Effects of gradual replacement of fish meal with soy meal and supplement phytase enzyme supplement on apparent digestibility coefficient and carcass mineral composition of beluga (Huso huso) juvenile

In order to assess the effect of increasing levels of dietary soybean meal and the effect of phytase enzyme supplement on apparent digestibility coefficient of diet protein, energy and dry matter and also carcass mineral composition of beluga juvenile, seven isonitrogenous and isocaloric diets containing various levels of soybean meal (40% and 70%) as gradual replacement of fish meal (Control diet) and three levels of phytase: zero, 1000 and 2000 IU/kg (not in control diet) were fed to triplicate groups of 10 fish (initial mean weight: 80.65±2.16 g) in each tank. Over an 8-week feeding period, significant differences (P<0.05) were observed on apparent digestibility coefficient and mineral composition between fish fed the experimental diets. The partial replacement of fish meal by soybean meal resulted in significantly decreasing in the apparent digestibility coefficient of diet protein and energy and also in carcass phosphorus and calcium content (P<0.05). On the other hand, the apparent digestibility coefficient of diet dry matter and the carcass magnesium content were not affected by the experimental diets (P>0.05). In addition, supplementation of phytase resulted in significant increase in the apparent digestibility coefficient of diet protein and the carcass phosphorus and calcium content (P<0.05). There were not significant difference among substitute effect, phytase effect and interaction in the apparent digestibility coefficient of diet protein, energy and dry matter and moreover in the carcass magnesium (P>0.05). However substitute effect, phytase effect had significant different in the carcass phosphorus and calcium (P<0.05). According to these results, the replacement of fish meal by soybean meal result in decrease the apparent digestibility coefficient of diet protein and energy and also in phosphorus and calcium content in beluga juvenile carcass. On the other hand, supplementations of phytase results in increase the apparent digestibility coefficient of diet protein and the carcass phosphorus and calcium content.