이 연구는 우리나라 주요 양식 어종인 넙치를 대상으로 사료 내 단백질, 지질, 탄수화물 원료의 영양소 소화율을 각각 측정하고자 수행되었다.
1. 동물성 사료 원료의 영양소 소화율
본 연구는 넙치 사료의 동물성 원료들의 소화율을 조사하기 위해, 명태분(PM), 고등어분(JMM), 멸치분(AM), 대구분(CM), 정어리+멸치분(SAM), 정어리분(SM), 모래장어분(SEM), 참치분(TM), 육분(MM) 그리고 오징어간분(SLM)을 선정하여 건물, 단백질, 지질, 탄수화물, 에너지 및 필수아미노산의 외견상 소
화율(ADCs)을 측정하였다. CM과 SAM의 건물과 단백질 소화율은 다른 원료들보다 높았고, PM의 단백질 소화율이 가장 낮았다. SAM의 지질 소화율이 가장 높았고, PM의 소화율이 가장 낮았다. SAM과 SEM의 탄수화물 소화율이 가장 높았다. CM, SAM 및 SEM의 에너지 소화율이 높았다. 필수 아미노산
소화율은 단백질 소화율과 비슷하게 나타났다.
2. 식물성 사료 원료의 영양소 소화율
본 연구는 넙치 사료의 식물성 원료들의 소화율을 조사하기 위해, 대두박(SBM), 대두단백농축물(SPC), 대두단백분리(SPI), 채종박(RSM), 완두콩단백질농축물(PPC), 밀글루텐밀(WGM) 그리고 소맥분(WF)를 선정하여 건물, 단백질, 지질, 탄수화물, 에너지 및 필수아미노산의 외견상 소화율(ADCs)을 측정하였다. 건물의 소화율은 SPC와 WGM이 다른 원료들보다 높았고, SBM과 RSM이 가장 낮았다. 단백질 소화율은 SPC, PPC 및 WGM이 가장 높았고, RSM와 WF가 가장 낮았다. 지질과, 탄수화물 및 에너지의 소화율은 SPC의 소화율이 가장 높았다. 필수 아미노산 소화율은 WGM의 소화율이 가장 높았다.
3. 다양한 어분이 함유된 부상사료의 영양소 소화율
본 연구는 넙치 사료에 다양한 어분이 함유된 부상사료의 영양소 소화율을 조사하기 위해 8개의 각기 다른 어분(청어(HM), 멸치(AM), 전갱이(MM), 정어리(SM-A, SM-B), 참치(TM), 명태(PM-A, PM-B))이 함유된 사료를 제작하여 건물, 단백질, 지질, 탄수화물, 에너지 및 필수아미노산의 외견상 소화율(ADCs)을 측정하였다. 건물의 소화율은 MM, SM-A, SM-B 그리고 PM-A가 다른 어분들 보다 높았고, PM-B는 가장 낮았다. 단백질 소화율은 MM, SM-A 및 PM-A가 다른 어분들보다 높았다. 지질의 소화율은 PM-B에서 가장 높았다. 에너지소화율은 MM, SM-A 그리고 PM-A에서 높았다. 필수아미노산 소화율은 MM,
SM-A 및 PM-A에서 높았고, TM에서 낮았다. C18:0 및 C18:3n-3의 소화율은 AM, MM, SM-A 및 PM-A에서 다른 어분들보다 높았고, PM-B에서 낮았다.
4. 다양한 지질원료가 함유된 사료의 영양소 소화율
본 연구는 넙치 사료에 다양한 지질원료가 함유된 사료의 영양소 소화율을 조사하기 위해 오징어간유(SLO), 대두유(SO), 아마인유(LO) 그리고 돈지(LD)을 선정하여 건물, 단백질, 지질, 탄수화물, 에너지 및 필수아미노산의 외견상 소화율(ADCs)을 측정하였다. 건물의 소화율은 SLO 사료에서 높았다. 단백질 소화율은 SLO 사료에서 가장 높았다. 지질의 소화율은 LO와 LD 사료가 SLO와 SO 사료보다 낮았다. 탄수화물 소화율은 SLO, LO 그리고 LD 사료가 SO사료보다 높았다. 에너지 소화율은 SLO 사료에서 높았고, LD 사료가 낮았다.
5. 다양한 탄수화물 원료가 함유된 사료의 영양소 소화율
본 연구는 다양한 탄수화물원료가 함유된 사료의 영양소 소화율을 조사하기 위해, 소맥분(WF), 감자전분(PS), 옥수수전분(CS), 알긴산염(AL), 덱스트린(DEX) 그리고 카복실메틸셀룰로스 (CMC)를 선정하여 건물, 단백질, 지질, 탄수화물, 에너지 및 필수아미노산의 외견상 소화율(ADCs)을 측정하였다. 건물과 에너지의 소화율은 WF, PS, CS 그리고 DEX 사료가 AL과 CMC 사료보다 높았다. 단백질의 소화율은 PS와 CS 사료가 다른 원료들 보다 높았다. 지질과 탄수화물의 소화율은 PS와 DEX 사료가 다른 사료보다 높았다. 이러한 연구 결과들은 양식 사료를 설계하고 제조하는 양식 사료 사업계와 사료 영양 연구자들에게 좋은 정보로 활용 될 수 있을 것으로 기대된다.

1. Apparent digestibility coefficients (ADCs) of selected animal origin feed ingredients for olive flounder (Paralichthys olivaceus)
Apparent digestibility coefficients (ADCs) of dry matter, protein, lipid, nitrogen-free extract (NFE), energy and essential amino acids in selected feed ingredients were determined for olive flounder. Ten test diets were formulated to contain various animal protein sources (pollock fish meal, jack mackerel fish meal, anchovy fish meal, cod fish meal, sardine+Anchovy fish meal, sardine fish meal, sand eel fish meal, tuna meal, meat meal and squid liver meal) designated as PM, JMM, AM, CM, SAM, SM, SEM, TM, MM and SLM, respectively. A reference diet (RF) and test diets with 1.0% chromic oxide (Cr2O3) as an inert indicator that contained 70% reference diet and 30% of the test ingredient were being evaluated. The olive flounder, averaging 150±8.0g, was gathered in 400-l fiberglass tanks with a density of 25 fish in each tank. Fecal samples were obtained from three replicate groups of fish with a fecal collection column which is attached to the fish rearing tank for 4 weeks. Dry matter and crude protein ADCs of CM (95%) and SAM (97%) were significantly higher than the other tested ingredients. Crude protein digestibility of PM (68%) was the lowest among the groups (P<0.05). The highest lipid digestibility was obtained in SAM (97%) and the lowest value was observed in PM (58%). The NFE digestibility coefficients of SAM (94%) and SEM (94%) were significantly higher than those of the other ingredients. Energy ADCs of CM (95%), SAM (93%) and SEM (93%) were significantly higher than the energy ADCs of the other tested ingredients. In general, amino acid availability reflected crude protein digestibility; however, there were major differences in the availability of different amino acids for some of the ingredients. The availability of amino acids in CM and SAM was generally higher than the other animal protein sources and PM was the lowest among the treatments. These results provide more accurate information regarding nutrient and energy utilization of olive flounder and actually will allow ingredient substitutions in practical feed determined on levels of available nutrient requirements.

2. Apparent digestibility coefficients (ADCs) of selected plant feed ingredients for olive flounder (Paralichthys olivaceus)
This study was to determine the apparent digestibility coefficients (ADCs) of soybean meal (SBM), soy protein concentrate (SPC), soy protein isolate (SPI), rapeseed meal (RSM), pea protein concentrate (PPC), wheat gluten meal (WGM) and wheat flour (WF) for olive flounder. A reference diet (RF) and test diets with 1.0% chromic oxide (Cr2O3) as an inert indicator that contained 70% reference diet and 30% of the test ingredient were being evaluated. The olive flounder, averaging 150±8.0g, was gathered in 400-l fiberglass tanks with a density of 25 fish in each tank. Fecal samples were obtained from three replicate groups of fish with a fecal collection column which is attached to the fish rearing tank for 4 weeks. Dry matter ADCs of SPC (75%) and WGM (76%) were higher than the other test ingredients and the dry matter digestibilities of SBM (65%) and RSM (62%) were lower than the other ingredients tested. Protein digestibilities of SPC (80%), PPC (83%) and WGM (84%) in fish were significantly higher than the other test ingredients, and protein digestibilities of RSM (72%) and WF (71%) were lower than the other ingredients tested. The ADCs of lipid, NFE and energy in SPC were the highest among all the dietary treatments. The availability of amino acids in WGM was generally higher than all the other plant feed ingredients tested, and thus had an increased potential to be used as a dietary substitute of fish meal in olive flounder diet. The findings of the current study may assist more efficient and economical formulation of diets using plant feed ingredients for olive flounder.

3. Apparent digestibility coefficients (ADCs) of the extruded pellet diets containing various fish meals as dietary protein sources for olive flounder, Paralichthys olivaceus
Apparent digestibility coefficients (ADCs) of dry matter, crude protein, crude lipid, energy, essential amino acids and fatty acids in selected fish meals were determined for olive flounder (Paralichthys olivaceus). Eight extruded pellet diets were prepared to contain different fish meals (herring fish meal, anchovy fish meal, mackerel fish meal, sardine fish meal-A, sardine fish meal-B, tuna meal, pollock fish meal-A and pollock fish meal-B) designated as HM, AM, MM, SM-A, SM-B, TM, PM-A and PM-B respectively. Chromic oxide (Cr2O3) was used as an inert indicator at a concentration of 0.5% in the diet. Feces were being collected from triplicate groups of olive flounder averaging 151±4.0 g using a fecal collection column which is attached to the fish rearing tank for 4 weeks. Dry matter ADCs of MM, SM-A, SM-B and PM-A diets were higher than all the other dietary groups, and the lowest digestibility of dry matter was observed in PM-B diet. Fish fed the MM, SM-A and PM-A diets showed significantly higher protein ADCs compared to those fed the other experimental diets. Lipid digestibility coefficients of all the selected fish meals were significantly higher than the ADC of PM-B. Energy ADCs of fish fed MM, SM-A and PM-A were significantly higher than the other diets. The availability of essential amino acids in MM, SM-A and PM-A were generally higher than the other fish meals, while TM showed the lowest value among all the fish meals tested. ADCs of (C18:0 and C18:3n-3) fatty acids in AM, MM, SM-A and PM-A were generally higher than those of the other fish meals tested and the lowest value was recorded for PM-B. The findings of this study indicate more accurate information regarding nutrient and energy utilization for olive flounder.

4. Apparent digestibility coefficients (ADCs) of diets containing different oil sources for olive flounder (Paralichthys olivaceus)
Apparent nutrient digestibility coefficients (ADCs) of diets containing different oil sources were determined for olive flounder. Four experimental diets were formulated to contain 10% each of oil sources (squid liver oil, soybean oil, linseed oil and lard) designated as SLO, SO, LO and LD, respectively. Chromic oxide (Cr2O3) was evaluated as an inert indicator at a level of 1.0% in the diet. Feces were collected from triplicate groups of olive flounder averaging 150±8.0 g using a fecal collection column which is attached to the fish rearing tank for 4 weeks. The highest ADC of dry matter observed in SLO (71%) which was significantly higher than that of other dietary lipid sources. Protein digestibility of SLO (84%) was significantly higher than the other tested lipid sources. Lipid ADC of LO and LD diets were significantly lower than that of the SLO and SO diets. The NFE digestibilities of SLO, LO and LD were higher than that of the SO diet. The energy digestibility of SLO was higher than that of the other dietary lipid sources and LD was the lowest among those tested. There were major differences in digestibility of different fatty acids. The results of this study indicated that SLO is highly digestible for olive flounder compared to the other digested lipid sources.

5. Effects of dietary carbohydrate source on apparent digestibility coefficients in olive flounder (Paralichthys olivaceus)
ADCs of dry matter, protein, lipid, nitrogen-free extract and energy in selected carbohydrate sources including wheat flour (WF), α-potato starch (PS), α-corn starch (CS), Na alginate (AL), dextrin (DEX) and carboxymethyl cellulose (CMC) were determined for olive flounder. The olive flounder averaging 151 ± 1.0 g were held in 300 l tanks with a density of 30 fish in each tank. Chromic oxide was used as the inert marker. Feces were collected from the flounder by fecal collector attached to fish rearing tank. Apparent dry matter and energy digestibilities of flounder fed WF, PS, CS and DEX diets were significantly higher compared to fish fed AL and CMC diets. Apparent crude protein digestibility coefficients of flounder fed PS and CS diets were significantly higher compared to those of fish fed AL, DEX and CMC diets. Apparent crude lipid and NFE digestibility coefficients of flounder fed PS and DEX diets were significantly higher than those of fish fed WF, CS, AL and CMC diets. The present findings indicate that α-potato starch and dextrin could be effectively used as dietary carbohydrate energy compared to wheat flour, α-corn starch, Na alginate and carboxymethyl cellulose for olive flounder.