치어기 참다랑어 사료 내 효소처리어분의 이용성에 관한 연구

Abstract

In Chapter 2, study was conducted to estimate effects of dietary enzyme treated fish meal (EFM) as a major protein source on growth, feed utilization and digestibility of bluefin tuna Thunnus thynnus. In the first experiment (trial 1), juvenile bluefin tuna (initial body weight 0.68 g) were randomly stocked into two experimental tanks and fed two experimental diets for 15 days. The two diets are EFM based diet (75 %) and sand lance (SL) as a raw fish feed. At the end of feeding trial, weight gain was not significantly different between fish fed EFM or SL. Feed intake was higher in fish fed SL diet than fish fed EFM. Feed conversion ratio was higher in fish fed SL than fish fed EFM. The survival was higher in EFM group than SL group. The pepsin and lipase activities were significantly higher in fish fed SL than fish fed EFM. The contents of omega 3 and 6 of fish carcass were higher in fish fed EFM than fish fed SL. In the second experiment (trial 2), juvenile bluefin tuna were randomly stocked into two experimental tanks and fed two experimental diets for 14 days. The two diets are EFM based diet (75 %) and sardine fish meal based diet (FM) (75 %). At the end of feeding trial, weight gain was higher in fish fed EFM than fish fed SL. Feed intake was higher in fish fed FM than fish fed EFM. Feed conversion ratio was higher in fish fed FM than fish fed EFM. The pepsin activity was higher in fish fed EFM than fish fed FM. Study in the chapter 3 was conducted to estimate optimum dietary DHA oil level and replacement level of EFM by sardine fish meal for juvenile bluefin. The four diets are 1) EFM75 in which 75 % EFM and 4 % DHA oil were applied, 2) EFM60 in which 60 % EFM and 15 % sardine fish meal were included, 3) DHA 2 in which 2 % of DHA oil was included, and 4) SL as a raw fish feed. In a feeding trial, juvenile bluefin tuna (initial body weight 31.0 g) were randomly stocked into four experimental tanks (water capacity: 57 tons) and fed the experimental diets for 13 days. At the end of feeding trial, weight gain was higher in fish fed EFM75 and SL groups than fish fed DHA2 and EFM60 groups. Feed conversion ratio was lower in fish fed EFM75 and DHA2 groups than EFM60 and SL groups. Survival was higher in fish fed the formulated diet groups (EFM75, EFM60 and DHA2) than fish fed SL. The trypsin and amylase activities were higher in fish fed the formulated diets than fish fed SL. Pepsin and lipase activities were significantly higher in fish fed SL than those fed other diets. In Chapter 4, digestibility of the four diets in Chapter 3 were determined. Tuna feces were collected by both methods (cage and dissection). In the cage methods, protein digestibility was higher in fish fed SL than those of other groups, and the lowest protein digestibility was observed in FM75. In the dissection methods, the protein digestibility was higher in EFM75 than those of other groups, and the lowest was observed in EFM60. Protein and dry matter of digestibility were higher in feces collected by cage than feces collected by dissection. In vitro digestibility of pepsin was compared among nine protein sources for screening of the major protein sources in tuna feed. In the protein digestibility, high values were observed in EFM (92 %) followed by wheat gluten (90 %), and low values were observed in sardine fish meal (57 %) followed by poultry meal (55 %) and soybean meal (43 %). In summary, the studies clearly indicate that (1) dietary EFM can effectively increase growth and digestive enzyme activity (2) dietary sardine fish meal can be used up to 10 % in diets and (3) optimum dietary DHA oil level would be approximately 3% in diets for juvenile bluefin tuna. All the results in the studies indicated that EFM is an excellent protein source that can be used for juvenile bulefin tuna.