| This paper reported the effects of water temperature,food type,ammonia and nitrite concentration on food intake,food digestion,immunological stress,nutrient content in the muscle,growth and survival of the grouper(Epinephelus lanceolatus?× Epinephelus fuscoguttatus ?).The objective is to determine optimum water temperature,optimum food type and safe concentration of ammonia nitrogen and nitrite.The paper is involved in three parts and listed as follows.(1)The effects of water temperature on the feeding growth,superoxide dismutase activity(SOD)and catalase activity(CAT),digestive enzyme activity and biochemical composition of juvenile grouper was investigated to determine optimum water temperature range of the juvenile grouper growth.The water temperatures were set at 17 o C,21 o C,25 o C,29 oC,33oC and 37 oC.The results were feeding rate,specific growth rate and weight growth rate of juvenile grouper significantly increased with increasing water temperature when water temperature ranged from 17 o C to 33 o C(P<0.05).However,feeding rate,specific growth rate and weight growth rate of juvenile grouper decreased with water temperatures increasing from 33 o C to 37 o C.Optimum water temperature range for juvenile grouper was 30.20 o C-31.29 o C by a quadratic regression correlation between feeding rate,specific growth rate,growth rate,feed conversion ratio and water temperature.The water temperature significantly affected superoxide dismutase activity(SOD)and catalase activity(CAT)(P<0.05).Superoxide dismutase activity(SOD)of the grouper reared at water temperatures of 17 oC and 37 oC were higher than those at water temperatures of 21 oC,25o C,29 o C and 33 o C.The correlations between antioxidant enzymes activity and water temperature by quadratic regression equation model showed that activity of antioxidant enzymes was lowest in the range of 25.24oC-26.49 oC.The protease activity of juvenile grouper was significantly affected by water temperature.The protease activity increased firstly and then decreased when water temperature increased from 17 o C to 37 o C.The protease activity of the grouper reared at a 29 oC and 33 oC than those reared at other water temperatures.The pepsin activity reached a peak at 29 o C and the protease activity of intestinal tissue reached a peak at 33 o C.The lipase activity increased firstly and thendecreased when water temperature increased from 17 oC to 37 oC.The lipase activity of the grouper reared at 21 o C was significantly higher than those reared at the other water temperatures.Amylase activity was far less than activity of protease and lipase.The lipase activity increased with the increase of temperature increased firstly and then decreased when water temperature increased from 17 o C to 37 o C.The amylase activity of the grouper reared at 25 o C was significantly higher than those reared at the other water temperatures.The correlations between protease activity and water temperature by quadratic regression equation model showed that the optimum water temperature range for the protease was27.82 o C-31.44 o C.Alkaline phosphatase(AKP)activity in the serum at 17 o C was higher than those reared at other water temperatures.In summary,pearl gentian grouper optimum rearing water temperature is 27-33?.(2)A 9-weeks feeding trial was conducted to evaluate the affect of different food types on the growth performance,digestive enzyme activity,muscle composition and muscle amino acid content of juvenile grouper.The food types included artificial feed(Group A),ice fresh fish(Group B),ice fresh shrimp(Group C),artificial mixed feed and ice fresh fish(Group D),artificial mixed feed and ice fresh shrimp(Group E).The results showed that the weight growth rate and specific growth rate of the Group B were significantly higher than the other groups(P<0.05).The Group A had higher protein efficiency ratio than the other groups.The Group D had lower specific growth rate,weight growth rate and protein efficiency ratio than the Group B,and slight higher than the Group A,C and E.On day 14,the weight growth rate and the specific growth rate of the Group A,D and E were significantly higher than those of the Group B and C.On days 42 and 56,the weight growth rate and the specific growth rate of the Group B were significantly than those of the Group A,D and E(P<0.05).Pepsin activity of the Group B and D were significantly higher than the Group A and E(P<0.05).The lipase activity of the Group B was significantly higher than the other groups.The crude protein content of the Group A and D were significantly higher than the Group B,the crude lipid content of the Group B was significantly higher than the other groups.Delicious amino acids,essential amino acids and amino acid content in the muscle of the Group D were higher than the other groups.A comprehensive analysis suggests an optimum feed protocol for the grouper,where artificial food with balanced nutrient should be provided at early stage,a mixed food of artificial diet and fresh fish at middle stage,and then a mixed food of artificial diet,fresh fish and shrimp at grow-up stage.(3)The acute toxic effects of ammonia and nitrite on the grouper with body weight59.37±7.11 g have investigated indoors.The water temperature,p H values,salinity,anddissolved oxygen were 28.57±1.61 oC,7.7±0.1,28±1 ‰ and 5.5±1.0mg/l,respectively.The results showed that the half lethal concentrations(LC50)and the safe concentrations(SC)of ammonia on the grouper at 24 h,48h,72 h and 96 h were 43.15mg/l,40.16mg/l,37.71mg/l,33.43mg/l and 3.343mg/l,respectively.The half lethal concentrations(LC50)and the safe concentrations(SC)of non-ionic ammonia concentration were 1.599mg/l,1.488mg/l,1.397mg/l,1.239mg/l,and0.1239mg/l,respectively.The half lethal concentrations(LC50)and the safe concentrations(SC)of nitrite were 306.72mg/l,227.09mg/l,131.40mg/l,90.41mg/l,and 9.041mg/l,respectively. |
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