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带图表的英文原版文章已上传到我的网盘。
KristjanBregendahl在Degussa的09年1月份的AMINOnews上发表了最新的蛋鸡氨基酸模型的综述,在下搜索到了这篇08年的文章以飨网友,有兴趣的也可以和Degussa联系索要一下这份资料。结合起来看效果更好的。个人认为这个实验对蛋鸡理想氨基酸模型目前来看更系统更有应用价值。
Ideal Amino Acid Profile for 28-to-34-Week-Old Laying Hens
Kristjan Bregendahl,1 assistant professor;
Stacey Roberts, graduate research assistant;
Brian Kerr, research leader, USDA/ARS;
Dirk Hoehler, director of technical services, Evonik Degusssa Corporation
Summary and Implications
Theideal amino acid (AA) profile employs the concept that, whereasabsolute AA requirements change due to genetic or environmentalfactors, the ratios among them are only slightly affected. Thus, oncethe ideal AA profile has been determined, the requirement for a singleAA (i.e., lysine) can be determined experimentally for a given fieldsituation and the requirements for all the other AA calculated from theideal ratios. Seven separate experiments were conducted with layinghens to determine the ideal ratio of arginine, isoleucine, methionine,methionine+cystine, threonine, tryptophan, and valine relative tolysine for maximal egg mass. The assays were conducted simultaneouslyusing the same basal diet to which crystalline AA were added to createthe graded level of the respective assay AA and to ensure that theassayed AA was first limiting. Hens were fed the assay diets from 26 to34 weeks of age, with the first 2 weeks considered a depletion period.Egg production was recorded daily and egg weight was determined weeklyon eggs collected over 48 hours; egg mass was calculated as eggproduction × egg weight. The requirement for each AA was determinedusing the broken-line regression method. Consumption of arginine didnot affect egg mass, thus an ideal arginine:lysine ratio could not bedetermined. The ideal AA ratio for maximum egg mass for28-to-34-week-old laying hens was isoleucine 79%, methionine 47%,methionine+cystine 94%, threonine 77%, tryptophan 22%, and valine 93%on a true digestible basis relative to lysine.
Introduction
Aminoacid requirements for laying hens are published by the NationalResearch Council.2 However, the experiments upon which theserequirements are based are dated and do not account for the geneticprogress of laying hens in the last 12 or more years. Amino acidrequirements have been reported since the publication of the National
ResearchCouncil requirements. However, these experiments have been conductedfor 1 AA at a time, performed under different experimental conditionsand with different basal diets, genetic lines of hens, feed consumptionrates, dietary energy contents, ambient temperature, cage space, andages of laying hens, all of which influence the AA requirements.
Becausemultiple factors affect AA requirements, requirements determined underexperimental conditions may not be applicable under field conditions.The solution to obtaining reliable AA requirements is therefore not todetermine the AA requirements, but rather to determine the ideal AAprofile for laying hens. The ideal AA profile employs the concept that,while AA requirements change drastically due to genetic orenvironmental factors, the ratio among them is only slightly affected.Thus, once the ideal AA profile has been determined, the requirementfor a single AA (e.g., lysine) can be determined experimentally for agiven field situation and the requirement for all the other AAcalculated. Such an approach has been adopted with success by the swineindustry and is finding use in the broiler industry as well.
Theobjective of Experiment 1 was to investigate responses of laying hens,28 to 34 weeks of age, to graded dietary inclusions of the essential AAarginine, isoleucine, lysine, methionine, threonine, tryptophan, andvaline, in order to determine the ideal AA ratios of the assayed AArelative to lysine. In Experiment 2, the objective was to confirm thelysine, methionine, and methionine+cystine requirements (and,therefore, the ideal methionine:lysine and methionine+cystine:lysineratios) determined in Experiment 1.
Material and Methods
Housing and Management
Atotal of 1,008 white single-comb Leghorn–type hens (Hy-Line W-36), 26weeks of age, were housed 2 per cage (619 cm2/hen) in wire-bottomedcages (Chore-Time, Milford, IN), each equipped with a plasticself-feeder and a nipple drinker. The photoperiod was 16 h of light and8 h of darkness and the hens had free access to feed and water at alltimes. Prior to Experiment 1 and between Experiments 1 and 2, the henswere fed and managed in accordance with the Hy-Line W-36 CommercialManagement Guide. All procedures relating to the use of live animalswere approved by the Iowa State University Institutional Animal Careand Use Committee.
Dietary Treatments
Abasal diet was formulated using corn, soybean meal, and meat and bonemeal to meet or exceed all nutrient requirements, except amino acids.In Experiment 1, the basal diet was mixed in 2 separate 2,722-kgbatches in a horizontal mixer at a commercial feed mill (Kent Feeds,Altoona, IA) and bagged in 22.6-kg bags according to batch number. InExperiment 2, a basal diet was mixed in a vertical mixer in 3 separate500-kg batches at the Iowa State University Poultry Science ResearchCenter. Representative samples of the basal-diet batches were pooledwithin experiment and analyzed for AA content by ion-exchangechromatography and for true AA digestibility by the cecectomizedrooster assay. The crystalline AA added to the basal diet were assumedto be 100% true digestible.
The 35 assay diets in Experiment 1 wereformulated with equal parts of each of the 2 basal-diet batches plus amixture of cornstarch, K2CO3 to maintain a similar dietary electrolytebalance among all diets, and crystalline AA to create 5 equally spacedgraded inclusions of each of the 7 assayed AA, such that diet 3provided the assayed AA at the estimated requirement (Table 1). InExperiment 2, only the responses to lysine and methionine weredetermined; thus, there were 10 assay diets formulated with equal partsof each of the 3 basal-diet batches as described for Experiment 1(Table 1). Crystalline AA, other than the one assayed, were added toall diets to assure that the assayed AA was first-limiting in any givenassay diet.
Data Collection
Henswere offered free access to the assay diets from 26 to 34 weeks of age(Experiment 1) or from 50 to 58 weeks of age (Experiment 2), with thefirst 2 weeks of each experiment considered a depletion period. Thus,only data from the last 6 weeks of the experiments were used in thestatistical analyses.
Egg production was recorded daily and feedconsumption (determined as feed disappearance) was measured weeklythroughout the 8-week-long experiments. Consumption of the assay AA(mg/day) was calculated from the mean daily feed consumption (g/day)over the last 6 weeks of each experiment and the dietary truedigestible AA content (%). This latter content was calculated from theanalyzed total AA content of the basal diet multiplied by the analyzeddigestibility coefficient plus the inclusion of crystalline AA. Onceevery week, eggs collected over a 48-hour period were weighed and theegg mass calculated by multiplying the week’s egg-production rate bythe egg weight.
Statistical Analyses
Therequirement for each assayed AA was determined in a randomized completeblock design with 5 dietary treatments (i.e., 5 levels of the assayedAA) and 12 blocks.
The cage location within the barn served asthe blocking criterion and the experimental unit was 1 cage containing2 hens. The requirements for digestible AA were calculated with thesingle-slope broken-line regression model with the consumption of theassayed AA (mg/day) as the independent variable. Block was not includedin the broken-line regression model. Feed consumption data wereanalyzed by analysis of variance (ANOVA) with block and dietarytreatment as the independent variables; treatment effects wereseparated using linear, quadratic, and cubic orthogonal polynomialcontrasts.
Results
Theresponses to consumption of arginine, isoleucine, lysine, methionine,methionine+cystine, threonine, tryptophan, and valine in Experiment 1are shown in Figure 1. Hens fed the 5 arginine assay diets consumedbetween 574 and 843 mg/day of true digestible arginine, yet there wereno responses to consumption of arginine. The responses to consumptionof lysine, methionine, and methionine+cystine in Experiment 2 are shownin Figure 2. Hens fed the graded levels of AA generally responded byincreasing the feed consumption in a linear or curvilinear matter(Table 2). The requirements for true digestible AA for maximal eggproduction, egg weight, and egg mass, calculated using the broken-lineregression method are shown in Table 3, whereas the ideal AA profilefor maximal egg mass are shown in Table 4.
Discussion
TheAA requirements, used to calculate the ideal AA profile, weredetermined with the broken-line regression model. This method isconsidered the best for obtaining the ideal ratios among AA, whereascurvilinear models, such as exponential or quadratic curve fitting, arebetter suited to establish the AA requirements for optimal performance.Typically, the broken-line regression method results in lower AArequirements than when a non-linear curve fitting is applied to thesame dataset. However, the broken-line regression model has theadvantages of a clearly defined breakpoint (i.e., the requirement) at adietary AA consumption that marginally limits performance, bothnecessary to determine the ideal AA profile. Although the absolute AArequirements (mg/day) are reported herein, they are only valid for theparticular hens in the particular experimental settings in the presentstudy and should not necessarily be used in commercial settings,especially because they were determined using the broken-line method,and not a curvilinear model.
The intent with the experimental designof the current study was to have 2 of the 5 assay diets supply theassayed AA below the estimated requirement, 1 diet supply the assayedAA at the estimated requirement, and 2 diets supply the assayed AAabove the estimated requirement. However,the requirements for lysineand methionine were overestimated in Experiment 1, such that only 1assay diet supplied the assayed AA below the observed requirement. Inother words, only 1 of the 5 assay diets was deficient in the assayedAA, lowering the confidence in the calculated AA requirement needed tocalculate the ideal AA profile. Therefore, the lysine and methioninerequirements were reevaluated in Experiment 2 with the same hens usingthe same methodology as in Experiment 1, albeit with lower dietarycontents of the assayed AA. Consequently, the breakpoints for lysine,methionine, and methionine+cystine were better defined in Experiment 2.Despite the differences in the age of the hens between the 2experiments, the requirements for true digestible lysine, methionine,and methionine+cystine were similar. Accordingly, the idealmethionine:lysine ratios (47 and 52% in Experiments 1 and 2,respectively) and methionine+cystine:lysine ratios (94 and 96% inExperiments 1 and 2, respectively) corresponded fairly well between the2 experiments, indicating that the ratios for methionine andmethionine+cystine determined in Experiment 1 were acceptable. Hence,the ideal AA profile for 28-to-34-week-old laying hens was calculatedfrom the true digestible AA requirement for maximal egg mass fromExperiment 1.
The ideal AA ratio for maximum egg mass for28-to-34-week-old laying hens was isoleucine 79%, methionine 47%,methionine+cystine 94%, threonine 77%, tryptophan 22%, and valine 93%on a true digestible basis relative to lysine. The ideal AA profiledetermined in this study indicated that laying hens need less truedigestible isoleucine and valine and more true digestible methionineand threonine in relation to lysine than that suggested by Coon andZhang3 and that calculated from requirements published by the NationalResearch Council.2 The ideal isoleucine:lysine ratio observed in thepresent study corresponded well with that calculated from AArecommendations by the Dutch Centraal Veevoederbureau.4In addition, thedetermined ideal AA profile agrees well with the profile calculatedfrom AA recommendations suggested by Leeson and Summers5 for32-to-45-week-old hens and is similar to that reported by Jais et al.6with the exception of tryptophan and valine. The idealmethionine:lysine and methionine+cystine:lysine ratios in the presentstudy were higher than those reported by the National ResearchCouncil,2 but agree well with the ratios suggested by the CentraalVeevoederbureau4 and by Leeson and Summers5 for 32-to-45-week-old hens.If the lowest true digestible arginine consumption observed inExperiment 1 (i.e., 574 mg/day) is accepted as meeting or exceeding therequirement of the hen for arginine, the ideal arginine:lysine ratiowas then no higher than 107%, similar to the 101% calculated from theNational Research Council2 arginine and lysine recommendations, andless than the 130% recommended by Coon and Zhang3 (Table 3).
Acknowledgements
Fundingfor the study was provided in part by Evonik Degussa Corporation,Kennesaw, GA, and by the Iowa Egg Council, Urbandale, IA. In-kindcontributions of feed ingredients, pullets, and services were providedby ADM, Des Moines, IA; Evonik Degussa Corporation, Kennesaw, GA; DSMNutrition, Ames, IA; Feed Energy Company, Des Moines, IA; ILCResources, Alden, IA; Kent Feeds, Altoona, IA; Darling International,Des Moines, IA; and Sparboe Farms, Litchfield, MN. The assistanceprovided by personnel in the Bregendahl laboratory and by Jeff Tjelta,Randy Holbrook, Bill Rogers, and Bill Larson at the Iowa StateUniversity Poultry Science Research Center is greatly appreciated.5Leeson, |
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