Daily feeding and protein metabolism rhythms in Senegalese sole post-larvae

Fish hatcheries must adapt larval feeding protocols to feeding behavior and metabolism patterns to obtain more efficient feed utilization. Fish larvae exhibit daily ingesting rhythms rather than ingesting food continuously throughout the day. The aim of this study was to determine the daily patterns of feed intake, protein digestibility, protein retention and catabolism in Senegalese sole post-larvae (Solea senegalensis; 33 days post-hatching) using 14C-labeled Artemia protein and incubation in metabolic chambers. Sole post-larvae were fed at 09:00, 15:00, 21:00, 03:00 and 09:00+1 day; and those fed at 09:00, 21:00, 03:00 and 09:00+1 day showed significantly higher feed intake than post-larvae fed at 15:00 h (P=0.000). Digestibility and evacuation rate of ingested protein did not change during the whole cycle (P=0.114); however, post-larvae fed at 21:00 and 03:00 h showed the significantly highest protein retention efficiency and lowest catabolism (P=0.002). Therefore, results confirm the existence of daily rhythmicity in feeding activity and in the utilization of the ingested nutrients in Senegalese sole post-larvae.This work received national funds from Fundação para a Ciência e a Tecnologia (FCT; Portugal) through projects CCMAR/Multi/04326/2013 and SOLEAWIN (310305/FEP/71). It was partially supported by the PROMAR Program with funds from Fundo Regional para a Ciência e Tecnologia (FEDER), and also through the Ministerio de Economía y Competitividad (MINECO; Spain) by project EFISHDIGEST (AGL2014-52888-R) with FEDER/European Region Development Fund (ERDF) contribution granted to M.Y. (Spain). Thanks are also due to European Cooperation in Science and Technology (Cost Action) FA0801 (Larvanet). C.N.-G. was supported by a doctoral fellowship (BES-2012-051956) from Ministerio de Economía y Competitividad (Spain). S.E. acknowledges a FCT investigator grant IF/00482/2014/CP1217/CT0005 funded by Fundação para a Ciência e a Tecnologia (FCT; Portugal) and the European Social Fund under the Operational Programme for the Enhancement of Human Potential.Peer reviewe