The sustainable “4 F” for rainbow trout (Oncorhynchus mykiss) feeding: Feedstuffs from the Fish Farmer Farmhouse

In trout production, feed sustainability, together animal welfare, quality of the final product and environmental impact are the main challenges to face for the operators. For the aim, a trial was carried out comparing two different feeds characterized by different dietary ingredient composition: D1 included fish meal and conventional feedstuffs and D2 with co-products deriving from fish processing as main protein and lipid source and vegetable feedstuffs coming from the farmhouse owned by the same fish farmer. 600 young rainbow trout (Oncorhynchus mykiss, mean body weight=48±3g) were reared in 6 tanks resulting in 3 replicates per dietary treatment. The main physico-chemical water parameters were monitored to evaluate effects on the environment. At the end of the 8-week trial, the most important growth performances and quality of the fillet were determined in terms of proximate composition and fatty acid profile. Both the groups reached a suitable final mean body weight (D1=172±35.7g; D2=151.65±34.7g). The feed conversion showed a better rate in D2 (1.03±0.02) compared to D1 (1.3±0.03). Water quality exhibited an improvement of the main chemical parameters with a reduction of total ammonia nitrogen and nitrites in D2 (TAN=0.23 mg/l; NO₂-N=0.08 mg/l). No significant differences were observed in fish fillet quality and fatty acid profile. This study showed that dietary ingredient composition, as co-products deriving from animal processing, together with vegetable feedstuffs from the farmer farmhouse, favourably affected the sustainability of the trout production system.