Abstract
Simple SummaryThe effects of exercise and diet on growth markers were analyzed in gilthead sea bream juveniles. Under voluntary swimming, fish fed with a high-lipid diet showed lower growth, growth hormone (GH) plasma levels, flesh texture, and higher expression of main muscle proteolytic markers than those fed with a high-protein diet. However, under sustained exercise, most of the differences disappeared and fish growth was similar regardless of the diet, suggesting that exercise improves nutrients use allowing a reduction of the dietary protein, which results in an enhanced aquaculture production.The physiological and endocrine benefits of sustained exercise in fish were largely demonstrated, and this work examines how the swimming activity can modify the effects of two diets (high-protein, HP: 54% proteins, 15% lipids; high-energy, HE: 50% proteins, 20% lipids) on different growth performance markers in gilthead sea bream juveniles. After 6 weeks of experimentation, fish under voluntary swimming and fed with HP showed significantly higher circulating growth hormone (GH) levels and plasma GH/insulin-like growth-1 (IGF-1) ratio than fish fed with HE, but under exercise, differences disappeared. The transcriptional profile of the GH-IGFs axis molecules and myogenic regulatory factors in liver and muscle was barely affected by diet and swimming conditions. Under voluntary swimming, fish fed with HE showed significantly increased mRNA levels of capn1, capn2, capn3, capns1a, n3, and ub, decreased gene and protein expression of Ctsl and Mafbx and lower muscle texture than fish fed with HP. When fish were exposed to sustained exercise, diet-induced differences in proteases’ expression and muscle texture almost disappeared. Overall, these results suggest that exercise might be a useful tool to minimize nutrient imbalances and that proteolytic genes could be good markers of the culture conditions and dietary treatments in fish.
Highlights
One of humanity’s greatest challenges is feeding a constantly growing population, in a situation in which the availability of natural resources is limited and respect for ecosystems must be a priority
GHplasma plasma levels and the growth hormone (GH)/insulin-like growth-1 (IGF-1) ratio were significantly higher in fish fed with in comparison to those the GH/insulin-like growth factors (IGFs)-1 ratio were significantly higher in fish fed with high-protein diet (HP) in comparison to those fed inin
Under voluntary swimming, fish fed with high-energy diet (HE) diet showed retarded growth and higher lipid deposition in muscle compared with that of those fed with HP diet, while these differences were not present in the exercised fish
Summary
One of humanity’s greatest challenges is feeding a constantly growing population, in a situation in which the availability of natural resources is limited and respect for ecosystems must be a priority In this context, the aquaculture sector can help face this demand by providing aquatic products like fish, one of the healthiest sources of high-quality protein, fat, vitamins, and oligo elements [1]. There is still a need to develop the sector towards a better sustainability combined with the improvement of fish growth and product quality In this sense, the reduction of dietary protein was a priority in many nutritional studies since it is the most expensive component in aquafeeds, its catabolism is the main source of water nitrogen loading [2,3,4,5], and the ecological impact (overfishing and habitats destruction) that the use of fish components accounts. It was reported that the lower protein/lipid ratio affected growth through unbalanced availability and use of nutrients, especially indicated by changes in key mitochondrial proteins related to energy metabolism; the sustained exercise counteracted most of these alterations
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