수온대별 배합사료 크기, 공급횟수 및 수분첨가가 넙치의 성장 및 체조성에 미치는 영향

Abstract

ABSTRACT

Experiment Ⅰ- 1 : Effects of extruded pellet size on growth and body composition of juvenile flounder Paralichthys olivaceus reared in the optimum water temperature.

This study was conducted to investigate the effects of extruded pellet size on growth and body composition of juvenile flounder in the optimum water temperature during the summer season. Four isonitrogenous (50% crude protein) experimental diets were design to pellet diets with several size of 3mm, 5mm, 6mm and 7.5mm size. Olive flounder averaging, 15 ± 0.1g (mean ± SD) were randomly distributed in 12 tanks (1.8 ton each). Pellet diets were hand-fed to apparent satiation in three replicate groups (30 fish per group) of fish twice a daily (09:00h, 17:00h) for 6 weeks. Average water temperature was 16.3 ± 2.3℃ during the feeding trial. Final weight, weight gain (WG), feed efficiency ratio (FER) were significantly higher in fish fed 7.5mm size pellet compared with those of fish fed other size diets, whereas the lowest values were observed in fish fed 3mm size pellet (P<0.05). Crude protein content in whole body of fish fed 5mm and 6mm size pellet were significantly higher than that of fish fed other size diets, but not significantly different among dietary treatments (P<0.05). Crude lipid content in whole body of fish fed 6mm size pellet was significantly higher than that of fish fed other size diets (P<0.05). Based on the results of this study, optimum pellet size for growth performance of juvenile Olive flounder (15∼45g) in the optimum water temperature (16.3 ± 2.3℃) could be determined as 11mm.

Experiment Ⅰ- 2 : Effects of extruded pellet size and feeding methods on growth and body composition of grower flounder Paralichthys olivaceus reared in the optimum water temperature.

This study was conducted to evaluate the effects of extruded pellet size and same volume on growth and body composition of commercial scale farm feeding trial grower flounder, reared in the optimum water temperature. Three replicated groups of fish (initial mean weight of (103 ± 3g) were fed to apparent satiation with two different size diet and two different feeding method (A: 9mm-limit feeding, B: 6mm-limit feeding, C: 9mm-full feeding, D: 6mm-full feeding) for eight weeks. At the end of feeding trial, survival rate was not significantly different according to the diet size and feeding method (P>0.05). Final weights of fish fed diet A and C diets were significantly higher (P<0.05) than those of fish fed B and D diet. But final weight of the fish in the top 30% range was the highest in the fish fed C diet among dietary treatments (p<0.05). And the final body weight of the fish in the lower 10% range was the lowest in the fish fed D diet compares with others groups (p<0.05). Feed efficiency in fish fed A diet was significantly higher than those of fish fed other diets (P<0.05). Moisture, crude protein and ash contents of the liver were not significantly different after 8 weeks of feeding in all groups. Content of lipid in liver appeared to be the highest in the fish fed A diet (p<0.05). Based on the results of this study, optimum pellet size for growth performance of grower Olive flounder (103∼264g) in the optimum water temperature (22 ± 7℃) could be determined as 9mm and optimum limited feeding was more efficient than satiation feeding.

Experiment Ⅱ : Effects of extruded pellet size on growth and body composition of grower flounder Paralichthys olivaceus reared in the upper-optimum water temperature.

This study was conducted to investigate the effects of extruded pellet size on growth and body composition of grower flounder in the upper-optimum water temperature. Four isonitrogenous (50% crude protein) experimental diets were design to different size pellet of 6mm, 7.5mm, 9mm and 11mm. Olive flounder, averaging weight, 130 ± 2g (mean ± SD) were randomly distributed in 12 tanks (1.8 ton each). Each pellet diet was hand-fed to apparent satiation in three replicate groups (20 fish per group) twice a daily (09:00h, 17:00h) for 6 weeks. Average water temperature was 22.4 ± 4.5℃ during the feeding trial. At the end of the feeding trial, no significant differences were observed in the survival and feed efficiency between dietary treatments (P>0.05). Final weight gain was the highest in the fish fed the 11mm size diet, whereas the lowest value was observed in the fish fed 6mm size diet (P<0.05). Moisture content in liver of the fish fed 6mm size diet was significantly higher than those of fishes fed other diets, Fish fed the 11mm size diet showed higher lipid content in liver compared with other size diets (P<0.05). Based on the results of this study, optimum pellet size for the growth performance of grower flounder (132∼315g) in the upper-optimum water temperature (22.4 ± 4.5℃) could be determined as 11mm.

Experiment Ⅲ : Effects of extruded pellet size on growth and body composition of commercial scale farm feeding trial young adult flounder Paralichthys olivaceus reared in the sub-optimum water temperature.

This study was conducted to investigate the effects of extruded pellet size on growth and body composition of commercial scale farm feeding trial young adult flounder reared in the sub-optimum water temperature. Four isonitrogenous (50% crude protein) experimental diets were design to different size pellet of 8mm, 11mm, 11mm with water and 15mm size. Olive flounder, averaging weight, 423 ± 2g (mean ± SD) were randomly distributed in 12 tanks (30m2, 15 ton each). Each pellet diet was hand-fed to apparent satiation in three replicate groups (1000 fish per group) of fish twice a daily (08:00h, 16:00h) for 8 weeks. Average water temperature was 13 ± 4℃ during the feeding trial. At the end of the feeding trial, no significant differences were observed in the survival (P>0.05) and final weight among dietary treatments (P<0.05). Weight gain (WG), feed efficiency ratio (FER) were significantly higher in the fish fed 15mm size pellet than those of fish fed other size diets, whereas the lowest value was observed in the fish fed 8mm size pellet (P<0.05). Based on the results of this study, optimum pellet size for growth performance of young adult flounder (421∼546g) in the sub-optimum water temperature (13 ± 4℃) could be determined as 15mm.

Experiment Ⅳ : Effect of feeding frequency and water addition of extruded pellet on growth and body composition of grower flounder Paralichthys olivaceus reared in the optimum water temperature.

This study was conducted to evaluate the effect of feeding frequency and water addition of extruded pellet on growth and body composition of grower flounder reared in the optimum water temperature (22 ± 7℃). Two replicated groups of fish (initial mean weight of 84g) were fed to apparent satiation with five different feeding frequencies and water addition (A: three times per day without water, B: two times per day without water, C: two times per day with water, D: one time in the morning without water, E: one time in the afternoon without water) for three months. Final weight and weight gain (WG) were significantly higher in the fish fed diet A than the fishes in other dietary treatments (P<0.05). Survival rate and feed efficiency ratio (FER) were not significantly different among dietary treatments (P>0.05). Crude protein and lipid contents in muscle, liver and intestine were not significantly affected by the dietary treatments (P>0.05). These data suggested that optimum feeding frequency is three times feeding per day, and addition of water into the pellet diet is not necessary for the growth performance of grower flounder (84∼305g) raising in the optimum water temperature (22 ± 7℃).

Experiment Ⅴ : Effect of feeding frequency and water addition of extruded pellet on growth and body composition of young adult flounder Paralichthys olivaceus reared in water with sub-optimum temperature.

This study was conducted to evaluate the effect of feeding frequency and water addition of extruded pellet on growth and body composition of young adult flounder reared in the sub-optimum water temperature (12 ± 3℃). Two replicated groups of fish averaging 621 ± 15g (mean ± SD) were fed to apparent satiation with four different feeding frequencies and water addition (A: two times per day with water, B: two times per day without water, C: one time per day with water, D: one time day without water) for three months. Final weight, weight gain (WG), feed efficiency ratio (FER) and survival rate were not significantly different among dietary treatments (P>0.05). Crude protein content in dorsal muscle of fish fed diet A was significantly higher than those of fish fed other diets, but was not significantly affected by dietary treatments, except for diet A (P<0.05). Crude lipid content in dorsal muscle of the fish fed diet C was significantly higher than those of fish fed other diets (P<0.05). Intestinal crude protein contents of fish fed diet B, C and D were significantly higher than those of fish fed diet A (P<0.05). Intestinal crude lipid content of fish fed diet B was significantly higher than those of fish fed other diets (P<0.05). Based on the results of this study, the optimum feeding frequency is one time feeding per day for growth performance of young adult flounder (621∼722g) raised in the sub-optimum water temperature (12 ± 3℃).