Responses in rainbow trout (Oncorhynchus mykiss) to increasing dietary doses of lupinine, the main quinolizidine alkaloid found in yellow lupins (Lupinus luteus)

Abstract This experiment investigated the effect of increasing dietary doses of lupinine, the main quinolizidine alkaloid in Lupinus luteus , on feed intake, growth performance, tissue histology and nutritional composition of rainbow trout ( Oncorhynchus mykiss ). Duplicate groups of rainbow trout (initial body weight of 330 g) were fed extruded fish meal based diets containing 0, 50, 75, 100, 250, 500, 1000 and 5000 mg lupinine kg −1 for 60 days. Feed intake and growth were reduced in response to dietary lupinine, best fit by quadratic regression. Based on these results, the practical tolerance level of lupinine, with regard to growth and feed intake, was ≤ 100 mg kg −1 feed. Carcass composition did not vary among treatments. Despite a depletion of glycogen and lipid stores in the hepatocytes, lupinine did not induce any morphological changes in spleen, kidney, heart or intestinal tissues. These results indicate that the lupinine possesses a strong anti-palatability effect, but does not appear to pose short-term health risks for rainbow trout.