Marine lipids
D’autres types de formulation d’émulsion doivent donc être testés pour
améliorer les taux d absorption par le naissain. Néanmoins, les stérols se
sont révélés être de bons marqueurs pour la détermination de l’absorption et de la digestion des aliments artificiels lipidiques.
Introduction
To produce seed of consistently good quality and at a competitive price
is an important priority for the mollusc aquaculture industry. Spat
rearing is a critical step. Diet quality often results in variability in
growth and quality with unacceptable overruns for nurseries and oyster
growers.
Sufficient quantities ol microalgae are required for feeding, which are
costly for the hatchery-nursery. A great number of papers on invertebrate nutrition have described the quantitative algal requirements.
However, after supplying the recommended quantity, large variability
are still observed for the subsequent success of spat development. The
biochemical quality of algae is also important to provide essential
nutrients (Utting & Millican, 1995). It is also quite difficult to safely
provide a good phytoplanktonic diet to spat. Emulsions have been
demonstrated to be a successful way to deliver essential fatty acids
(Lane, 1989; Robinson, 1992; Coutteau et al., 1996; Caers et al., 1998,
1999). However, the absorption rates of micronutrients incorporated
in emulsion as well as the relative ingestion of the emulsion versus
algae are still to assess.
The aim of this paper was to estimate ingestion and absorption rates
using sterols as markers. To do this, we fed spat with algae, but lacking
two sterols i.e. stigmasterol and cholesterol that were incorporated as
markers in emulsions. The ingestion-digestion of the emulsion was
followed by measuring the incorporation of the two sterol markers in
oyster spats.
Materials and methods
Emulsion
Two experimental emulsions containing either stigmasterol or cholesterol, 5U of the emulsion dry weight (DW) were prepared by INVE
Technologies NV-SA (Baasrode, Belgium) and contained 50% lipid on
wet weight (WW) basis, water, emulgators, antioxidants, preservatives
and liposoluble vitamins (A, C, D and E, respectively, 0.18, 0.08, 0.013
and 0.32% of WW). The emulsion DW was 70% of the emulsion WW.
Spat culture
Crassostrea gigas juveniles were provided by a French commercial
hatchery. A mixed diet (50:50 on a dry weight basis) of T-lsochrysis
and Tetraselmis suecica was provided daily to spat at a weight specific ration
of 0.75% (algal dry weight per wet weight of spat). The algae of the
124
D’autres types de formulation d’émulsion doivent donc être testés pour
améliorer les taux d absorption par le naissain. Néanmoins, les stérols se
sont révélés être de bons marqueurs pour la détermination de l’absorption et de la digestion des aliments artificiels lipidiques.
Introduction
To produce seed of consistently good quality and at a competitive price
is an important priority for the mollusc aquaculture industry. Spat
rearing is a critical step. Diet quality often results in variability in
growth and quality with unacceptable overruns for nurseries and oyster
growers.
Sufficient quantities ol microalgae are required for feeding, which are
costly for the hatchery-nursery. A great number of papers on invertebrate nutrition have described the quantitative algal requirements.
However, after supplying the recommended quantity, large variability
are still observed for the subsequent success of spat development. The
biochemical quality of algae is also important to provide essential
nutrients (Utting & Millican, 1995). It is also quite difficult to safely
provide a good phytoplanktonic diet to spat. Emulsions have been
demonstrated to be a successful way to deliver essential fatty acids
(Lane, 1989; Robinson, 1992; Coutteau et al., 1996; Caers et al., 1998,
1999). However, the absorption rates of micronutrients incorporated
in emulsion as well as the relative ingestion of the emulsion versus
algae are still to assess.
The aim of this paper was to estimate ingestion and absorption rates
using sterols as markers. To do this, we fed spat with algae, but lacking
two sterols i.e. stigmasterol and cholesterol that were incorporated as
markers in emulsions. The ingestion-digestion of the emulsion was
followed by measuring the incorporation of the two sterol markers in
oyster spats.
Materials and methods
Emulsion
Two experimental emulsions containing either stigmasterol or cholesterol, 5U of the emulsion dry weight (DW) were prepared by INVE
Technologies NV-SA (Baasrode, Belgium) and contained 50% lipid on
wet weight (WW) basis, water, emulgators, antioxidants, preservatives
and liposoluble vitamins (A, C, D and E, respectively, 0.18, 0.08, 0.013
and 0.32% of WW). The emulsion DW was 70% of the emulsion WW.
Spat culture
Crassostrea gigas juveniles were provided by a French commercial
hatchery. A mixed diet (50:50 on a dry weight basis) of T-lsochrysis
and Tetraselmis suecica was provided daily to spat at a weight specific ration
of 0.75% (algal dry weight per wet weight of spat). The algae of the
124