To address the shortage of cheap and sustainable feed-protein ingredient for aquaculture, this study developed Gracilariopsis heteroclada protein concentrate (GHPC) and evaluated its nutritional value as a replacement to soybean meal protein in the diet of black tiger shrimp, Penaeus monodon. Five isonitrogenous and isolipidic diets were formulated replacing soybean meal protein at 0% (control), 12.5%, 25%, 50% and 75%.
Results showed that the developed GHPC has a protein, lipid, fiber and carbohydrate content of 31.11±0.12%, 1.57±0.61%, 1.87±0.31% and 24.99±0.33%, respectively. The nutritional value of GHPC was found high, exhibiting an ingredient digestibility index of 91.84 ± 0.06% and Essential Amino Acid Index (EAAI) of 0.996. Feeding trial results revealed that the overall growth performance, feed assimilation efficiency and biochemical composition of the shrimp fed with the 50% GHPC diet were similar to the control group fed with full soybean meal based-diet (Table 1). The high acceptability of this feed ingredient to P. monodon is attributed to its high digestibility and adequate content of essential amino acids. However, shrimps fed with replacement levels beyond 50% exhibited significant growth depression that might be due to the presence of antinutritional compounds as observed with the reduction of digestive enzyme activities (Figure 1) and histomorphological changes (B-cell enlargement) (Figure 2).
Collectively, the findings suggest that GHPC has high nutritional value and could be used as a plant protein ingredient in the diet of P. monodon. Utilization of GHPC is a sustainable approach to meet the growing requirements of feed-proteins in the expansion of P. monodon aquaculture.