Input management in integrated agriculture-aquaculture systems in Yucatan: Tree spinach leaves as a dietary supplement in tilapia culture

Integrated agricultural-aquaculture (IAA) systems involving tilapia culture have been promoted in Yucatan State, Mexico, as a way of producing fish protein and providing additional economic returns in poor rural areas. System productivity is sub-optimal due to lack of management skills, balanced feed (30% protein-content tilapia feed) shortages and deficient technical assistance. To overcome resource limitations, producers complement balanced feed with the leaves of tree spinach (Cnidoscolus chayamansa), a plant found in Yucatan, other parts of Mexico, Central and South America, Africa, Asia and Oceania. Based on experimental data, a bioeconomic analysis was made to determine (1) the combination of balanced feed and tree spinach leaves which minimizes production costs and (2) the combination which maximizes economic returns. In a limited-resource scenario, a combination of 50% balanced feed at manufacturer-recommended ration plus tree spinach ad libitum reduced feeding costs and increased producer economic returns by 37.9% vs. a complete balanced feed diet, 48.4% vs. a half-complete diet, and 98.3% vs. satiety rations. Use of tree spinach leaves in tilapia diets as a part of IAA systems in Yucatan greatly improved feed management efficiency and the results suggest that this feed input may be used for the same purpose in other regions where it is grown. (C) 2009 Elsevier Ltd. All rights reserved.