Plant meal/oil-based vs. fishmeal/oil-based diet for fillet quality in rainbow trout (Oncorhynchus mykiss): What about a new strategy as a third option?

Final eating quality was evaluated in rainbow trout fed 2 feeds (FF; fishmeal/oil-based, FP; plant meal/oil-based) with 4 feeding strategies: 1) only FF, 2) morning FP, afternoon FF (FF/FP), 3) one day FF, the other day FP (FFFP), and 4) only FP for 150 days. The yield and proximate composition of fillet did not differ between the groups. Neither essential nor nonessential amino acids profile were influenced by the dietary treatments. Fatty acid profile reflected the dietary profile, showing significant changes between the treatments (P < 0.05) with significant reduction in EPA and DHA when plant oils replaced dietary fish oil. Lipid peroxidation level increased with time of storage but decreasing with dietary plant ingredients. Despite the significant changes, TVB-N level was still under acceptable limit (<25 mg/100 g) at the end of the storage. We conclude that replacing dietary fishmeal/oil with plant meal/oil did not impair nutritional value of fillet except decreased n-3 LC-PUFAs such as EPA and DHA. However, these fatty acids were substantially restored when the FF and FP diets were used in turn. On the other hand, decreased lipid peroxidation level showed that shelf-life could be extended with the use of plant ingredients solely or alternatively.