The Nutritive Value of Wastewater Grown Barley and its Utilization in Fish Feed

The feasibility of using wastewater grown barley plants as a component of fish feed was evaluated. The barley plants were grown in a hydroponics system on wastewater from a recirculating aquaculture facility. The effects of wastewater application rate on plant growth and pollution potential reduction were investigated. At the end of the experiment, the average crop heights and yields were 31.0 and 36.0 cm and 59 and 83 t ha^-1 at wastewater application rates of 690 and 1380 mL compartment^-1 day^-1, respectively. The hydroponics system reduced the TS, COD, NH₄⁺-N, NO₂^--N, NO₃^--N and PO₄ ^-3-P of the aquaculture wastewater by 51.5-52.9, 72.3-72.3, 81.8-82.3, 97.9-98.2, 78.9-79.7 and 84.7-86.3%, respectively. The aquaculture wastewater grown barley met the energy, fat, Ca, Mg, P, Na, S and Mn dietary requirements of aquatic animals. It exceeded the carbohydrate, crude fiber, Cl, K, Cu, Fe, Se and Zn dietary requirements of fish and shellfish. It did not contain sufficient amounts of protein. The aquaculture wastewater grown barley could potential be used as a component in fish feed, but will require supplementation with a high protein source that contains low concentrations of carbohydrate, crude fiber, Cl, K, Cu, Fe, Se and Zn. Common protein sources that could be used for supplementation included fishmeal, bone meal and blood meal.