Growth, feed efficiency and condition of common octopus (Octopus vulgaris) fed on two formulated moist diets

In the present study, the growth, feed efficiency and condition of Octopus vulgaris (0.58 to 1.02 kg; 17 to 21 °C) fed two formulated moist diets based on fish and prawn mixed with alginate (group A) or gelatin (group G) as binders, and a control diet based on a crab diet (group C) are compared. The animals showed a suitable degree of acceptance of both formulated diets, grew and produced faeces, with 100% survival in all groups. The best results were obtained with group C, where the animals showed a specific growth rate, specific feeding rate and feed efficiency of 1.61% BW/day, 4.67% BW/day and 33.95%, respectively. They were followed by the animals of group A (0.71% BW/day, 3.10% BW/day and 22.51%) and group G (0.22% BW/day, 1.31% BW/day and 16.06%). No significant difference was observed between groups C and A with regard to feed efficiency or protein productive value (PPV values of 49.01 and 28.49%, respectively), although differences were significant (P < 0.05) between these groups for lipid productive value (23.65 and 1.59%, respectively). The animals of group C showed the highest digestive gland index and greater lipid content in this organ (15.01%) compared with groups A (6.41%) and G (1.27%), although there were no difference in protein or mineral content. A similar pattern was observed for overall body composition. The results suggest that the differences in growth could have been due to lower feed intake of animals fed either formulated diet and indicates the importance of including taste enhancers. The excellent use of the lipids obtained from the crab emphasises the importance of both the quantity and type of lipid supplied. The stability of these diets in water, their texture, nutritive composition and manufacture are discussed. Other formulated feeds with known nutritional composition could be developed based on the format proposed in this work to improve our knowledge of the nutritional requirements of octopus.