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Abstract(s)
Sustainable feeding practices in aquaculture require a higher use of vegetable feedstuffs,
which are naturally rich in carbohydrates. This can raise some constrains to fish species with
carnivorous feeding habits, due to their poor ability to use dietary carbohydrates. This thesis
aimed to explore the potential of nutritional programming as a new strategy to better
understand the mechanisms underlying the impaired utilization of dietary carbohydrates in
fish. The experimental work relied on multiple approaches: a) rearing trials with larvae and
juvenile fish for assessment of zootechnical criteria; b) analysis with radiolabeled tracers to
follow the metabolic flux of nutrients; c) and genomic expression of key metabolic-genes. In
Chapters 2 and 3, we evaluated how the supplementation of egg-yolk with glucose, through
microinjection, could act as a stimulus and permanently alter some metabolic pathways in
zebrafish. Microinjection was proven an efficient technique to alter the nutritional
composition of embryo’s yolk. We saw that the embryonic window for stimulus delivery is
crucial in determining future outcomes. The late embryo stage was found more suitable to
exert a glucidic stimulus compared with incipient stages of embryogenesis, based on
molecular and metabolic analyses that suggested an improved capacity for glucose utilization.
Chapters 4 and 5 aimed the nutritional programming of the carbohydrate-related metabolic
pathways in gilthead seabream. Recurrent hyperglucidic stimuli were delivered at early larval
development using live preys and a glucose-rich diet, demonstrating that nutritional stimuli
can be performed in a marine fish species during sensitive stages of development, without
compromising survival and growth. We found some short-term effects after stimulus delivery,
on gene expression pattern and metabolic utilization of glucose of post-larvae. In contrast,
juvenile fish exposed to the early stimuli showed only few changes on glucose utilization,
namely a higher absorption of dietary starch. This thesis has generated new knowledge on the
triggering effect of early glucidic events upon the regulation of key metabolic processes,
contributing to a better comprehension over the concept of nutritional programming in fish.
Description
Tese de doutoramento, Ciências da Vida, do Mar, da Terra e do Ambiente (Nutrição), Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015
Keywords
Aquacultura Nutrição dos peixes Planeamento Glucose Metabolismo