Effect of fungal fermentation on apparent digestibility coefficient for dry matter, crude protein and amino acids of various plant protein sources in Penaeus vannamei

Four commercial solvent-extracted oilseed meals/cakes, viz. soybean meal (SBM), groundnut oil cake (GNC), rapeseed meal (RSM) and sunflower oil cake (SFC), were fermented with fungus Aspergillus niger, and its effect on apparent digestibility coefficient (ADC) was studied in Penaeus vannamei. Reference diet and eight experimental diets containing 700 g/kg reference diet and 300 g/kg test ingredient with 5 g/kg chromic oxide were formulated. Each diet was randomly allotted to three tanks containing ten shrimps. Shrimps were adapted to the experimental diets for a week, and faeces were collected using Falcon tube from second week onwards. The ADC of all the ingredients significantly (p<.05) increased with fermentation and the increase being higher in SBM (78.46%-91.71%) for dry matter and in SFC (71.51%-87.02%) for protein. Analysis of variance showed that the ADC of both dry matter and protein significantly (p<.05) differed in treatments (p=<.001) and ingredients (p=<.001). The average ADC of ingredients was ranked as SBM>GNC>RSM>SFC. The most digestible essential amino acid (EAA) in fermented ingredients was methionine in SBM, arginine in GNC, valine in RSM and histidine in SFC. A better improvement in amino acid digestibility was observed in fermented SFC. Results indicated that P.vannamei efficiently digests fermented ingredients compared to unfermented ones.