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Résumé :
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There is a considerable body of evidence demonstrating that hormones or metabolites involved in feeding, growth and energy partitioning show significant daily fluctuations suggesting that fish are in different physiological states at different times of the day. As such, they should respond differently to food depending on the time of feeding. It has been also demonstrated that the act of feeding periodically induce a pre-prandial locomotor activity. Thus, feeding time might have an influence on the phase or amplitude of some of the endocrine cycles involved in the physiological regulation of feeding. Nevertheless, data pertaining to the entraining effect of feeding time on endocrine cycles are scarce and results are equivocal. Although it is believed that feeding is required for the maintenance of a rhythmic pattern of circulating hormones and metabolites, the evidence for an effect of feeding time on the plasma profiles of hormones and metabolites involved in somatic growth is limited. It is concluded that daily rhythms in feeding activity may reflect adaptive responses to food availability and predators in the wild. It also depends upon endogenous mechanisms, and one might suppose that feeding activity occurs when the fish is physiologically best prepared to use nutrients efficiently. However the examination of plasma hormone profiles may not be particularly suitable for gaining information about the mechanisms involved in the effect of feeding time on growth of fish. Investigation of hormonal receptors, gene expression or enzymatic activity might provide more pertinent information to elucidate how feeding time affects metabolism and nutrient utilisation.
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