Towards optimisation of fish larval nutrition: the effects of new components in microdiet composition and feeding practices on larval digestive physiology

Optimisation towards fish larval nutrition were studied to facilitate the replacement of live feeds (rotifers and Artemia nauplii) as first feed. The first experiment in this thesis evaluated the impact of different dietary treatments on the diurnal digestive tryptic enzyme activity in gilthead sea bream (Sparus aurata) larvae. In order to evaluate optimum feeding time and frequency, several short-term experiments were conducted at different ages with different dietary treatments such as traditionally used live feeds (rotifers and Artemia) and microdiet. The results suggested that no matter what kind of diet was applied, sea bream larvae have a limited digestive capacity at some point in time during the day. The second study investigated the effect of different substances that potentially can enhance the trypsinogen production and secretion in various age stages of sea bass (Dicentrarchus labrax) larvae via tube-feeding method. The results showed an increase in tryptic enzyme activity after injection of phytohaemagglutinin, protein concentration, Calanus meal (Calanus finmarchicus) and the extract of the commercial microdiet MiniPro in sea bass larvae supported the hypothesis that selected substances can trigger the release of trypsinogen at specific developmental stage. The final study of this thesis focused on the potential of a product sourced from freeze-dried Calanus meal as a major component, as well as trypsin and pancreatin as digestive enzyme supplements in microdiet for sea bass larvae. The main goal of this experiment was to compare and evaluate the ontogenetic development of tryptic enzyme activity in larval sea bass fed either live feed, a commercial microdiet or the microdiet containing the Calanus meal as major ingredient. Results suggested that Calanus meal and pancreatin as a mixture of various enzymes and trypsin could effectively replace fish meal in sea bass larvae diets to achieve higher growth, tryptic enzyme activity, and survival rates

Optimierung von Lupinenmehl für die Aquakultur

Lupine aus ökologischen Anbau stellt eine nachhaltige und kostengünstige Alternative zu Fisch- und Sojamehl in Futtermitteln für die Aquakultur dar. Das Projekt "Optimierung von Lupinenmehl für die Aquakultur" (OLA) entwickelte Verfahren zur Steigerung der Verdaulichkeit von Lupinenmehl in Futtermitteln für karnivoren Wolfsbarsch, und analysierte die Vermarktungschancen von Lupine in der Fischfutterindustrie. Ein Hindernis in der Nutzung pflanzlicher Proteinquellen stellen Substanzen dar, sogenannte antinutritive Substanzen, die die Futteraufnahme und Verdauung von Fischen negativ beeinflussen können. Der Projektpartner, das ttz Bremerhaven, entwickelte in diesem Projekt ein enzymatisches Fermentationsverfahren um diese Substanzen im Lupinenmehl zu reduzieren und Verdaulichkeit und Akzeptanz zu fördern. Die Aquakulturforschung am AWI testete das fermentierte Lupinenmehl gegen herkömmliches Lupinenmehl in steigenden Mengen als Ersatz für Fischmehl in Akzeptanz- und Wachstumsversuchen. Diese zeigten, dass ein Futter mit 50% Lupine vergleichbare Wachstumsraten wie Futter aus 65% Fischmehl hervorbringt. Obwohl die Fermentation eine starke Reduktion der Phytinsäure im Lupinenmehl herbeiführte, hatte dies keine Wirkung auf die Wachstumsperformance bei Tieren über 15 g. Bei kleineren Tieren hatte die Fermentation jedoch eine positive Wirkung auf Wachstum. Enzymatische Analysen zeigten eine signifikante Beeinträchtigung der Verdauungsenzyme durch Lupine. In-vitro Analysen mit der pH-Stat Methode zeigten, dass diese durch Fermentation sowie Toasting reduziert wird. Stakeholderanalysen zeigten eine grundsätzliche positive Bewertung von Lupinen aus ökologischen Landbau als sinnvollen Futtermittelinhaltsstoff. Jedoch wurden Schwankungen beim Angebot, Qualität und Zusammensetzung sehr häufig bei größeren Abnehmern als Ausschluss Kriterium wahrgenommen. Insgesamt zeigte das Projekt, dass Lupinenbasierte Futtermittel (mit oder ohne thermische/ enzymatische Behandlung) sehr gut geeignet sind um sämtliche nutritiven Bedürfnisse der karnivorer Wolfsbarsche zu decken. Lupine wird aber sein Potential als Futtermittelinhaltsstoff nur erfüllen, wenn Engpässe in der Wertschöpfungskette durch Sicherung der Produkt-Qualität und Supply-Chain überwunden werden

LUPINE MEAL AS PRIMARY PROTEIN SOURCE IN DIETS FOR EUROPEAN SEA BASS Dicentrarchus labrax

The continuing growth in dietary sourcing for aquaculture organisms means that 70% of all fish meal and 75-90% of fish oils is now consumed by the aquaculture sector, despite research to replace fished resources with plant alternatives (soy bean, canola, and wheat) in aquaculture diets (Jacquet et al.. 2010; FAO 2014). Lupines have considerable potential to replace fish meal in diets for carnivorous fish. Despite the presence of anti-nutritive phytases and non-starch-polysaccharides, lupines can offer good nutritional value, and are sustainable nitrogen-fixing plants suited to cultivation in temperate regions including Europe. While previously studied in formulated diets for salmonids, there is a dearth of knowledge about the effects of lupines at high inclusion levels on other carnivorous fish like European sea bass (Dicentrarchus labrax). This study determined the effects of high inclusion levels of fermented (reduced content of anti-nutritional substances) and untreated lupine kernel meal on growth of commercially important European sea bass. European sea bass (57.5 ± 0.4g) were fed ten isonitrogenous and isocaloric diets containing 65% fishmeal (control diet), 15% soybean meal + 50% fishmeal (commercial control diet), untreated lupine kernel meal and fermented lupine kernel meal at 15, 30, 50 and 65% inclusion (+ 50, 35, 15 and 0% fishmeal respectively) in triplicate tanks. Enzymatic fermentation was carried out in an attempt to reduce content of phytases and non-starch-polysaccharides. Fifty fish per tank were fed for 91 days ad libitum and growth was monitored as total body weight measured at experiment onset and termination. Final mean body weight ranged from 127.9 ± 1.6g to 140.3 ± 4.4g in the groups with 0 to up to 50% lupine kernel meal inclusion, but was significantly lower in the LM65 and FLM65 groups (90.1 ± 3.6, 89.2 ± 10.5g, p < 0.001). No significant differences were observed between fermented and unfermented lupine kernel meal. The same pattern was reflected in the weight gain, specific growth rate and daily feed intake with significantly lower growth and feed intake in both groups including 65% lupine kernel meal. Fish fed diets containing 50% and 65% untreated and fermented lupine meal showed a significantly lower hepato-somatic index (p < 0.001) compared to the group containing less than 30% lupine meal. The final growth parameters mean body weight, weight gain and specific growth rate clearly indicate that lupine can be successfully included at high levels of 50% to the feed without negative effects on growth (thereby replacing 75% of the fishmeal). A complete replacement of fishmeal by lupine led to a reduction of growth by half, which can be only partly explained by a lower feed intake. In Rainbow trout high inclusion level of 50% inclusion level of lupine kernel meal growth was significantly reduced. In the current study, the hepato-somatic index results may indicate negative effects on organ health of the fish at inclusion levels of 50% or higher. Whereas the inclusion level affects growth and health of European sea bass the fermentation of the lupine had no effect and can be eliminated, further reducing production and treatment costs for lupine. Dehulling of the lupine seeds seem to be sufficient to reduce anti-nutritive substances in lupine kernel meal. Given the much lower cost of lupine kernel meal in comparison to fishmeal (ca. 30% of fishmeal cost by weight), significant economic savings can be made. In conclusion, lupines and lupine kernel meal have great potential as a sustainable, locally produced replacement for fishmeal in diets for the carnivorous European sea bass with no negative effects on growth