Nutritional programming of gilthead sea bream for better utilisation of low fish meal and fish oil diets

Abstract

Studies in mammals and humans show that dietary influences exerted at critical developmental stages early in life may have long-term consequences on physiological functions in later life. Nutritional programming phenomenon is largely studied in mammalian models for the understanding of diseases such as the metabolic syndrome or diabetes. The functioning of certain metabolic pathways such as fatty acid metabolism in juvenile fish also depends on specific nutritional signals during the critical developmental periods, demonstrating that the concept of metabolic programming also exists in fish. The concept of early-programming raises the interesting possibility of directing specific metabolic pathways or functions in later-stages of the development. For instance, nutritional programming may improve the use of substitutes to fish meal (FM) and fish oil (FO), and hence to promote sustainability in aquaculture by maximizing the capacity of lipid utilization. The studies in this thesis were designed to investigate the potential value of fatty acids as modulators of early nutritional programming and determine the effect of parental feeding with VO diets on offspring performance along life spam, focusing on egg quality, larval and juvenile stages. In addition, selection of the broodstock for their fatty acid desaturase 2 (fads2) expression levels were also investigated. The studies showed that offspring utilization of low FM/FO diets -low n-3 LC-PUFA- diets improved if nutritional clues were supplied during the spawning period. Obtained offspring from brood fish fed different diets showed different expression of lipid metabolism-related genes such as fads2 at the larval stage even when larvae were fed the same commercial protocol and diets. In addition, diets supplied during the spawning period affected some stess-related genes of the offspring in larval satge. Moreover, these metabolic adaptations led to better utilization of low n-3 LC-PUFA diets in the offspring at 6 and 18 months. Thus, nutritionally programmed fish showed better growth and improved feed utilization, particularly if fish also were nutritionally challenged with a low FM and FO diet in later life stages. In following studies, offspring growth was also improved by selection of the broodstock with high fads2 expression. Thus, broodstock selection can also contribute to better utilization of the low FM and FO diets by offspring at juveniles’ stage. Nutritional programming together with broodstock selection showed promising results to improve low FM and FO diet utilization and may contribute the sustainable development of the aquaculture sector.