In vivo studies of digestion and nutrient assimilation in marine fish larvae

• Published in: Aquaculture 2001-09, Vol.201 (1), p.161-175
• Main Authors: Rønnestad, Ivar, Rojas-Garcı́a, Carlos R, Tonheim, Sigurd K, Conceição, Luis E.C
• Format: Article
• Language: English
• Subjects: Assimilation; Biological and medical sciences; Catabolism; CO 2; Digestion; Fish larvae; Fundamental and applied biological sciences. Psychology; General aspects; Hippoglossus hippoglossus; Marine; Method; Vertebrates: digestive system
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/S0044-8486(01)00595-6

This paper describes a method for quantifying the functionality of the digestive system in fish larvae. The system described can provide data for the gut absorption, oxidation and retention (assimilation) of nutrients. A tube-feeding setup (originally described in Aquaculture 116 (1993) (341–352) using 14C-labelled dietary nutrients formed the basis of a new incubation system. This permitted unabsorbed nutrients evacuated from the gut to be distinguished from molecules originating from catabolism of the absorbed nutrient, both of which are present in the incubation water. The system is based on the release, transfer and entrapment of metabolically produced 14C–CO 2 through manipulation of the water pH. The efficiency of the trap has been validated and tested, and provides 100.0±1.3% (S.D.) recovery. The usefulness of the method is demonstrated in a study in which Atlantic halibut post-larvae (46 days post first feeding) were fed a 14C-labelled protein diet. These data show that this protein has a digestibility of 42% for halibut post-larvae. If oxidation had not been measured through the use of the CO 2 trap, digestibility would have been greatly underestimated (at about 25%).