthin levels increased linearly in response to dietary aTOH. Hematocrit and hemoglobin levels were unaffected in FW-smolt but displayed breakpoints in SW-smolt at 367 and 450 mg/kg, respectively. Welfare assessments revealed that fish fed 38 mg/kg during smoltification had a higher incidence of cataracts at the SW-smolt stage and complete vertebral fusion at the post-smolt stage. These findings suggest a minimum dietary aTOH requirement of 82 mg/kg to mitigate welfare issues, while tissue homeostasis, blood marks, and MDA suggest a practical requirement around 367-450 mg/kg.

Source: Aquaculture Nutrition

DOI: 10.1155/anu/8100107