Utilization of waste-grown algae for feeding freshwater shrimps

The purpose of this study was to investigate the possibility of using waste-grown algae as feeding materials for a freshwater shrimp (Macrobrachium hainanense). Chlorella pyrenoidosa cultured in 1% aqueous extracts of soybean waste and refuse compost waste materials were used to feed the shrimp. Five experimental groups were designed: (1) 100% commercial fish food (control group); (2) 50% algal product from soybean waste extract with 50% commercial fish food; (3) 100% algal product harvested from soybean extract; (4) 50% algal product from refuse compost extract with 50% commercial fish food; and (5) 100% algal product from refuse compost extract. After a feeding trial of 20 days, the contents of protein, lipid and soluble carbohydrates of the muscle of shrimps were analysed. The nutrient contents (protein, lipid and soluble carbohydrates) of different feeds were also measured. It was found that shrimps fed with waste-grown algae seemed to maintain a similar nutrient level as the control group. Measurements of heavy metals (Cu, Zn, Mn, Pb) in the culture media, algae, commercial fish food, muscles, and cephalothorax and exoskeletons of shrimps were conducted. It was found that the algal product harvested from the refuse compost extract contained a higher metal content. The metals were mostly incorporated in the cephalothorax and exoskeleton of waste-grown shrimps.