Dietary carbohydrate utilization in cod (Gadus morhua): metabolic responses to feeding and fasting

Abstract

Moist diets with increasing amounts of carbohydrate (0.5%, 10% and 21% on a dry weight basis) were each fed to duplicate groups of cod (initial weight 370 g) for 8 weeks, after which all groups were fasted for 4 weeks. Protein energy was high and accounted for more than 70% of the gross energy content in all feeds, and the diets were maintained isocaloric by substituting lipid energy for carbohydrate energy. No indigestible binder was added. Excellent growth and feed conversion were obtained in all groups. After 4 weeks of fasting, fish previously fed diets with either 10% or 21% carbohydrate showed significantly higher weight loss than fish fed the diet without carbohydrate. Liver glycogen reached 10% of liver wet weight in fish fed diets containing 10% or 21% carbohydrate and 5% in fish receiving 0.5% carbohydrate after 8 weeks. Following 4 weeks of fasting, liver glycogen was reduced to similar levels in all fish. Plasma glucose levels 4 h after feeding were higher in fish fed the diets with 10% or 21% carbohydrate and plasma free amino acid levels (FAA) were lower, than in fish fed the diet containing 0.5% carbohydrate. Blood lactate concentrations were unaffected during the first 24 h after feeding. After 4 weeks of food deprivation, the levels were significantly reduced only in the 21% carbohydrate group. A link between glucagon and protein metabolism is suggested because plasma glucagon concentration followed the same pattern as the concentrations of plasma FAA throughout the study. Insulin and glucagon-like peptide (GLP) showed a covariation throughout the experiment. Reduced plasma insulin levels were seen after fasting concomitant with reduction in the levels of FAA and glucose. It is suggested that insulin secretion in cod is affected both by plasma FAA and glucose and that cod meets food deprivation by slowing down metabolism.

Energy dilution with α-cellulose in diets for Atlantic cod (Gadus morhua L.) juveniles — Effects on growth, feed intake, liver size and digestibility of nutrients

“…The market value for cod liver is not as high as the market value for cod muscle, therefore it is desirable that cod use protein for muscle growth and reduce liver growth. Liver size can be reduced by starvation (Hemre et al, 1992;Jobling et al, 1994;Karlsen et al, 1994) and lower feeding frequencies (Dos Santos et al, 1993). To reduce feeding to near starvation will result in reduced muscle growth, which will not be economically for the farmer.…”

“…The same strategy will however not function for cod, as this species stores all surplus energy in the liver. Researchers have shown that a high fat content in cod feed gives enlarged liver Lie et al, 1988;Jobling et al, 1991;Hemre et al, 1992;Jobling et al, 1994;Morais et al, 2001;Rosenlund et al, 2004;Karlsen et al, 2006). Also increased dietary starch seems to increase fat and glycogen deposition in liver (Hemre et al, 1989).…”

Influence Des Conditions D’élevage Sur La Croissance Pondérale Et Les Paramètres Sanguins Utilisés Comme Descripteurs De L’état Physiologique Et Immunitaire De Jeunes Carpes Cyprinus Carpio (Cyprinidae).

“…Les valeurs observées pour l'hématocrite, l'hémoglobine et le nombre de globules rouges sont comparables à celles présentées dans la bibliographie pour différentes espèces de poissons (ROMESTAND, 1983 ;PEREZ et al, 1989 ;HEMRE et al, 1990 ;PEARSON et STEVENS, 1991 ;VELLAS et al, 1994). Des modifications de ces paramètres ont été signalées lors d'un état de stress (SOIVIO et OIKARI, 1976 ;WITTERS et al, 1990 ;WELLS et WEBER, 1991 ;BARTON et IWAMA, 1991) mais de telles variations n'apparaissent pas clairement dans notre étude puisque nous n'avons pas constaté de relation significative avec la glycémie, considérée comme indicateur de stress (COMTE, 1995).…”

“…Nos résultats ne confirment qu'en partie ces observations car la diminution de l'hématocrite et du nombre de globules rouges est amorcée avant la fin de l'été. De nombreux auteurs ont constaté une diminution de ces descripteurs lorsque les poissons étaient à jeun ou dans un état nutritionnel défavorable (HICKEY, 1976 ;MAHAJAN et DHEER, 1983 ;PLUMB et al, 1986 ;HEMRE et al, 1990). Il est donc possible que les ressources naturelles du milieu ne suffisent pas à satisfaire les besoins des poissons, proportionnels à l'augmentation de la température.…”

Haematological and hepatic changes in Catla catla fingerlings in relation to dietary sources and levels of gelatinized carbohydrate

“…Although carnivorous fish have limited capacity to use dietary carbohydrate (Hemre et al 1993, 1995a, Deng et al 2000, improved growth performance with high carbohydrate diets has been demonstrated in rainbow trout, Oncorhynchus mykiss (cf. Kim andKaushik 1992, Grisdale-Helland andHelland 1997), European eel, Anguilla anguilla (cf.…”