生长肥育猪的蛋白质与氨基酸营养课件

Protein and Amino Acid Nutrition of Growing and Finishing Pigs 生长肥育猪的蛋白质与氨基酸营养 Robert A. Easter, Ph.D. Professor of Swine Nutrition Dean, College of Agricultural, Consumer and Environmental Sciences University of Illinois Introductory Facts: Proteins are made up of amino acids 蛋白质由氨基酸组成 Amino acids are either essential (must be present in the diet) or nonessential (can be made by the animal). 氨基酸分为必需（日粮中必须有） 和非必需（动物可自体合成） The 10 essential amino acids are 十种必需氨基酸是: - Lysine 赖氨酸- Leucine 亮氨酸 - Tryptophan 色氨酸- Isoleucine 异亮氨酸 - Methionine蛋氨酸- Histidine 组氨酸 - Threonine苏氨酸- Phenylalanine 苯丙氨酸 - Valine 缬氨酸- Arginine 精氨酸 Introductory Facts: Pigs do not require protein per se but rather the amino acids that make up protein 猪本身不需要蛋白质，而是需要组成蛋白质的氨基酸 Amino acids in the diet are provided by protein-containing feeds (corn, soybean meal, sorghum, fish meal etc) 日粮中的氨基酸由含蛋白质的饲料组分(如玉米,豆粕,高粱,鱼粉等)提供 Amino acid progression: Dietary protein Free amino acids 游离氨基酸 Small intestine 小肠 Blood 血液 Protein synthesis Feces 粪 Urine 尿 日粮蛋白质 蛋白质合成 Typical Grower Diet 典型生长猪日粮 Ingredient 组分% Corn 玉米78.55 Soybean meal 豆粕19.05 Dicalcium phospate 磷酸氢钙 1.25 Limestone 石粉.74 Trace mineral salt 微量元素盐 .35 Vitamin premix 维生素.10 Total 总计100.00 The value of a protein source is dependent on its capacity to contribute digestible amino acids to the animal. The Chemical Score is a simple approach to assessing value 蛋白质来源的价值取决于为动物提供可消化氨基酸的能力，化学评分是 评定蛋白价值的简单方法 Amino acid Requirement, % Provided by diet, % Provided/ Requirement, % Lysine.75.5067.17 Threonine.48.4493.39 Tryptophan.12.12102.45 Isoleucine.46.47102.91 Met + CYs.41.45109.93 Histidine.22.34156.58 Leucine.601.29215.22 Valine.48.61127.97 Arginine.25.66264.38 The performance of an animal can be no greater than that made possible by the amino acid in least supply. This is commonly called the first limiting amino acid 最少量被提供的氨基酸制约了动物的生产性能，这种氨基酸通常称作第一限 制性氨基酸 Amino acid Requirement, % Provided by diet, % Provided/ Requirement, % Lysine.75.5067.17 Threonine.48.4493.39 Tryptophan.12.12102.45 Isoleucine.46.47102.91 Met + His.41.45109.93 Histidine.22.34156.58 Leucine.601.29215.22 Valine.48.61127.97 Arginine.25.66264.38 (First) (Second) Protein Synthesis Limiting Amino Acids in Some Common Feedstuffs 一些饲料原料中的限制性氨基酸 IngredientFirst Second Corn 玉米 Lysine 赖氨酸Tryptophan 色氨酸 Opaque-2 CornTryptophan 色氨酸Lysine 赖氨酸 Barley 大麦Lysine 赖氨酸Methionine 蛋氨酸 Wheat 小麦Lysine 赖氨酸Threonine 苏氨酸 Sorghum (milo)买罗高粱Lysine 赖氨酸Threonine 苏氨酸 Soybean meal 豆粕Met + Cys 蛋胱Threonine 苏氨酸 Cottonseed meal 棉籽粕Lysine 赖氨酸Threonine 苏氨酸 Peanut Meal 花生粕Lysine 赖氨酸? Fish meal 鱼粉Tryptophan 色氨酸? Comparison of Amino Acid Sources (Lysine as a percent of total protein) 氨基酸来源的比较（赖氨酸占总蛋白质的百分比） Item Crude protein, %Lysine, % Lysine as % of protein Pig 猪15.0.755.00 Corn 玉米8.5.252.94 Sorghum 高粱8.9.232.58 Wheat 小麦11.4.363.16 Rice bran 米糠14.0.614.35 Soybean meal 豆粕48.53.106.40 Cottonseed meal41.71.704.07 Peanut meal 花生粕49.01.452.96 Sesame meal45.01.262.80 Fishmeal 鱼粉61.24.745.62 棉籽粕 芝麻粕 Estimation of Limiting Amino Acids from Growth Data (A hypothetical example) 由生长性能数据估计限制性氨基酸 DietGain, kg/d 1. Corn-soybean meal, 12% CP.40 2. As 1 + Lysine.50 3. As 1 + Threonine.30 4. As 1 + Lysine + Threonine.60 Amino Acid Balance 氨基酸平衡 Amino acid balance refers to the proportional relationships among the amino acids 氨基酸平衡指氨基酸之间的比例关系 An amino acid imbalance reduces feed intake and growth rate. 氨基酸不平衡导致饲料采食量和生长速度下降 Performance of Chicks Fed Diets Formulated to a Lysine Requirement with Either an Imbalanced Protein or Crystalline Lysine 饲喂蛋白质不平衡或添加晶体赖氨酸日粮鸡的生长性能 Item Formulation Criteria Growth Performance DietLysine, % Protein % Gain, g Gain/ feed 1. Corn-soybean meal1.1020.3243.66 2. Corn-sesame meal.5620.368.34 3. As 2 + lysine1.1020.3222.61 4. Corn-sesame meal1.1038.0144.44 5. As 4 + lysine1.4638.0181.46 Baker and Easter (1976) Ideal Protein 理想蛋白质 The term, IDEAL PROTEIN, is used to describe the profile of dietary amino acids that would be perfectly in harmony with the pigs requirements That is a perfect balance. The concept of ideal protein originated in the 1930s in Dr. H. H. Mitchells laboratory at the University of Illinois. 所谓理想蛋白质，指日粮中的氨基酸组成完全符合猪的氨基酸需要，氨基酸之间完美 平衡。理想蛋白质的概念由伊力诺大学Mitchell博士的实验室于1930年提出。 - An optimum balance of amino acids 氨基酸之间的最佳平衡 - Exactly in the proportions in which the amino acids are required by the pig 氨基酸之间的比例关系与猪所需要的氨基酸比例完全一致 - Fully utilizable 可被完全利用 - A balance that cannot be improved by addition or substitution 这种平衡不能通过添加或替代而改善 From: M.F. Fuller, Rowett Res. Inst. Variations on Ideal Protein 各种理想蛋白质 Amino Acid Patterns, % of Diet Item Illinois Final Protein Illinois Ideal protein Wang & Fuller Protein NRC (1989) Protein Lysine.600.600.600.600 Arginine.290.250.250.250 Histidine.185.190.190.155 Tryptophan.095.110.110.110 Isoleucine.390.360.360.335 Leucine.600.600.660.445 Valine.415.410.450.355 Phe + Tyr.570.570.720.485 DL-Met + Cys.420.360.380.310 Threonine.390.390.430.355 Proline.200.200.200.200 Glycine.600.600.600.600 L-glutamate4.855.5.2704.9555.840 Chung and Baker, 1992 Growth Response to Different Amino Acid Patterns 不同氨基酸模型的生长反应 Item Amino Acid Pattern, % of Diet Illinois final protein Illinois ideal protein Wang & Fuller Ideal protein NRC (1988) Protein Gain, g/d219274235206 Feed, g/d553640570501 Gain/feed396428412411 Chung and Baker (1992) Digestible Ideal Amino Acid Patterns for Pigs 猪的可消化理想氨基酸模型 Amino acid Ideal AA Pattern, % of Lysine 10-20 kg20-50 kg50-110 kg Lysine100100100 Arginine423018 Histidine323232 Tryptophan171219 Isoleucine606060 Leucine100100100 Valine686868 Phe + Tyr959595 Met + Cys606264 Threonine656770 From Baker (1997) Utilization利 用 The pig cannot absorb intact proteins, except just after birth. Proteins are broken down by enzymes in the small intestine and individual amino acids are absorbed. 除非刚出生，否则猪不 能吸收完整蛋白质。蛋白质在小肠被酶降解，以个别氨基酸的形式被 吸收 AVAILABILITY- the portion of the chemically present amino acids that are used for growth 利用率用于生长的氨基酸占摄入氨基酸的百分比 DIGESTIBILITY - the portion of the chemically present amino acid that disappears in the small intestine. 消化率在小肠被吸收的氨基酸占摄入氨基酸的百分比 Not all amino acids in the diet are absorbed, not all amino acids that are absorbed are used for protein synthesis. 日粮中并非所有 氨基酸都能被吸收，并非所有被吸收的氨基酸都能用于蛋白质合成 Definitions 定 义 Apparent amino acid digestibility (Amino acid consumed / amino acid passed from ileum) x 100 氨基酸表观消化率，（采食的氨基酸 / 经过回肠的氨基酸 ） 100 True amino acid digestibility amino acid consumed / (amino acid passed from ileum endogenous secretions) x 100 氨基酸真实消化率， 采食的氨基酸 / （经过回肠的氨基酸体内 分泌的氨基酸） 100 From Kidder and Manners (1978) Some Apparent Ileal Digestibilities, % 某些回肠表观消化率 Feedstuff 原料LysineTryptophanThreonine Barley 大麦737370 Blood meal 血粉81-5 Canola meal 双低菜粕7567- Yellow corn 黄玉米807073 Fish meal 鱼粉80-76 Oats (grain) 燕麦585953 Peanut meal 花生粕79- Sorghum grain 高粱807573 Soybean meal -Hi-pro857874 Soybean meal 豆粕878177 Sunflower meal 葵花粕72-71 Wheat 小麦807874 NRC, 1998 高蛋白豆粕 True Ileal Amino Acid Digestibilities 回肠氨基酸真实消化率 (Bellaver, 1989) Amino acidCorn Wheat Mids Soybean meal Cotton seed meal Poultry by- product meal Meat and bone meal Arg94.394.996.592.889.888.2 His78.573.986.579.377.474.5 Ile78.972.587.473.680.674.6 Leu83.367.384.272.178.674.4 Lys59.960.086.159.778.175.9 SAA86.275.991.883.081.779.2 Phe84.578.187.984.180.178.3 Thr71.759.682.971.574.169.1 Trp68.473.382.873.961.560.8 Val79.372.786.076.978.976.4 Lab Tests for Digestibility 消化率的实验室测定 FDNB - 2,4 flurodinitrobenzene (Carpenter method) FDNB binds with the epsilon amino group of lysine, if it is not bound to some other moiety, to form a color. It is assumed that non-bound amino nitrogen is correlated with higher digestibility. 2,4 氟二氮苯（卡本特法），FDNB与赖氨酸分子中未与其它基团结合的 - 氨基结合 ，产生颜色反应。据认为未被结合的氨基氮与较高的消化率有关。 Pepsin digestibility - Incubate a sample of feed with pepsin and monitor nitrogen release. 胃蛋白酶消化率将饲料样品与胃蛋 白酶共同培养，检测氮的释放量。 Time, hours时间，小时 Nitrogen release, % 氮释放， Lab Tests for Digestibility 消化率的实验室测定 Multienzyme assay Incubate sample with a mixture of peptidase, trypsin and chymotrypsin and monitor pH change over time. Liberated carboxyl groups release hydrogen ions resulting in a pH drop 复合酶法将样品与肽酶，胰蛋白酶，胰凝乳蛋白酶共同培养 ，观察pH值 随时间的变化。游离的羧基基团释放氢离子，导致pH下降。 Multienzyme pH True lysine Feed Ingredientchange (units) digestibility Casein酪蛋白 2.36 99 Soybean meal豆粕 1.52 92 Poultry by-product禽副产品1.37 84 Meat meal 肉粉 1.37 85 Cottonseed meal 棉籽粕 1.23 72 Feather meal羽毛粉 0.90 68 Bellaver (1989) and Parsons (unpublished) 饲料组分 赖氨酸真 消化率 复合酶 pH 变化 Lab Tests for Digestibility 消化率的实验室测定 Protein Solubility Assay - 1.5 mg of protein placed in a 250 ml beaker with 75 ml of 0.2% KOH, stir for 20 minutes at 22o C, collect supernatant, centrifuge at 1250 x G for 10 minutes and analyze for protein. Express as percent of protein in original sample. 蛋白质溶解性法 Protein solubility, % Autoclaving time, minutes 自溶时间，分钟 Lab Tests for Digestibility 消化率的实验室测定 Prediction equations - based on correlations of physical and chemical measurements to digestiblity 预测方程 - 以对消化率的物理和化学检测之间的相关关系为基础 Near-infrared Reflectance Spectroscopy - based on comparison of the reflectance spectra of an unknown sample to a standard (calibration data set) 近红外反射光谱法 - 比较未知样品与标准品的反射光谱 Wavelength (nm) 波长，纳米 Reflectance - Log (1/R) Standard Unknown Formulation with True Digestible Amino Acids Item, %12345 Corn82.0780.3880.6579.9380.44 Soybean meal13.87- Poultry by-product meal-6.266.525.876.33 Cottonseed meal-5.005.005.005.00 Wheat bran5.005.005.005.00 Soybean oil-1.331.081.721.25 Wood cellulose1.28.03 Limestone.78.65.64.67.65 Dicalcium phosphate1.32.47.43.52.46 Mineral mixture.35.35.35.35.35 Vitamin mixture.10.10.10.10.10 L-Lysine HCl-.15-.33- DL-Methionine.02-.08- L-Threonine-.04-.12- L-Tryptophan-.02-.05.02 Bellaver (1989) Formulation with True Digestible Amino Acids 根据真可消化氨基酸配制的日粮Item 12345 Digestible 可消化氨基酸 Lysine.48.48.49.59.59 Methionine + Cystine .47.47.51.51.51 Threonine.37.36.45.43.44 Tryptophan.09.09.11.12.12 Growth Performance 生长性能 Daily gain, kg.69.57.42.66.59 Daily feed, kg1.951.761.471.821.76 Gain/feed.35.35.29.36.34 Bellaver (1989) Synthetic Amino Acids 合成氨基酸 Rapid advances occurring in production technology particularly through the use of genetically modified microbes. 生产技术发展迅速，尤其通过遗传改良的微生物生产合成氨基酸 Most are made by microbial fermentation but chemical synthesis of intermediate products may be involved 多数由微生物发酵生产，但也可能通过中间产品进行化学合成 Commercially of interest today:养猪生产中可用 L-lysine, DL-methionine, L-tryptophan, L-threonine L赖氨酸，DL蛋氨酸，L色氨酸，L苏氨酸 The rest are expensive and likely to remain so. 其余氨基酸很昂贵，可能持续如此 Growth of Pigs (9.0-97.8 kg) Fed Reduced-Protein Diets with Lysine, Tryptophan and Threonine 9. 0-97.8 kg 阶段猪饲喂低蛋白日粮添加赖氨酸， 色氨酸和苏氨酸的生长性能 Item 16, 13, 12% CP 14, 11.5, 11% CP + Lysine 14, 11.5, 11% CP Daily gain, kg.75.75.64 Daily feed, kg2.542.532.43 Gain/feed.29.29.26 Easter and Baker (1980) Effect of Lysine Addition to a Diet Formulate with Cottonseed Meal and Sorghum 以棉籽粕和高粱配制的日粮添加赖氨酸的效果 Item Soybean meal standard Cottonseed Meal + Lysine .60.70.80 No.10191919 Initial wt., kgs18.318.518.118.6 Daily gain, kg.235.213.206.230 Daily feed, kg.85.65.69.79 Gain/feed2.352.132.062.30 Knabe et al., 1980 Chemical Score of a 11% and 15.5% Crude Protein, Corn-Soybean Meal Diet for the 50-80 kg Pig Amino acid CP in DietRequire ment % provided by diet 11%15.5%11%15.5% Lysine.45.77.6668.18116.67 Tryptophan.10.17.1283.33141.67 Threonine.40.58.4393.02134.88 Isoleucine.41.63.37110.81170.27 Met + Cys.43.55.39110.26141.03 Leucine1.171.48.67174.63220.90 Histidine.30.42.21142.86200.00 Valine.52.74.45115.56164.44 Phe + Tyr.891.30.63141.27206.35 Arginine.58.94.24241.67391.67 Based on the NRC (1998) Growth of Pigs Fed Reduced-Protein Diets with Lysine 9.097.8 kg 阶段猪饲喂低蛋白日粮添加赖氨酸，色氨酸和苏氨酸的效果 Item Normal C.P. Reduced C.P. Reduced CP +Lys,Thr, Trp Daily gain, kg.70.62.71 Daily feed, kg1.851.891.92 Gain/feed.38.33.37 Dressing %75.9075.9376.83 Liver wt., kg1.661.531.56 Leaf fat,kg1.391.791.48 Backfat, cm3.163.813.33 Loineye, cm231.3526.6531.81 Muscle %51.4347.8650.33 Kerr (1987) Effect of Amino Acid Supplementation on Heat Production by Growing Pigs 添加氨基酸对生长猪产热的影响 Diet Heat Production Kcal/day/kg.75 16% CP corn-soybean meal140 12% CP corn-soybean meal131 12% CP corn-soybean meal + lysine, threonine & tryptophan 132 Kerr (1987) 玉米豆粕日粮，蛋白水平 16 玉米豆粕日粮，蛋白水平 12 12 的玉米豆粕日粮 赖氨酸，苏氨酸和色 氨酸 Effect of Reduced-Protein Diets with Lysine, Tryptophan and Threonine on N Excretion 低蛋白日粮添加赖氨酸，色氨酸和苏氨酸对氮排出的影响 Item Normal C.P. Reduced C.P. Reduced CP +Lys,Thr, Trp N Intake, g/d26.1818.7419.72 Fecal N, g/d4.073.643.72 Urinary N, g/d4.794.322.54 Kerr et al. (1995) Effect of Amino Acid Addition to a Fortified Sorghum Gestation Diet 补充了维生素预混料的高粱妊娠日粮中添加氨基酸的效果 Diet Nitrogen retained, g/d Sorghum-soybean meal16.72 Sorghum12.60 Sorghum + Lysine15.76 Sorghum + Threonine13.24 Sorghum + Lysine + Threonine Cuaron and Easter (1982) 氮储留 Differential Absorption of Intact-protein and Unbound Lysine 完整蛋白质与非结合赖氨酸的区别吸收 全部完整蛋白质 合成赖氨酸 Effect of Meal Frequency on the Response of Pigs to Supplemental Lysine 饲喂次数对猪的添加赖氨酸生长反应的影响 Meals/dayLysine g/day Gain g/day Feed/ gain 104353.09 124912.75 604463.01 625302.57 645532.45 Batterham and ONeill (1978) Meal Frequency and Synthetic Amino Acids 饲喂次数与合成氨基酸 Assume that ad libitum-fed pigs eat frequent meals and blood levels are constant. 假定自由采食的猪采食频繁，血液氨基酸水平保持稳定 A concern in animals fed only once each day, eg., gestating sows. 关注那些每天只饲喂一次的猪，如妊娠母猪 Nutrient Requirements for Swine 猪的营养需要量 Amino acid Liveweight, 体重， kg 1-55-1010-2020-5050-110 Arginine Histidine Isoleucine Leucine Lysine Methionine + Cystine Phe + Tyr 苯丙酪 Threonine 苏氨酸 Tryptophan 色氨酸 Valine 缬氨酸 NRC (1988)The only classification criterion is weight. Gender, genotype and environment are ignored 仅以体重为分级标准，性别，遗传型和环境因素忽略不计 氨基酸 精氨酸 组氨酸 异亮氨酸 亮氨酸 赖氨酸 Fact about Requirements 关于需要量 Expressed as a percent of the diet 以占日粮百分比形式表示 Decrease with age 随年龄增加而降低 Increase with increasing caloric density of diet 随日粮热量浓度增加而增加 Are greater for gilts than barrows 母猪的需要量大于阉公猪的需要量 Are greater for more muscular animals 肌肉型猪的需要量更大 Are greater for maximal leanness than maximal gain 达到最大瘦肉量的需要量比获得最大增重所需更大 Are affected by the protein level in the diet 受日粮蛋白水平影响 Effect of Dietary Lysine on Growth Performance and Carcass Traits of Late Finishing Gilts 日粮赖氨酸水 平对肥育后期小母猪生长性能和胴体性状的影响 Digestible Lysine, % .35.43.50.58.65 Gain, g/d834906993969976 Feed, g/d3215 3341334332413218 Gain/feed260271297299303 Lean gain, g/d307332354365366 Backfat, mm22.121.020.021.020.4 L. dorsi, cm211.59.59.18.18.3 Hahn (1994) Effect of Dietary Lysine on Growth Performance and Carcass Traits of Late Finishing Barrows 日粮赖氨酸水平对肥育后期阉公猪生长性能和胴体性状的影响 Digestible Lysine, % .35.43.50.58.65 Gain, g/d914965111810461057 Feed, g/d3547 3601394536853749 Gain/feed255267284282281 Lean gain, g/d276296344347337 Backfat, mm29.826.830.724.125.1 L. dorsi, cm238.337.537.141.140.0 Hahn (1994) 可消化赖氨酸 Lysine Requirement for Late Finishing Pigs 肥育后期猪的赖氨酸需要量 Breakpoints: 转折点 Barrow = .56% lysine 阉公猪 Gilt = .64% lysine 后备母猪 Hahn, 1994 Lysine Requirement for Late Finishing Pigs 肥育后期猪的赖氨酸需要量 Breakpoints: 转折点 Barrow = . 57% lysine Gilt = .64% lysine Hahn, 1994 Performance and Carcass Composition of Pigs Housed Two per Pen and Fed Two Protein Regimes in Early & Late Finishing 肥育早期和后期，每圈两头，喂以 两种蛋白水平日粮猪的生长性能和胴体组成 SexBarrows 阉公猪Gilts 小母猪 Crude protein, %14.5/13.517.0 % 14.5/13.5 17.0 % Daily gain, g104310331003998 Daily feed, g3437332230363143 Gain/feed304312332318 Lean gain, g/d337336365356 Carcass yield, %74.974.673.974.0 Loin eye, cm237.437.537.938.4 10th rib backfat, mm26.826.524.022.5 Hahn (1994) 性别 粗蛋白 日增重 日采食量 增重饲料比 瘦肉增加量 胴体产量 眼肌面积 第十肋背膘 Performance and Carcass Composition of Pigs Housed Nine per Pen and Fed Two Protein Regimes in Early & Late Finishing 肥育早期和后期，每圈九头，喂 以两种蛋白水平日粮猪的生长性能和胴体组成 SexBarrowsGilts Crude protein, %14.5/13.517.0 % 14.5/13.5 17.0 % Daily gain, g 日增重1043928877864 Daily feed, g日采食量3326331828892851 Gain/feed 增重饲料 比 288280303303 Lean gain, g/d 297286309321 Carc. yield,% 胴体产量74.474.374.474.0 Loin eye, cm2 眼肌面积 37.536.242.343.3 10th rib backfat, mm 28.930.323.721.6 Hahn (1994) 瘦肉增加量 Using Ideal Protein to Estimate Requirements for Amino Acids 利用理想蛋白质估计氨基酸需要量 1. Conduct an experiment to determine the requirement 进行试验确定需要量 Amino Acid Concentrations 氨基酸浓度 Response (gain, lean growth etc) 反应水平（增重，瘦肉生长等） Using Ideal Protein to Estimate Requirements for Amino Acids 利用理想蛋白质估计氨基酸需要量 Amino acid Ideal ratio (% Lysine) Requirement (Lysine x percent) Lysine 赖氨酸100.75 x 1.00 = .75 Arginine 精氨酸36.75 x .36 = .27 Histidine 组氨酸32.75 x .32 = .24 Tryptophan 色氨酸19 Isoleucine 异亮氨酸60 Leucine 亮氨酸100 Valine 缬氨酸68 Phenylalanine + tyrosine 95 Methionine + Cystine65 Threonine67 氨基酸 苯丙酪氨酸 蛋胱氨酸 苏氨酸 需要量 Effect of Energy Level and Lysine:Energy Ratio on Piglet Growth (0-14 days postweaning)日粮能量水平以及赖氨酸与能量比对仔猪生长的 影响（断奶后 014 天阶段） Lys:DE (g/Mcal) DE (Mcal/kg) 3.173.343.51 3.04450455464 3.47461492491 3.91487517501 4.37488490470 Nam and Aherne (1994) Maximum gain achieved at 3.41 Mcal/kg energy density and 3.07 g Lys/Mcal dietary energy 当日粮能量浓度为 3.41 Mcal/Kg， 赖氨酸能量比为 3.07 g Lys/ Mcal 日粮能量时，获得最大增重。 Deductive Requirements 推定的需要量 Based on first principlegs: 以第一条原则为基础 IPR = ACef + MTeff Where: 其中： -IPR = daily ideal protein requirement 理想蛋白质的日需要量 -ACeff = daily protein accretion corrected for efficiency of utilization of dietary protein for accretion 根据日粮蛋白质的沉积效率进行校正后的蛋白质日增加量 -MTeff = daily protein need for maintenance corrected for the efficiency of utilization of dietary protein for maintenance 根据日粮蛋白质的维持效率进行校正后的每日蛋白质维持需要量 Mathematical models can be constructed, using relationships based on first principles, to estimate requirements for pigs under specific circumstances 利用第一条原则中的关系，可建立数学模型，估计猪在 特定条件下的需要