Evaluation of sun-dried water fern, Azolla africana, and duckweed, Spirodela polyrrhiza, in practical diets for Nile tilapia, Oreochromis niloticus, fingerlings.

摘要

Two aquatic plants: water fern, A. africana, and duckweed, S. polyrrhiza, were evaluated as feedstuffs in production diets for Nile tilapia, O. niloticus, fingerlings. 11 diets (30% crude protein) containing fish meal protein substituted at a rate of 5, 10, 20, 30 and 100% for either of the plant ingredients were formulated. A diet without any of the plant ingredients served as the control. Nile tilapia fed diets containing duckweed showed superior growth performance. There were no significant differences (P > 0.05) in growth responses of fish fed either 10% duckweed and 5% water fern dietary inclusion or the control diet. There was a growth depression in fish with increased dietary inclusion of both plants. The most cost-efficient diet was obtained in a diet with 30% duckweed dietary inclusion. Results of this study indicated that duckweed and water fern could be substituted for fish meal protein up to 10 and 5%, respectively, in low-cost diets for Nile tilapia without compromising growth. However, complete replacement of fish meal or soyabean meal by water fern or duckweed decreases growth rates and should not be used in tilapia diets.