Antinutritive effects of galactomannan-rich endosperm of Sesbania (Sesbania aculeata) seeds on growth and feed utilization in tilapia, Oreochromis niloticus M A Hossain 1 , U Focken, K Becker Department of Aquaculture Systems and Animal Nutrition, Institute for Animal Production in the Tropics and Subtropics, University of Hohenheim, Stuttgart, Germany Correspondence: Professor Dr K Becker, Department of Aquaculture Systems and Animal Nutrition, Institute for Animal Production in theTropics and Subtropics (480B), University of Hohenheim, Fruwirthstr.12, D-70599 Stuttgart, Germany. E-mail: kbecker@uni-hohenheim.de 1 Permanent address: Department of Aquaculture, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh ^ 2202, Bangladesh Abstract An 8-week feeding trial was conducted using tilapia, Oreochromis niloticus L., in a recirculation system maintained at 2770.2 1C to observe the negative e¡ects of Sesbania endosperm on growth and nutri- ent utilization. Five experimental diets were formu- lated to contain 32% protein, of which ¢shmeal was the major source. Endosperm separated from Sesba- nia seeds was included at levels of 0.0%, 2.9%,5.8%, 8.7% and 11.6% in diets 1 (control), 2, 3, 4 and 5, respectively, equivalent to levels of 0.0%, 9.7%, 19.4%, 29.1% and 38.8%, respectively, of whole Sesba- nia seeds. Each treatment had two replicates, eight ¢sh per replicate, with a mean initial live weight of 5.270.1g. Fish were fed 20g per kg metabolic body weight of ¢sh daily. The body weight gain, metabolic growth rate, feed conversion ratio, protein e⁄ciency ratio, protein productive value and energy retention of ¢sh fed the control and diet 2 were signi¢cantly better ( Po0.05) than those of ¢sh fed the other diets. Physical observation showed that the intestines of the ¢sh fed diets that included endosperm contained loose, viscous and sticky material. Fish fed diets 3, 4 and 5 had a lower proportion of dry matter in their faeces, and lower apparent crude lipid and energy digestibility coe⁄cients compared with ¢sh fed the control diet and diet 2. They also had signi¢- cantly reduced levels of muscle and plasma choles- terol, whole-body crude protein, lipid and gross energy. Keywords: Sesbania endosperm, growth, feed utilization, tilapia Introduction Fishmeal, the conventional protein source in ¢sh feeds, is scarce and expensive, particularly in devel- oping countries, where there is a growing demand for alternative protein sources (Fagbenro 1998). Legume seeds could be potential sources of protein and energy in ¢sh feed owing to their low price and availability. However, the extent to which legume seeds can be used in ¢sh feed is limited due to the pre- sence of antinutritional factors (ANFs), de¢ciencies in some sulphur-containing amino acids and the pre- sence of high levels of non-starch polysaccharides (NSPs). Sesbania, a leguminous seed, has consider- able potential as an ingredient in feeds for animals, including ¢sh. It contains 29^36% protein, 5^6% lipid, 45^47% nitrogen-free extract (NFE) and 19^20 kJ g  1 gross energy (Hossain & Becker 2001). In a recent study, we evaluated the nutritive value of Sesbania aculeata seeds for tilapia and found that only 9.7% of the Sesbania seed meal could be included in the diet without adversely a¡ecting growth or feed utilization (Hossain, Focken & Becker 2002).We as- sumed that the reduction in the growth of tilapia fed diets containing higher levels of Sesbania may be related to the ANFs present in the seeds and to the Aquaculture Research, 2003, 34, 1171^1179 r 2003 Blackwell Publishing Ltd 1171