1、Protein and Energy Metabolism in Rumen and Their Applications in Diary Nutrition 瘤胃中蛋白、能量代谢机制及其在日粮营养中的应用Qingping Liu Ph.D.,Kevin Halpin Ph.D.International Ingredient CorporationSt.Louis,MO 63026USAOutline提纲Ruminant Protein NutritionRuminant Energy NutritionInteraction of Protein and Energy in Rumina
2、nt NutritionMicrobial Protein and its Importance in ruminant NutritionIntake and Milk ProductionRumenBitoticTM and its applications 反刍动物蛋白营养研究反刍动物能量营养研究反刍动物蛋白及能量间的互作效应菌体蛋白及其在反刍动物营养中的重要性采食量及产奶量百泰-R及其应用Anaerobic Fermentation in Rumen瘤胃中的厌氧发酵It is all about the bugs in rumen Rumen volume of lactating c
3、ow=120,000 ml Rumen bacteria:10,000,000,000/ml Rumen protozoa:1,000,000/ml Ruemn fungi:1,000/mlFeed rumen bugs=feed the cows我们来看看这些瘤胃中的我们来看看这些瘤胃中的“小东西小东西”泌乳牛的瘤胃体积=120,000/ml 瘤胃细菌：10,000,000,000/ml 瘤胃原虫：1,000,000/ml 瘤胃真菌:1,000/ml饲喂微生物=饲喂奶牛Ruminant Protein Nutrition反刍动物蛋白质营养More appropriate:Rumen Nitr
4、ogen Metabolism或者称为瘤胃中氮的代谢更为恰当General Information一些常识 No proteases in saliva 唾液中不含蛋白酶 No rumen secretions 瘤胃不分泌体液 Microorganisms responsible for protein digestion in rumen(and reticulum)在瘤胃（网胃）中微生物负责蛋白的消化 Bacteria 细菌 Protozoa 原虫 Sources of Rumen Nitrogen瘤胃的氮来源Feed 饲粮中饲粮中 Protein nitrogen 蛋白氮 Protein
5、 supplements(SBM,CSM,grains,forages,silages.蛋白补充（豆粕,棉籽饼粕,谷物，粗饲料，青贮饲料）Non protein nitrogen(NPN)非蛋白氮 Usually means urea 常规方法 尿素 However,from 5%of N in grains to 50%of N in silage and immature forages can be NPN 然而，非蛋白氮在谷物中的含量约5%、青贮牧草以及未成熟牧草中约50%Endogenous(recycled)N 内源（循环）氮来源 Saliva 唾液 Rumen wall 瘤胃壁R
6、uminal Protein Degradation瘤胃降解蛋白的降解Fermentative digestion（利用发酵消化）enzymes of microbial origin 微生物分泌的酶 MO proteases&peptidases cleave peptide bonds and release AA 微生物蛋白酶及肽酶分裂肽键释放出氨基酸 AA deaminated by microbes,releasing NH3 and C-skeleton 然后微生物将氨基酸脱氨基，分解为NH3 及碳架 MOs use NH3,C-skeleton and energy to syn
7、thesize their own AA 微生物利用NH3，碳架及能量用来合成其所能利用的氨基酸 Energy primarily from CHOs(starch,cellulose)能量主要来源于碳水化合物（淀粉，纤维素）Formation of NH3 rapid.very few free AA in rumen 瘤胃中NH3快速形成，游离氨基酸数量很少NPN Utilization非蛋白氮的利用 Urea(and most sources of NPN)rapidly degraded to NH3 尿素（非蛋白氮的主要来源）迅速降解为氨 MOs dont care where NH
8、3 comes from 微生物只单纯利用NH3，而不介意其来源Limitations of Microbial Protein Synthesis微生物蛋白合成的局限性 Two most likely limitations 两个最有可能的局限性 Energy available 可利用能量 NH3 available 可利用的NH3 These need to be synchronized 两者供应必须同步 For diets containing urea,may also need 含有尿素的日粮还需要一些营养物质 Sulfur(for S-containing AA)硫（合成含硫氨
9、基酸）Branched-chain C-skeletons 含有支链的碳链 MO cannot make branched-chain C-chains 微生物不能制造支链碳链 These normally not a problem 通常这些不构成问题Overflow Ammonia氨浓度过高时 Shortage of energy relative to available NH3 相对于可利用NH3，能量呈现缺乏 Liver:NH3 Urea 肝脏：NH3 尿素 Urea recycled or excreted,depending on animal needs 尿素参与循环还是排出，
10、取决于动物的需要 Saliva 唾液 Rumen wall 瘤胃壁Protein Leaving Rumen蛋白离开瘤胃途径 Microbial protein 微生物蛋白 Escape protein(also called“bypass”protein)瘤胃非降解蛋白（也称为过瘤胃蛋白）Enter abomasum&small intestine 进入皱胃及小肠 Digested by proteolytic enzymes similar to nonruminants、与单胃相同，通过蛋白酶进行分解 Escape vs Bypass protein 过瘤胃蛋白的命名问题 Technic
11、ally not“bypass”从技术角度不适合称为过瘤胃 Reticular groove 食管沟Protein UtilizationRuminant vs Nonruminant反刍动物与单胃动物对于蛋白的利用Similarities and Dissimilarities相同点及不同点Ruminant vs Nonruminant Similarities相同点1.At tissue level Metabolic pathways similar2.Ruminant tissues can synthesize dispensable AA3.Cannot synthesize in
12、dispensable AAEssential AA must be provided from digestive tract4.Tissue proteins constantly undergoing turnover5.AA not stored6.Constant supply of AA required1.组织水平上-代谢路径相同2.反刍动物自身也可合成非必需氨基酸3.不能合成必需氨基酸 -必需氨基酸必须从消化道提供4.组织蛋白不断经历分解再合成的循环5.氨基酸在体内不储备6.为满足氨基酸需要，保证持续的供应Carbohydrate Nutrition In Ruminant反刍
13、动物碳水化合物营养Nutrient Fractions 营养组分营养组分Amino Acids ProteinNon-Protein Nitrogen FatFeedstuff饲料原料Sugars&Starches-NFC Carbohydrate ADFCrude Fiber NDF Ash-Mineral蛋白脂肪碳水化合物矿物质氨基酸非蛋白氮糖、淀粉-非结构性碳水化合物酸性洗涤纤维酸性洗涤纤维中性洗涤纤维中性洗涤纤维Carbohydrate Digestion in Ruminants反刍动物碳水化合物消化生理 Ingested feed is exposed to extensive 摄
14、取的饲料被分解，内部营养物质广泛暴露 pregastric fermentation 前胃发酵 Most ingesta fermented by microbes before it is exposed to typical gastric and small intestinal enzymes 许多营养物质在接触胃及小肠的酶前，已经被微生物发酵 Rumen fermentation is highly efficient 瘤胃发酵效率很高Reticulorumen瘤网胃 Favorable environment for survival and activity of anaerob
15、ic microbes 瘤胃内环境有益于厌氧微生物的生存及活动 1 billion bacteria/ml 1000,000,000 个细菌/ml Warm,moist environment 温暖湿润的内环境 Ferment cellulose,starch,and soluble carbohydrate 发酵纤维素、淀粉、可溶性碳水化合物 Almost all carbohydrate is fermented in the rumen 几乎所有的碳水化合物都在瘤胃中发酵 Some bypass starch may escape to the small intestine一些过瘤胃淀
16、粉可能会到达小肠 Do not have salivary amylase,but have plenty of pancreatic amylase to digest starch 不分泌唾液淀粉酶，但分泌大量胰腺淀粉酶来消化淀粉Microbial Populations微生物 Celluloytic bacteria(fiber digesters)纤维分解菌 produce cellulase-cleaves 14 linkages 产生纤维素分解酶分解14 糖苷键 prefer pH 6-7 适宜pH 6-7 utilize N in form of NH3 以氨源的形式利用氮 re
17、quire S for synthesis of sulfur-containing amino acids(cysteine and methionine)需要硫元素用于合成含硫氨基酸（met和cys）produce acetate,propionate,little butyrate,CO2产生乙酸、丙酸、丁酸及CO2 predominate in animals fed roughage diets在以粗饲料为主的日粮中占主导地位Microbial Populations 微生物 Amylolytic bacteria(starch,sugar digesters)淀粉分解菌（消化淀粉和
18、糖）digest starch 消化分解淀粉 prefer pH 5-6 适宜pH 5-6 utilize N as NH3 or peptides 以NH3源及肽的形式利用氮 produce propionate,butyrate and lactate 产生丙酸、丁酸及乳酸 predominate in animals fed grain diets 在以谷物为主的日粮中占主导地位 rapid change to grain diet causes lactic acidosis 日粮快速改变为谷物饲料容易导致酸中毒(pH快速降低)(rapidly decreases pH)Strepto
19、coccus bovis 牛链球菌 ADP ATPNADP+NADPHSugars糖CatabolismBiosynthesisGrowth Maintenance ReplicationMicrobial Metabolism 微生物代谢VFACO2CH4Heatin rumen:烟酰胺腺嘌呤二核苷酸磷酸（还原态）烟酰胺腺嘌呤二核苷酸磷酸（还原态）NADPH+三磷酸腺苷三磷酸腺苷 ATP;VFA 挥发性脂肪酸挥发性脂肪酸分解代谢分解代谢生物合成代谢生物合成代谢在瘤胃中在瘤胃中生长维持生长维持Bacterial Digestion of Carbohydrates微生物对碳水化合物的消化Mic
20、robes attach to(colonize)fiber components and secrete enzymes 微生物附着于纤维素上，并分泌酶微生物附着于纤维素上，并分泌酶 Cellulose,hemicellulose digested by cellulases and hemicellulases 分泌纤维素酶及半纤维素酶用于分解纤维素及半纤维素 Complex polysaccharides are digested to yield sugars that are fermented to produce VFA 多糖类被消化用于产生糖类，后者发酵生成挥发性脂肪酸 Sta
21、rches and simple sugars are more rapidly fermented to VFA 淀粉及单糖类被迅速发酵生成挥发性脂肪酸Protozoa engulf starch particles prior to digesting them 原虫在消化淀粉前先吞噬淀粉颗粒Rumen:瘤胃：Ruminant Carbohydrate Digestion反刍动物对碳水化合物的消化Small Intestine 小肠 Secretion of digestive enzymes 分泌消化酶 Digestive secretions from pancreas and liv
22、er主要由胰腺及肝脏分泌消化液 Further digestion of carbohydrates进一步消化碳水化合物 Absorption of H2O,minerals,amino acids,glucose,fatty acids吸收水、矿物质、氨基酸、葡萄糖、脂肪酸Bacterial population ferments the unabsorbed products of digestion微生物发酵那些无法消化的组分 Absorption of H2O,VFA and formation of feces吸收水、挥发性脂肪酸，合成排泄物Cecum and Large Intes
23、tine 盲肠及大肠Carbohydrate Digestion Rate碳水化合物的消化率Composition and Digestion of Carbohydrate Fractions碳水化合物的组成及消化_Composition 组成 Rumen Digestion(%/h)瘤胃消化率%/h_Sugars 糖类 200-350Organic Acids 有机酸 1-2Starch 淀粉 10-40Soluble Available Fiber 可溶性可利用纤维 40-60 Pectins 果胶 B glucans 葡聚糖 Insoluble Available Fiber 非可溶性
24、可利用纤维 2-10 Cellulose 纤维素 Hemicellulose 半纤维素Unavailable Fiber(lignin)非可利用纤维素（木质素）0_糖类糖类淀粉淀粉纤维素纤维素发酵发酵时间时间Volatile Fatty Acids挥发性脂肪酸CarbohydratesVFAsGlucoseMicrobial Fermentation Short-chain fatty acids produced by microbes 3 basic types:3 种基本形态-Rumen,cecum,colonAcetic acid(2c)乙酸CH3COOCH2COOCH3CH2COOC
25、H2CH3Propionic acid(3c)丙酸Butyric acid(4c)丁酸碳水化合物碳水化合物微生物发酵微生物发酵挥发性脂肪酸挥发性脂肪酸葡萄糖葡萄糖瘤胃、盲肠、结肠中短链脂肪酸由微生物合成VFA Formation挥发性脂肪酸构成+CH4+heat+CH41 GlucoseVFAs absorbed passively from rumen to portal bloodProvide 70-80%of ruminants energy needs 1分子葡萄糖分子葡萄糖 2 醋酸盐醋酸盐热量热量2 丙酸盐丙酸盐水水1 丁酸盐丁酸盐挥发性脂肪酸由瘤胃被动吸收入血，提供反刍动物能量
26、需要的挥发性脂肪酸由瘤胃被动吸收入血，提供反刍动物能量需要的70-80%Rumen Fermentation瘤胃发酵 Gases(carbon dioxide and methane)are primary byproducts of rumen fermentation 二氧化碳及甲烷是瘤胃发酵主要副产物 Usually these gases are eructated or belched out-if not,bloat occurs 通常这些气体都通过打嗝的形式排出，如果不能顺利排出会造成瘤胃胀气 Bloat results in a severe distension of the
27、 rumen on the left side of the ruminant and can result in death 瘤胃胀气会导致反刍动物左侧瘤胃剧烈膨胀，严重时会死亡Uses of VFA挥发性脂肪酸的利用 Acetate 乙酸 Energy 能量 Fatty acid synthesis 脂肪酸合成 Propionate 丙酸 Energy 能量 Gluconeogenic糖异生 glucose synthesis 葡萄糖合成 Butyrate 丁酸 Energy 能量 Rumen epithelial cells convert to ketone 瘤胃上皮细胞转化成酮体 P
28、roportions produced depends on diet 根据日粮组成不同，比例不同 Absorption of VFAs挥发性脂肪酸的吸收No evidence for active transport 没有证据证明是主动运输吸收VFA metabolism in the rumen wall挥发性脂肪酸在瘤胃壁的代谢Cells use most of the butyrate for their own energy needs细胞利用了大部分丁酸用于自身的能量需要Acetate and propionate are exported to blood乙酸盐与丙酸盐被吸收入血
29、VFA Production Molar Ratios挥发性脂肪酸的产生Forage:Grain粗精比Acetate乙酸Propionate丙酸Butyrate丁酸100:071.416.07.975:2568.218.18.050:5065.318.410.440:6059.825.910.220:8053.630.610.7Rumen VFA Profiles瘤胃挥发性脂肪酸概况乙酸丙酸乳酸纤维分解菌活性强 淀粉分解菌活性强瘤胃pHMetabolism of VFA挥发性脂肪酸的代谢Overview 综述Acetate and butyrate are the major energy s
30、ources(through oxidation)乙酸及丁酸是主要的能量来源（通过氧化途径）Propionate is reserved for for gluconeogenesis丙酸主要储备用于糖异生Acetate is the major substrate for lipogenesis乙酸是脂肪生成过程中最重要的底物Hence the importance of fiber in dairy diets to maintain milkfat levels因此 粗纤维在日粮中的重要性主要是用来维持乳脂水平Propionate is also lipogenic(though glu
31、cose)丙酸也可用于生成脂肪（通过生成葡萄糖）Metabolism of VFAs 挥发性脂肪酸代谢Van Soest,1994AcetateButyratePropionate琥珀酰辅酶琥珀酰辅酶A脂肪脂肪乙酰乙酸乙酰乙酸-羟基丁酸羟基丁酸 乙酰辅酶乙酰辅酶A柠檬酸柠檬酸甘油甘油丙酮丙酮苹果酸苹果酸乙酰辅酶乙酰辅酶A草酰乙酸草酰乙酸磷酸烯醇式丙酮酸磷酸烯醇式丙酮酸 乙酸乙酸丁酸丁酸丙酸丙酸Glucose Requirements葡萄糖需要There is less fluctuation in blood glucose in ruminants and blood glucose is
32、lower at 40-60 mg/dl反刍动物血糖浓度波动很小，而且血糖一般低于 40-60 mg/dlReduced fluctuation due to:血糖浓度稳定的原因 Eat more constantly than monogastrics 与单胃动物相比，采食过程更稳定，持续时间长 Continuous VFA production 挥发性脂肪酸不断产生 Continuous digesta flow 持续不断的食物流 Continuous gluconeogenesis 持续的糖异生作用Digestive Feature消化功能消化功能Ruminant反刍动物反刍动物Nonr
33、uminant非反刍动物非反刍动物Salivary amylase唾液淀粉酶唾液淀粉酶Zero 无High primates 高-灵长类Moderate-pig中-猪Low-carnivores低-肉食动物Pregastric fermentation前胃发酵前胃发酵High+很高很高Zero无Gastric胃胃Very low 很低Very low很低Pancreatic amylase in SI小肠胰腺淀粉酶小肠胰腺淀粉酶Low to moderate低-中等程度High高Glucose absorption from SI小肠葡萄糖吸收小肠葡萄糖吸收Zero to low很低几乎无Hi
34、gh高Post SI小肠后段小肠后段Low低Low to High低-高Carbohydrate Digestion and Absorption碳水化合物的消化及吸收Fats 脂肪脂肪Increase energy density in ration 增加日粮能量浓度 Do not supply energy to microbes!并不为微生物提供能量！并不为微生物提供能量！Unpalatable,tend to decrease feed intake适口性差，容易降低采食量 Over 3%in ration will suppress feed intake 超过3%会降低采食量 Ca
35、n supplement with“rumen protected”fats 可以以过瘤胃脂肪形式补充Suppress microbial function 抑制微生物生长及生理功能抑制微生物生长及生理功能 Form“soaps”in rumen 瘤胃中以皂化脂肪形式存在 PUFAs greater negative effect than SFAs 多不饱和脂肪酸的抑制效应要高于饱和脂肪酸 Decrease fiber digestibility,slow rate of passage 降低纤维素的消化率，减缓瘤胃流通速率Oilseeds are“slow-release”form of
36、fat,less negative effects in rumen籽实类油属于缓慢释放性油脂，对瘤胃微生物的影响较小Overview of Carbohydrates and Ruminants反刍动物碳水化合物代谢综述Diet Protein Carbohydrate Fat _Rumen_Blood_TissueBacterial ProteinAmino AcidsProteinStarch VFAPropionate Acetate ButyrateGlucoseLactoseFatty AcidsFatty AcidsFat日粮日粮蛋白蛋白碳水化合物碳水化合物脂肪脂肪瘤胃瘤胃微生物
37、蛋白微生物蛋白淀粉淀粉挥发性脂肪酸挥发性脂肪酸脂肪酸脂肪酸乙酸乙酸丁酸丁酸丙酸丙酸血液血液氨基酸氨基酸葡萄糖葡萄糖乳糖乳糖脂肪酸脂肪酸脂肪脂肪组织组织蛋白蛋白Feeding Order饲喂程序饲喂程序 Feeding forage before feeding concentrates(in component-fed herds where forages and concentrates are fed separately)will buffer rumen before large amounts of acids are produced 在饲喂精料前饲喂粗饲料（当粗饲料与精饲料分开
38、饲喂时）能够保证瘤胃在大量酸产生前起到缓冲效果。More stable rumen environment 更加稳定的瘤胃内环境 Better forage digestibility,faster rate of passage,and increased cow performance compared to feeding forages after concentrates 与先饲喂精料再饲喂粗饲料相比，能够提高粗饲料消化率，提高瘤胃排空速度，提高奶牛的生产性能Interaction of Protein and Energy in Ruminant Nutrition反刍动物营养中的
39、能量与蛋白的互作发酵发酵糖类糖类淀粉淀粉纤维素纤维素时间时间Rumen NH3 Following Protein Ingestion采食蛋白后瘤胃氨浓度变化亚麻籽粕亚麻籽粕尿素尿素豆粕豆粕鱼粉鱼粉采食后经过时间采食后经过时间Rumen VFA from Carbohydrate Sources瘤胃不同碳水化合物来源的挥发性脂肪酸浓度淀粉淀粉玉米玉米破碎玉米破碎玉米纤维素纤维素时间时间挥发性脂肪酸挥发性脂肪酸Matching Available Energy with Rates of Protein Degradation蛋白降解与可利用能量的同步To maximize efficiency
40、 of microbial protein synthesis from ammonia,available energy must be present.为使微生物利用氨合成蛋白的效率最大化必须同时提供足够的有效能Matching Protein and Energy Sources同步蛋白与能量来源Rumen Degradable Protein瘤胃降解蛋白瘤胃降解蛋白(RDP)About 60%of protein in the ration should be rumen degradable(RDP)to meet needs of microbes 日粮中必须保证60%的蛋白为RD
41、P以满足微生物需要 30%of the protein should be rumen soluble for component-fed herds 日粮中蛋白的30%必须在瘤胃中可溶 45%should be rumen soluble in TMR-fed herds 在全混合日粮中粗蛋白的45%必须是瘤胃可溶性蛋白 Soybean meal is rumen soluble 豆粕属于瘤胃可溶性蛋白源 Corn gluten is an insoluble protein source 玉米蛋白粉属于瘤胃不可溶性蛋白源Rumen Undegradable Protein(RUP)瘤胃非降
42、解蛋白瘤胃非降解蛋白Protein that“by-passes”rumen degradation to meet the needs of the cow that are not met by microbial protein production过瘤胃降解蛋白也许适合反刍动物自身需要，但并不适于微生物产生菌体蛋白Should be about 40%of total nitrogen fed瘤胃非降解蛋白应该在总日粮氮中占到40%Sources include heat-treated soybeans,fish or meat meal,distillers grains来源应该包
43、括热处理豆粕，鱼粉及肉粉以及酒糟Optimal LYS:MET ratio is 3:1 适宜的赖氨酸蛋氨酸比为3：1 Typically requires overfeeding protein to meet methionine needs of cow 通常需要过量的蛋白质，以满足奶牛蛋氨酸的需要 Can meet needs with lower RUP and supplemental rumen-stable methionine supplements($)可以提供更低含量的RUP，同时提供过瘤胃保护性蛋氨酸Non-Fiber Carbohydrates(NFC)非结构性碳水化
44、合物非结构性碳水化合物 Sugars and starches 糖及淀粉 Produce VFAs 产生挥发性脂肪酸 Rapidly digested 快速被消化 Can change rumen pH quickly!快速改变瘤胃pH！Meet energy needs of microbes 适宜的微生物的能量需要 Require about 38-40%in ration for this need 需要从日粮来源提供38-40%Can be a challenge in high-fat diets 可能被高脂肪日粮改变 On paper,energy needs of cow are
45、 met,but ration is actually energy deficient for optimal rumen microbial synthesis 传统研究认为，奶牛日粮中的能量是适合的，但实际上为满足最佳的瘤胃微生物合成，日粮中的能量是缺乏的What Are NFCs?什么是非结构性碳水化合物什么是非结构性碳水化合物 Non-Fiber Carbohydrates(NFCs)are extremely important sugar and starch components of a dairy ration.非结构性碳水化合物是奶牛日粮中极其重要的组分非结构性碳水化合物
46、是奶牛日粮中极其重要的组分 NFCs are more rapidly degraded in the rumen than fibrous carbohydrates.They provide immediate necessary energy for rumen microorganisms to synthesize protein for cell growth.非结构性碳水化合物与结构性碳水化合物相比降解更加快。它们为瘤胃微生物合成蛋白及细胞生长提供必须的能量 NFC=100-(NDF+CP+Fat+Ash+Moisture)NFC=100-(中性洗涤纤维中性洗涤纤维+粗蛋白粗蛋白
47、+脂肪脂肪+灰分灰分+水水)Optimum NFC and Sugar Levels适宜的适宜的NFC及糖水平及糖水平 The optimum NFC is generally set at a 40%of the ration dry matter.日粮中适宜的NFC水平一般为40%，以绝干物质计 A minimum level of 35%NFC is generally recommended to assure maximum efficiency of microbial growth.一般建议采用最少35%的NFC水平，用以保证微生物合成的最大效率 A maximum level
48、of 45%is often set to prevent disruption of fiber digestion due to low rumen pH.最高推荐量是45%，防止瘤胃pH过低破坏粗纤维的消化 Optimum Sugar levels in the ration are typically recommended to be between 4 to 6%.建议适宜的糖类水平为4-6%Why Differentiate Between Starch and Sugar in NFC Fraction?为什么淀粉及糖类在为什么淀粉及糖类在NFC中不同中不同Because.因为
49、因为 Sugars ferment much faster in the rumen than starches.糖类在瘤胃中的发酵速度要远远快于淀粉Sugars Digested within 30-60 minutesStarches Digested within 2-6 hours 糖类-在30-60分钟内消化 淀粉-在2-6个小时内消化Recent research indicates that a cocktail of different sugars may provide some benefits in rumen digestion,as compared to a si
50、ngle sugar source.近些年来的研究表明，使用不同类型的糖类复合使用，效果要好于单一的糖类Feeding a variety of sugars feeds all of the rumen microbes which improves forage digestion and utilization饲喂不同种类糖能够改善瘤胃微生物粗饲料的消化及利用率This result is greater energy intakeThis helps improve forge intake since forge digestion can take place at increas
