EVALUATION OF DRY CLOVER MEAL AS A FEED PROTEIN RESOURCE IN PRACTICAL DIETS OF JUVENILE GRASS CARP, CTENOPHARYNGODON IDELLA

In order to attain a more economically sustainable, environmentally friendly and viable production, the re-search interest has been directed towards the evaluation and use of unconventional protein sources. This study was conducted to evaluate the suitability of dried clover (Medicago sativa L.) meal as an alternative protein source for grass carp, Ctenopharyngodon idella. A 56d feeding trial was carried out on 6 triplicate groups of 20 fish (8.720.34) g in 250 L aquaria connected to a re-circulating system. Five test diets were formulated to contain clover meal at levels of 2.5%, 5%, 10%, 15% and 20% of the diets or 1.75%, 3.5%, 7.0%, 10.5% and 14.0% of the total plant dietary protein (Diet 1, 2, 3, 4 and 5) respectively and one diet acting as a control which included soybean meal, peanut meal, cottonseed meal and rapeseed meal as protein sources. All diets were isonitrogenous (28.5% crude protein) and isoenergetic (15.92 MJ/kg). No mortality was observed during the whole test period. Fish in diets with 2.5% and 5% dry clover meal (Diet 1 and 2) raised somewhat growth performance and feed effectiveness compared to fish in control. There was no significant dif-ference of growth performance and feed effectiveness between fish in diet of 10% dry clover meal (Diet 3) and fish in control, but fish in diets with 15% and 20% dry clover meal (Diet 4 and 5) significantly depressed growth performance and feed effectiveness compared to control (P0.05). The depression of growth performance and growth parameters could likely be attributed to several factors. Saponins which are found in many of the potential alternative plant-derived feed sources as antinutrients were considered to have a detrimental effect on the fish. A further possible reason for low growth at high dry clover meal inclusion levels might be the increasing of cellulose in diet. Dietary fibre apparently influenced the movement of nutrients along with the gastrointestinal tract and significantly affects nutrient absorption. Fibre could bind nutrients like fat, protein and minerals, and reduced their bioavailability. These results suggested that dry clover meal could be used to 7.8% to adaptable diets and it substituted up to 10% of dietary protein in grass carp without significant reduction in growth.