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.

Topic: Aquaculture Nutrition and Growth
Subfield: Aquatic Science
Field: Agricultural and Biological Sciences
Domain: Life Sciences