Balance trials with African catfish Clarias gariepinus fed phytase-treated soybean meal-based diets |
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| Authors: | JH VAN WEERD KHALAF AARTSEN & TIJSSEN |
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| Institution: | Fish Culture and Fisheries Group, Wageningen Institute of Animal Sciences (WIAS), Wageningen Agricultural University, Wageningen, The Netherlands |
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| Abstract: | Balance trials were conducted with African catfish Clarias gariepinus to assess the effect of phytase treatment of soybean meal-based diets on growth, feed utilization and nutrient budgets. Isocaloric (20–22 kJ g?1) and isonitrogenous (47–50% protein) diets were tested. In a first experiment the control diet (58% fish meal and 18% soybean meal) was compared with two diets containing 6% fish meal and 69% soybean meal, and two diets containing 29% fish meal and 41% soybean meal. One of each of these two diets had been pretreated with phytase (1000 units per kg dry diet). In the second experiment, the control diet (6% fish meal and 69% soybean meal, pretreated with 1000 units phytase kg?1 dry diet) was compared with four diets that were similar in composition but supplemented with increasing amounts of phytase (15, 380, 750, 1000 units kg?1 dry diet). Replacement of fish meal by soybean meal in the first experiment led to a depression in growth rate and feed utilization parameters. Results of both experiments clearly indicated a positive effect of phytase treatment, particularly on phosphorus digestibility and retention, and consequently the phosphorus conversion efficiency and the phosphorus budget. No differences in these parameters were found between addition of equal amounts of phytase by pretreatment or supplementation. |
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| Keywords: | African catfish Clarias gariepinus nutrient budgets phosphorus phytase soybean meal |
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