|Abstract: ||石斑魚目前為世界性的高經濟魚種，尤其在亞洲地區仍供不應 求。魚類對於飼料中不同原料的消化率會因魚種不同而有明顯的差 異。了解石斑魚對於原料的消化率，有助於配製飼料配方以降低飼料 成本。 長期以來消化率的研究對於糞便收集的方式一直爭論不休，體內 收集及體外收集各有利弊，因此我們先了解點帶石斑一天中的排糞高 峰期，並針對不同的糞便收集方法(濾網、擠壓)測定消化率的差異， 接著比較以濾網收集時糞便滯留水中時間長短(1、2、3、6 小時)所造成的影響，而後才測定常使用的水產飼料原料消化利用率。 石斑魚飼養於兩個各設置有三個箱網的兩噸FRP 桶中，每個箱 網放置56 尾試驗魚，魚體大小約210±50 克，並加裝有循環水過濾系 統。試驗時所收集的糞便以日期區隔成前中後三等份，平均取樣混合 成三重複進行分析。測試飼料以70％的參考飼料及30％的待測試原 料配製而成，並於飼料中加入 0.5%三氧化二鉻做為標示劑。 試驗一：以擠壓及濾網(每小時收集)法進行糞便的收集。結果顯 示， 擠壓法的消化率數值偏低， 兩者之間的差異約介於 0.36%~3.07%。濾網收集法隨著糞便滯留水中時間延長營養物溶失增 加。以濾網收集糞便與擠壓法收集糞便的消化率差異在蛋白質及無氮 抽出物較明顯，推測可能是由於擠壓法收集糞便時殘留未消化的營養 成分或糞便溶失造成，但因其差異小於4%且考慮收集量的時效性， 濾網是較省時且易執行的一種選擇。 試驗二：以濾網每小時收集糞便加以分析，測定熟化澱粉、麵粉、小麥筋蛋白、玉米筋蛋白、紅魚粉、白魚粉、烏賊粉、去脂大豆粉及全脂乾爆大豆粉共9 種不同原料的各成份表觀消化率。結果顯示，點帶石斑的原料蛋白質消化率約介於87.96%~101.87%，脂質消化率則介於85.00%~96.71%，因此蛋白質及脂質方面無論是植物性原料或動物性原料都可良好的利用；點帶石斑對於原料中所含無氮抽出物消化率不佳，不過對於熟化澱粉卻有良好的消化率，因此澱粉的熟化作用可增加石斑魚的利用。能量消化率則因原料無氮抽出物含量的上升造成負影響。本試驗顯示就消化率而言植物性蛋白可做為石斑魚飼料中的蛋白質替代來源。而澱粉方面必需經過熟化處理，才能確保高消化率。|
Abstract Nowadays, grouper (Epinephelus coioides.) is one of the most economical fish throughout the world. Especially in Asia, its supply is unable to meet the demand. An understanding the digestibility of ingredients for grouper is very helpful in diet formulation,and thus to make the diet cost-effective. Digestibility of feed ingredients is based on fish species. For a long time, digestibility study have had a lot of methods for collecting faeces, for example: dissection, stripping, anal suction, continuous filtration and netting. However, everyone of the aforementioned methods still have some drawback. In the present study, we use two different methods for faeces collection (settling in net and strpping) in order to compare its effect on the digestibility. The settlement period (1、2、3、6 hours) of netting collected faeces was also compared, and finally the common feed ingredients for grouper’s feedstuff was evaluated. For all the experiments, grouper was cultured in two FRP tanks, each one having three cages and 56 fish (initial weight=210±50g). In every tank a recirculation system was setup in order to maintain proper water quality parameters. The study was conducted for 4 monthes. The samples collected in experimental period were divided into three parts, obtaining thus a tri-replicate. Test diets consisted of 70% reference diets, 30% test ingredient and utilied 0.5% Cr2O3 as the non-digestible marker. Experiment І: Evaluation of the effect of digestibility by faeces collection (stripping and settling-every hour). The apparent digestibility coefficient for nutrient was 0.36%~3.07% being lower for stripping than for settling. According to the settlement period (1、2、3、6 hours) the nutrients in the faeces became lower. The effect of digestibility by the two collection methods especially appears on protein and nitrogen free extract. The result is suggested that the stripped faeces contains residues of not yet digested nutrients, and collected faeces with settling methods result leaching of nutrients into water. Considering the low effect (< 4%) and the less working and handling time, netting shows to be a better method for collecting faeces. Experiment П: Determination of digestibility coefficients of α-starch, wheat flour, wheat gluten, corn gluten, brown fish meal, white fish meal, squid viscera meal, defatted soybean meal, full fat toasted soybean meal by collecting faeces with settling in net method every hour. The result shows that protein digestibility for all of the ingredients is between 87.96%~101.87%, and lipid digestibility is between 85.00%~96.71%. Grouper was capable of digesting protein and lipid very effectively in almost all of the ingredients tested no matter either the ingredients is from a plant-source or animal-source. The digestibility of nitrogen free extract (NFE) in all ingredients was lower, except for α-starch, meaning the gelatinisation of starch is effectively advantageous for grouper. Digestible energy will become lower when the NFE content of the ingredients added is high. Finally, according to the digestibility coefficients, plant protein sources can be used instead of animal protein source in grouper artificial diets, provided the starch gelatinizes to make sure the high digestibility.