Effects of different feed processing on the growth and the aquaculture environment of turbot juvenile Scophthalmus maximus

Abstract:

Feed processing technology was a main factor which affects the quality of feed particle and its utilization by cultured animals. In this study, we compared two feed produced with different processing technologies in terms of their physical properties, their effects on the growth of turbot juvenile, and their effects on feed utilization and the aquaculture environment. Two kinds of diets (D1 and D2) were fed to turbot juvenile Scophthalmus maximus with initial weight of 16 g for 64 d. D2 showed significantly higher values than D1 (P<0.05) in the average diameter of feed pellets, the average weight of 100 feed pellets, and the water stability, but also showed significantly lower values regarding the water absorption, the bulk density, and the settling velocity (P<0.05). The weight gain rate, specific growth rate, feed intake rate, and protein efficient rate of turbot juvenile fed with D2 were all significantly higher than the D1 group (P<0.05). The apparent digestibility coefficient (ADC) of dry matter and crude protein of D2 group was also significantly higher than D1 group (P<0.05). However there were no differences in ADCs of crude lipid and total phosphorus between the two groups (P>0.05). The nitrogen and phosphorus levels in the aquarium increased significantly after 18 h feeding. The nitrite nitrogen per liter water produced by one kilogram of D2 fish was significantly higher than that produced by D1 fish (P<0.05); whereas the nitrate nitrogen and the total nitrogen produced by D2 were significantly lower (P<0.05). The labile phosphate and total phosphate produced by D2 group were also significantly lower than those of D1 group (P<0.05). The results suggested that the physical properties of feed pellets, the feed utilization, and the aquaculture environment could be all affected by different processing techniques.