1、Chapter 1-3Carbohydrates1. General2. Utilization of carbohydrate (CHO)3. Digestibility and importance of crude fibre 1. General1.1 Function of CHO(1) energy source(2) to assist the formation of the carbon skeleton for non-essential fatty acid （非必需脂肪酸的碳骨架）(3) for the synthesis of fats（合成脂肪）1.2 The cl
2、asses of carbohydrates（糖的分类）（糖的分类） Monosaccharides（单糖） Di- and oligosaccharides（二糖和寡糖） Polysaccharides（多糖） Monosaccharides（单糖） hexoses (glucose, galactose, fructose) pentoses they are the building blocks for formation of di-, oligo- and polysaccharides Di- and oligosaccharides（二糖和寡糖） monosaccharide
3、molecules are joined together by means of ether linkages （醚键） lactose, consist of -glucose and -glucose and is the sole disaccharide of animal origin sucrose, -glucose and -fructose maltose （麦芽糖）, two -glucose cellobiose (纤维二糖), two -glucose moleculesPolysaccharides（多糖） macromolecules composed of la
4、rge numbers of monosaccharidesStarchin the cells of plants in the form of granules（颗粒） of various sizes (1-150 m)each starch granule is composed of amylose (直链淀粉) (25%) ， 100-200 glucose molecules amylopectin (支链淀粉) (75%)，250-5000 glucose units Polysaccharides（多糖） Dextrin (糊精糊精) a water soluble brea
5、kdown product of starchGlycogen (糖原糖原) the animal starch, 5000-25000 glucose units, chiefly in the liver，some in the muscle. Polysaccharides（多糖）Cellulose （纤维素）（纤维素） the building material for plant cell walls, 2000-8000 -glucose units. Cellulases（纤维素酶）, the enzymes for cellulose cleavage（分解）, only pr
6、oduced by micro-organismsChitin （几丁质）（几丁质） forms the skeletal portions of crustaceans （甲壳类） insects， in the cell walls of yeasts（酵母）, Polysaccharides（多糖）Lignin（木质素）（木质素） in the cell walls of woody plants together with cellulose, not a carbohydrate, but a derivative of benzene(苯衍生物) indigestible，The
7、most important carbohydrates in fish glycogen, glucose, lactate (乳酸盐) pyruvate（丙酮酸盐）Glycogen（糖原）（糖原）muscle glycogen: 0.15%, about 6% of that in the liver liver glycogen: 2.5% of fresh weightGlycogen（糖原）（糖原） intense physical activity, （剧烈运动时）muscle glycogen broken down in a few minutes, recovery phas
8、ethe original level is not reattained even 24 hours later,liver glycogen content diminishes markedly.（肝糖原含量显著减少）1.3 Determination of carbohydrateNot by direct analysis, but by difference（差额） after the contents of moisture, crude protein(CP), fat(EE), ash, and crude fibre (CF). includes the water-sol
9、uble carbohydrate and certain other materials, but not the crude fibre（粗纤维） * N-free extract, NFE(无氮浸出物) =100% - moisture% - CP% - EE% - ash% - CF%Crude fibre include: cellulose, lignin, pentosans（戊聚糖）1.4 Factors affecting the blood-glucose content of the fish(1) the time of feeding (2) the quality
10、of diet(3) intense activity(1) the time of feeding (2) the quality of dietthe concentration of glucose in the blood rainbow trout, 35 - 50mg/100 ml carp, 30 - 47 mg/100 mlmaximum blood-glucose level occurred(1) the time of feeding (2) the quality of dietrainbow trout6 hours after high starch intake,
11、（摄入高淀粉饲料后）9 hours after high glucose intake,18 hours after high protein intake.carp2 hours after oral administration of glucose(3) intense activityincrease many times in the course of a few minutes dramatically the muscle lactate (乳酸盐)the blood lactate pyruvate (丙酮酸盐)at a slower rate2. Utilization o
12、f carbohydrate Warm-water fish can use much greater amounts of CHO than cold-water and marine fish.channel catfish the growth rate of fingerlings was greater when their diets contained some carbohydrates rather than only lipids for all the non-protein energy.the maximum tolerable concentration shoul
13、d be used with regard to the fish species.（饲料中应该最大限量地用糖类）* 2.1 The nutritional values of carbohydrate among fish(1) carbohydrate may serve as precursors for the dispensable amino acids and nucleic acids, （作为非必需氨基酸和核酸的前体）, which are metabolic intermediates necessary for growth.(2) the least expensive
14、 source of dietary energy, catabolized（分解）for energy(3) protein sparing effect of CHO(4) starch is also important for the binding properties of extruded and pelleted feeds.（淀粉对于膨化饲料和颗粒饲料的粘结性很重要）in natural diet in the wild ingest very little CHO, meet their energy requirements chiefly by breakdown of
15、 protein, makes use of amino acids for gluconeogenesis (葡糖异生), especially alanine serine, phenylalanine tyrosineDietary CHODigestive tract*-amylase, glucosidase (maltase, cellobiase, saccharase, lactase), galactosidase (lactase), fructosidase (saccharase), chitinase, chitobiase, * glycolysis, tricar
16、boxylic acid cycle (TAC), pentose phosphate shunt, gluconeogenesis, glycogen synthesisliver or kidney* 2.2 Utilization of carbohydrate in fish associated with Complexity of the carbohydrate （糖的复杂性） The ability of fish to use various sources of carbohydrateRed sea breamNo significant difference in gr
17、owth rate for the various carbohydrate sources.Channel catfishdextrin and starch were used for growthbut not mono- and disaccharides.Salmonidshigh concentration of digestible carbohydrates,results in an increase in liver size and glycogen contentSimilar effects in red sea bream, plaice, yellowtail.C
18、hum salmon fry (大麻哈鱼鱼苗)glucose, maltose, sucrose, dextrin, and gelatinized starch were used for growth,but not fructose, galactose or lactoseWhite sturgeon（美洲鲟）Glucose and maltose dextrin or starch.Chinook salmon （大鳞大麻哈鱼）20% of dietary CHO, growth rates in descending order:glucose, maltose and sucro
19、se,dextrin and fructose, galactose，potato starch, and glucosamineCarp (growth rate and FE)30% of dietary CHO, in descending order: maltosedextrinGlucose-starch The ability to use dietary carbohydrate among speciesCommon carpChannel catfishTilapia could use higher level of carbohydrates, 30%See P33,
20、Tab1-13 The ability to use dietary carbohydrate among speciesRainbow trout YellowtailSalmonids PlacieYellowtailRed sea bream 25% dextrin or gelatinized starch Oral glucose tolerance test （口服葡萄糖耐量实验）Phenomena : a persistent hyperglycemia (持续的高血糖) Reason: Relative inability to utilize high concentrati
21、ons of carbohydrates Low levels of endogenous insulin Non-insulin-dependent diabetes rather than insulin-dependent diabetes（更可能是非胰岛素依赖性糖尿病）have been conducted withBrook trout （溪红点鲑）Rainbow troutCommon carpGrass carpChannel catfishRed sea breamYellowtailSimilar with rainbow trout fed diets containing
22、 15% and 30% glucose Insulin levels in plasma during glucose tolerance tests （血浆胰岛素水平）Low in common carp red sea bream yellowtailInsulin was measured by a radioimmunoassay procedure (放射免疫测定法) using antiskipjack （抗鲣鱼）insulin serum. 3. Digestibility and importance of crude fibre Crude fibre （概念）A comp
23、lex of organic compounds which includesHigher proportions of vegetable matter in compound, higher level of crude fibre. cellulose lignin pentosansIn chinook salmon Small amount of -cellulose had a beneficial effect on growth and protein utilization.Large amounts had an adverse effect on growth.* The
24、 reasons for its benefits (1) More choice of feedstuff sources (拓宽原料来源)(2) Partial cellulose breakdown by micro-organisms in the intestine to give glucose(3) A slower rate of passage through the intestinal tract, consequently leading to a better utilization of the other dietary constituents.（通过肠道的速率
25、降低）With increasing CF uptake, the gastric evacuation rate （胃的排空率）also increased, while the digestibility of the dry matter decreased.Table 1 Effects of different CF contents on the apparent digestibility coefficiency (ADC) of dry matter, stomach evacuation time (minutes) and the ratio of stomach:bod
26、y weight （胃体比）in rainbow troutCF contents (%) 0 10 20 ADC of dry matter (%) 71 66 59 Stomach evacuation time (min) 782 379 412 stomach:body weight 1.4 1.8 1.9 See P35* Table 2 Optimum crude fibre content of diet in fish speciesFish species CF (%) Steelhead trout 10Black carp 8Leiocassis longirostris （长吻鮠） 48Grass carp 1015Wuchang fishBluntnose black bream （团头鲂） 1015Common carp 610Tilapia 310 Shrimp 5The end
