水产动物营养与饲料学－双语教学课件chapter 4-Digestibility and Absorption.ppt

Chapter 4 Digestibility and Absorption General 1. Methods of digestibility determination* 2. Factors affecting digestibility 3. Nutrient digestibility General The nutritional value of a feedstuff （营养价值）? Definition of the bioavailability (1) in term of digestibility（消化率） (2) in the case of energy, metabolizability（可代谢性） 1. Methods of digestibility determination（消化率的测定方法） 1.1 Indirect Method（间接法） 1.2 Direct method（直接法） 1.3 Assay diets (测定饲料) 1.1 Indirect Method Determination principle nondigestible marker （不可消化的标记物） chromic oxide (Cr2O3)（三氧化二铬） 0.5 to 1.0 percent in the diet Y2O3 （钇） 100ppm * Digestibility coefficient of nutrient =100－100×percent marker in feed×percent nutrient in feces percent marker in feces×percent nutrient in feed 营养素的消化率＝100－100×（饲料中指标物的含量/ 粪便中指标物的含量 ×粪便中营养素的含量 / 饲料中营养素的含量） Digestion coefficients for energy, crude protein, carbohydrates, lipids, and dry matter. The advantages of indirect method（间接法的优点） (1) It eliminates the need to quantitatively collect all of the excreta（不需要收集全部的粪样） , (2) and the test fish can eat voluntarily（而且试验鱼还能够自由采食） . Feces collection（收粪） Proper fecal collection to prevent loss of soluble nutrients into the water is critical in digestion trials. （正确的收粪方法可以防止可溶性养分在水中的损失，这在消化试验中十分关键） The calculation of digestibility when a significant amount of soluble nutrients have leached from the feces gives digestion coefficients that are erroneously high.（如果有显著量的可溶性氮已从粪中渗出，就会使消化率错误地偏高） Some investigations to collect the feces (1) Directly from the rectum using anal aspiration（肛门吸出法直接从直肠收集） ， (2) Surgical excision（外科切除法） ， (3) Stripping to minimize the problem of nutrient leaching（或剥离法直接从直肠收集粪样，降低养分渗出）， (4) Siphoned out of tank. 1.2 Direct Method（直接法） ? Determination principle all the feed consumed by the fish,（需要测定鱼摄食的全部饲料量） and all of the resulting excreta.（和全部的排粪量） The disadvantages of direct method（直接法的缺点） fish are immobilized（鱼的活动受限）， force-fed（