Effects ofYucca shidigeraExtract on Water Quality and Fish Growth in Recirculating-Water Aquaculture Systems

Abstract

In livestock industries such as poultry and swine, an extract of the Yucca shidigera plant has shown promise in controlling ammonia buildup in production facilities. In three trials, effects of Y. shidigera extract on ammonia levels and fish growth in recirculating-water aquaculture systems were evaluated. When added to in vitro ammonia solutions, extract concentrations of 0.043% and 0.43% caused a significant (P < 0.05) reduction in ammonia levels after 24 h. The 0.43% concentration also caused significantly (P < 0.05) lower levels of nitrite and higher levels of nitrate. Both concentrations were subsequently found to be toxic to juvenile channel catfish (Ictalurus punctatus). In a feeding trial, fish fed diets containing 1.1-g/kg concentrations of Y. shidigera extract had decreased (P < 0.10) weight gain and increased feed conversion (P < 0.05) compared with fish fed control diet, but there were no significant differences (P > 0.05) in ammonia, nitrite, and dissolved oxygen levels. These results suggest that Y. shidigera could be evaluated as a preconditioning agent for water-recirculating systems and biofillers but should not be used in direct contact with fish.