title: The effect of diet, temperature and intermittent low oxygen on the metabolism of rainbow trout.
abstract: An automated respirometer system was used to measure VO2, protein catabolism as ammonia quotient and the energy budget to evaluate whether the crude protein content of a standard protein (SP) diet (42·5 %) or a high-protein (HP) diet (49·5 %) influences metabolism in rainbow trout under challenging intermittent, low dissolved oxygen concentrations. In total, three temperature phases (12, 16, 20°C) were tested sequentially, each of which were split into two oxygen periods with 5 d of unmanipulated oxygen levels (50-70 %), followed by a 5d manipulated oxygen period (16.00-08.00 hours) with low oxygen (40-50 %) levels. For both diets, catabolic protein usage was lowest at 16°C and was not altered under challenging oxygen conditions. Low night-time oxygen elevated mean daily VO2 by 3-14 % compared with the unmanipulated oxygen period for both diets at all temperatures. The relative change in VO2 and retained energy during the intermittent low oxygen period was smaller for the HP diet compared with the SP diet. However, in absolute terms, the SP diet was superior to the HP diet as the former demonstrated 30-40 % lower protein fuel use rates, higher retained energy (1-4 % digestible energy) and slightly lowered VO2 (0-8 %) over the range of conditions tested. The decrease in retained energy under low oxygen conditions suggests that there is scope to improve the performance of SP diets under challenging conditions; however, this study suggests that simply increasing the dietary protein content is not a remedy, and other strategies need to be explored.
authors.affiliation: 1Forschungs- und Technologiezentrum Westküste,Christian-Albrechts-Universität zu Kiel,Hafentörn 1,25761 Büsum,Germany.
authors.forename: Kevin T
authors.initials: KT
authors.lastname: Stiller
authors.affiliation: 1Forschungs- und Technologiezentrum Westküste,Christian-Albrechts-Universität zu Kiel,Hafentörn 1,25761 Büsum,Germany.
authors.forename: Klaus H
authors.initials: KH
authors.lastname: Vanselow
authors.affiliation: 4Seafood Technologies Group,Plant and Food Research,Nelson 7010,New Zealand.
authors.forename: Damian
authors.initials: D
authors.lastname: Moran
authors.affiliation: 5Skretting Aquaculture Research Centre,Sjøhagen 15,4016 Stavanger,Norway.
authors.forename: Guido
authors.initials: G
authors.lastname: Riesen
authors.affiliation: 5Skretting Aquaculture Research Centre,Sjøhagen 15,4016 Stavanger,Norway.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Koppe
authors.affiliation: 6Georg-August-Universität,Wilhelmsplatz 1,37073 Göttingen,Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Dietz
authors.affiliation: 2Gesellschaft für Marine Aquakultur,Hafentörn 3,25761 Büsum,Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Schulz
mesh_terms: D000818:Animals; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology; D004734:Energy Metabolism / Q000187:drug effects*; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D013696:Temperature
chemical_list: D004044:Dietary Proteins; D010100:Oxygen
keywords:  AQ ammonia quotient;  DO dissolved oxygen;  DOsat
                  DO saturation;  EB energy budget;  EN energy of non-faecal nitrogen;  FCR feed conversion ratio;  HP high protein;  MBW metabolic body weight;  ME metabolisable energy;  MO manipulated oxygen;  RE retained energy;  SDA specific dynamic action;  SGR specific growth rate;  SP standard protein;  TAN total ammonia nitrogen;  TP temperature phase;  UO unmanipulated oxygen; Ammonia quotients; Diurnal hypoxia; Energy budget; Oxygen consumption; Re-circulating respirometer system; Retained energy