Performance of formulated diets with different level of lipids and glutamate supplementation in<i>Octopus vulgaris</i>

Abstract

Growth, feed efficiency and proximate and lipid class composition of subadults Octopus vulgaris (788 ± 133 g; 18.5°C) fed formulated diets of low lipid (LL: 8 g kg−1) and high lipid levels (HL: 84 g kg−1) and each one of these with three different levels of glutamate supplementation (0, 5 and 20 g kg−1) were compared. All the animals accepted the diets with a survival of 100%. The addition of glutamate did not stimulate feeding rates in any of the assays (2.48–2.64 and 1.86–2.01%Body weight day−1 for LL and HL, respectively; P > 0.05). The best growth, feed efficiency and protein productive value were observed in the groups fed 5 or 20 g kg−1 glutamate supplementation at both lipid levels, with significant differences for LL diet (P < 0.05). A better feed efficiency was achieved with the HL diet (14.6–27.5% vs. 2.5–19.2% for LL diet). There were no significant differences in the proximate composition of carcass (animal excluding the digestive gland). However, a substantial amount of lipids accumulated in the digestive gland, mainly triglycerides, was detected as a consequence of higher lipid ingestion or glutamate supplementation. It was notable the lower percentages of phosphatidylethanolamine and phosphatidylcholine in the digestive gland of animals with best growth.