STUDIES ON THE MINERAL REQUIREMENT IN JUVENILE GRASS CARP(CTENOPHARYNGODON IDELLUS C. V.)

The L16(42×29), L16(44×23)and L8(27)tables of the orthogonal design method were applied to the mineral requirements of juvenile grass carp in three series of feeding experiments. In order to obtain the mineral mixture formula with optimum culture effect, the differentiation tests using three parallel cement tanks as a experiment group were conducted in series 4 and series 5 of the rearing experiments. Average body weight of 10.1 g, 5.6 g, 4.4 g, 12.7 g and 75.8 g were employed in the experiment series 1—5.The test diets consisted of casein, dextrin, peanut oil, cellulose powder, vitamin mixture and mineral mix designed in the proper proportion. The feeding tests were conducted in the 3×2×1 m of cement tanks with slightly running water under condition of the water temperature 27.5—31.0℃, 26.0—30.8℃, 29.0—34.0℃, 24.1—31.5℃ and 11.8—25.5℃ in the sequence of the various series of tests. The results showed that adequate amount of mineral mixture was 9.7% of a dry diet for juvenile grass carp. The mineral elements requires in a diet for juvenile grass carp producing the maximal growth were found to be 32.6—36.7 mg calcium, 22.1—24.8 mg phosphorus, 15.5—17.4 mg sulphur, 4.1—4.6 mg iron, 1.8—2.0 mg magnesium, 0.04—0.05 mg cobalt, 0.02—0.03 mg copper, 0.04—0.05 mg manganese, 0.005—0.006 mg iodine, 0.44—0.50 mg zinc, 25.0—28.3 mg potassium, 7.7—8.7 mg sodium and 20.9—23.5 mg chlorine per 100 g body weight per day. Dietary calcium, phosphorus, sulphur, iron, magnesium, cobalt and copper affected greatly the growth of grass carp fingerlings. The adequate ratio between main dietary elements was found to be approximately Ca/P/S/Fe/Mg= 18/12/9/2/1. The feeding experiments demonstrated the proper amount and ratio of minerals in a diet can remarkably promote growth of juvenile grass carp and dietary mineral deficiency can result in the development of anorexia, poor growth, low PER and a high mortality.The biochemical composition of dorsal muscles, vertebrae and blood from both the grass carp fingerlings fed on mainly grass and fed on test diet containing adequate minerals were shown to be conformity each other.