抄録
Through a series of experiments, it has been demonstrated successfully that an appropriate choice of ingredients is primary for achieving a reduction in phosphorus (P) and nitrogen (N) loading from carp culture. In this final study, four multi-ingredient diets were examined. In addition to the basal ingredients (fish meal 15%, corn gluten meal 8%, defatted soybean meal 10%, blood meal 3-5%), three of the test diets (PF, MM, and SP) contained 6% each of either poultry feather meal, meat meal or soy protein concentrate, respectively, and the fourth diet (PMS) had each of the three aforementioned ingredients includedat 3%. These diets had crude protein <35%, digestible energy >3.5 kcal/g, available P between 0.65 and 0.66% and total P ranging from 1.26 to 1.36%. The diets were fed to juvenile carp during a 12-week feeding trial. The highest growth was obtained for fish fed the MM diet. The absorption and retention rates of P were higher for the PF diet, whereas these values for N did not showtreatment-related differences. The total discharges per ton fish production were estimated to range between 7.8 and 9.2 kg for P and between 39.1 and 40.7 kg for N. These were lower than the figures for Lake Kasumigaura, a main carp culture site, indicating that proper balancing of protein ingredients aids in efficiently lowering emissions from aquaculture.
