Caracterización de la actividad enzimática del jugo gástrico de pulpo, Octopus vulgaris y de choco, Sepia officinalis a distintos pH. Digestibilidad in vitro de distintas dietas, con jugo gástrico de pulpo

Abstract

Intensive culture of marine species has been increasing in many countries, such as Japan, Norway, Spain, France, and Greece. Recent research to improve the quality and quantity of aquatic animals production by understanding the process of feeding (ingestion, digestion, and absorption), with emphasis on the digestive enzymatic capabilities is important in order to understand metabolic processes and reduce costs and time on the development of such diets. The impetus to increase knowledge about suitable inert diets to partially or totally replace live feed would reduce this expensive part of the operation, particularly in new potential species, such as the octopus, Octopus vulgaris, and the cuttlefi sh, Sepia offi cinalis, which are two of the most promising cephalopods for large-scale culture. This work is divided into two parts: (1) Enzymatic characterization, by determination of protease activity of the gastric juice at pH ranges from 2 to 12, since this is the major responsible of digestion processes, and (2) In vitro evaluation of several prepared diets, as well as a selection of several natural animal protein sources, by means of a pH-Stat system The results of Part 1 showed that the digestive enzyme activity in total proteases from the gastric juice was higher at pH 7 and 9, therefore being a more alkaline digestion for these species. Total proteases activity was higher at pH 8, while the tripsin activity was higher at pH 7, for both species. For Part 2, the natural diets (natural or liophylized squid, blue whiting and mussel) promoted the highest digestibility, with the highest value being attained with liophylized squid (49%). From the prepared diets, based on raw blue whiting paste, those diets agglutinated with gelatine delivered the highest digestibility. The use of soy protein, as well as heating gelatine as agglutinants, promoted poor digestibility.