Evaluation of Fungal Fermented Rapeseed Meal as a Fishmeal Substitute in the Diet of Penaeus vannamei

Abstract

Rapeseed meal (RSM) was fermented using the fungus, Aspergillus niger and was evaluated as a fishmeal substitute in the diet of Penaeus vannamei. A 45-days’ growth trial was carried out using nine iso-nitrogenous and iso-lipidic diets. Raw/fermented RSM was included in experimental diets at the rate of 0 (control), 25, 50, 75 and 100 g/kg by replacing fishmeal (w/w). Results revealed that shrimp fed a control diet had a weight gain of 211.65% and was comparable up to the treatments fed diets containing 25, 50 and 75 g/kg fermented RSM (221.56, 211.77 and 202.85%, respectively). However, the inclusion of >25 g/kg raw RSM tended to decrease (P<0.05) the weight gain. The broken-line model indicated that the maximum inclusion was 64.4 g/kg for fermented RSM. Though feed conversion ratio (1.71-1.94) and apparent protein utilization (21.42-24.93) were not affected due to dietary modifications, numerically better results were observed with fermented RSM compared to the respective level of raw RSM. No significant difference was observed in survival and was in the range of 86.67 to 96.67%. Carcass lipid level was high in shrimp fed with the diets having test ingredients (9.50-10.23 g/kg wet weight) than those fed a control diet (8.83 g/kg). Haemolymph indices have shown significant differences in total protein, glucose, cholesterol and triglycerides between the control and test diets. The present investigation concluded that fermented RSM could replace higher level (64.4 g/kg) of fishmeal in the diet of P. vannamei when compared to their raw counterpart (25g/kg).