The effects of a microbial phytase derived from Aspergillus niger (Natuphos®, BASF AG Ludwigshafen, Germany) on growth, body mineralization, phosphorus retention and phosphorus excretion were investigated in common carp (Cyprinus carpio L.). The test diet used in this study was based on soybean meal, fishmeal and wheat starch resulting in a total P content of 7.3 g/kg dry matter (DM). This diet was supplemented with two levels of monocalciumphosphate (MCP) and additionally with phytase at levels of 500 and 1000 U/kg. Triplicate groups of fish (10 carp/tank) of mean initial weight of 40 g were fed at a level of 20 g/kg W0.8 d−1 for 9 wk at a water temperature of 23°C. There was enhanced weight gain, crude ash content and P content in whole body with increasing dietary P content and phytase supplementation, respectively. The P gain was about 4 g/kg gain when P supply was adequate. Supplementation with phytase improved utilization of native plant P and reduced the P excretion/kg gain significantly by 30% compared with MCP-supplemented diets. This effect of the phytase was confirmed by measurements of the total P digestibility.

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Apparent digestibilities and growth experiments with tilapia (Oveochvornis niloticus)fed soybean meal, cottonseed meal and sunflower seed meal Summary Apparent digestibility and growth experiments with three oil seed by-products, soybean meal, cottonseed meal, and sunflower seed meal. werc conducted using tilapia (Oreucl~romis niloticus) with an initial average body weight of 93 f 5 g and 64 k 1 g, respectively. The diets were formulated on an isonitrogeneous and isoenergetic basis. During the experimental period the fish were fed 1% and 1.5% of their metabolic body weight (kg' *) daily in the digestibility experiment and the growth experiment. respectively. Waler temperature was maintained at 26.5 2 I T . Apparent digestibilities of the components and the diets were determined using an indirect method, i.c. with HCI-insoluble ash as an indicator. Faeces collection was carried out using a sedimentation technique.Results of the apparent digestibilities showed that the crude protein, crude fat, as well as the gross energy digestibilities of soybean meal (93.0%, 94.6%, and 77.2%, respectively), were better than those of cottonseed meal (79.4%, 83.2%, and 57.9%, respectively) and sunflower seed meal (89.8%,, 82.9%, and 49.3%. respectively). With the exception of the crude protein digestibility, nutrient and gross energy digestibilities of the cottonseed meal were found to be better than that of sunflower seed meal.Growth experiment results indicated that soybean meal diet groups had inferior growth performance and feed conversion in comparison to the fishmeal control diet or the other test diets at an inclusion level of 32% of the digestible protein. Fish fed cottonseed meal diet and sunflower seed tneal diet showed a relatively better, but not significantly different performance than did the fishmeal control diet. Supplementation diets with lysine and methionine did not enhance fish performance.