Nutritional innovations in superior gilthead seabream (Sparus aurata) genotypes: Implications in the utilization of emerging new ingredients through the study of the patterns of secretion of digestive enzymes

Abstract

To promote sustainability and efficiency for aquaculture production, there are two key actions: i) The implementation of novel nutritional strategies with more sustainable raw materials, that aim to reduce the dependence on fishmeal (FM) and fish oil (FO) in the feeds, and ii) the implementation of a successful breeding program addressed to improve fish growth, feed utilization, and health. Different studies performed on salmonids and European sea bass (Dicentrarchus labrax) support the existence of genetic variability for the utilization of plant or non-marine-based diets. Nevertheless, those studies do not consider that the better zootechnical performance obtained in selected fish can be associated with differences in digestive biochemistry. Therefore, the present study aimed to evaluate the changes in the levels of the activities of different digestive enzymes present in two populations of gilthead seabream (Sparus aurata): reference or selected for high growth. Furthermore, the effect of different diets including a variety of protein ingredients partially substituting FM (poultry meal, insect meal, and bacterial single-cell protein) was assessed on the digestive enzyme profile of both fish genotypes, after 90 days of feeding. Higher levels of certain protein-related enzymes (pepsin and chymotrypsin) were found in selected sea bream fish compared with reference fish. Selected fish also revealed higher ADCs for dietary amino acids, irrespective of the diet fed, compared with the reference group. These results, added to the better growth and feed utilization of selected sea bream compared with reference fish, suggest that selected fish are more able to utilize the combination of emergent ingredients for aquafeeds, showing changes in the pattern of digestive enzymes to face the different ingredients in diets, which indicates a higher plasticity of the digestive enzymes to face changes in dietary ingredients. Those changes could be reflecting a compensatory mechanism to improve the digestibility of the ingredient.