Digestibility and Pellet Water Stability Studies on Azolla Meal–Based Diets for Juvenile Black Tiger Shrimp, Penaeus monodon

Abstract

The apparent digestibility coefficients of dry matter (ADMD) and crude protein (APD) and water stability in five isonitrogenous practical diets (40% protein) containing azolla (Azolla pinnata) meal as a replacement for soybean meal were determined with juvenile Penaeus monodon (initial body weight, 0.49±0.03 g) through digestibility and pellet water stability trials. An indirect method using chromic oxide (Cr2O3) as an indicator was employed for the determination of digestibility. The water stability experiment was carried out to study the effects of azolla meal (AM) inclusions as a dietary protein alternative to soybean meal (SBM) on percentage dry matter leaching of the tested diets. Increasing replacement levels of azolla meal with soybean meal as protein source in the diets (0, 25, 50, 75, and 100%) did not significantly affect (P>0.05) on apparent dry matter digestibility (ADMD) and apparent protein digestibility (APD) with a range of 76.277.0% and 79.782.0%, respectively. No significant differences (P>0.05) in pellet water stability during the first 3 hours immersion for all diets (<9.8% feed loss) were also found in the study. However the highest inclusion level of dietary azolla meal (100% replacement) showed a worse water stability than the other diets after 3 hours immersion period. The results indicate that azolla meal–based diets could be digested as efficiently as soybean meal–based diets by juvenile P. monodon and have potential as an alternative plant protein source in shrimp diets.