High feeding and growth rates in common octopus ( Octopus vulgaris ) fed formulated feeds with an improved amino acid profile and mixture of binders

Abstract Four semi‐moist formulated feeds were supplied to Octopus vulgaris subadults (664 ± 70 g; 18.4 ± 0.7°C) in two different experiments. In the experiment #1, two diets were prepared with a new mixture of binders (gelatine 150 g kg −1 , starch 100 g kg −1 and gum 50 g kg −1 ). The GEL 15‐Squid and GEL 15‐Hake feeds included 100 g kg −1 freeze‐dried squid ( Todarodes sagittatus ) or hake ( Merluccius sp.) respectively. Both feeds showed low water disintegration rates at 24 h (13.6–15.0% dry weight). The specific feeding rate was higher in animals fed GEL 15‐Hake (2.7% BW  day −1 ), but the growth and feed efficiency were significantly better in animals fed GEL 15‐Squid (1.4% BW  day −1 and 61.2% respectively; P  < 0.05). The proximate composition of the digestive gland, carcass and whole animals was similar. In the experiment #2, the GEL 15‐Squid amino acid profile was improved by replacing 50 g kg −1 gelatine by 50 g kg −1 freeze‐dried squid ( GEL 10‐Squid) or freeze‐dried fish ( GEL 10‐Fish). These feeds showed higher water disintegration rates (31.7–36.3% dry weight). The feeding rates (2.2–2.3% BW  day −1 ), growth (1.5% BW  day −1 ) and feed efficiency were similar for both diets. Total lipids were higher in the digestive gland and whole animals fed GEL 10‐Fish diet ( P  < 0.05). Future effort could be directed towards alternative binders that allow improve amino acid balance with a minimum gelatine content or even supplementation trials including essential amino acids.