Feed-grade amino acid use in the United States: The synergetic inclusion history with linear programming

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1 2013 Poultry Science Association, Inc. Feed-grade amino acid use in the United States: The synergetic inclusion history with linear programming M. T. Kidd,* 1 P. B. Tillman, P. W. Waldroup,* and W. Holder * Center of Excellence for Poultry Science, Department of Poultry Science, University of Arkansas, Fayetteville 72701; Poultry Technical Nutrition Services LLC, Buford, GA 30518; and Creative Formulation Concepts LLC, Annapolis, MD Primary Audience: Nutritionists, Researchers SUMMARY This review highlights research instrumental in the adoption of feed-grade amino acid inclusion in poultry diets. Attitudes toward industry adoption are discussed by decade, beginning in Synergies between acceptance of least-cost formulation and feed-grade amino acid use are provided. Early acceptance of feed-grade Met was accomplished with formulation examples and resultant bird performance trials, rather than on amino acid requirement research. However, research reports delineating needs of Thr, Ile, and Val are included, as these reports will aid the nutritionist in meeting minimum needs and establishing shadow prices based on current economics. This is useful for fermentation companies to project potential new markets for the branched-chain amino acids. The need for more practical research with the less limiting amino acids to offer cost savings from aggressive feed-grade amino acid use while maintaining bird performance goals is discussed. Key words: amino acid, methionine, lysine, threonine, valine, isoleucine, least-cost feed formulation 2013 J. Appl. Poult. Res. 22 : DESCRIPTION OF PROBLEM Supplemental feed-grade amino acids (AA) have been used in the diets of agricultural animals since the 1950s. Although adoption of the first limiting AA in poultry (Met) was relatively rapid, adoption of the second limiting (Lys) and third limiting (Thr) AA did not occur until the 1970s and 1990s, respectively. References dating back to the 1950s are used herein to highlight key factors that have affected the use of feed-grade AA. High emphasis is placed on AA research in broilers conducted during the past 10 yr, as much of this work is focused on predicting the dietary needs of the branched-chain amino acids (BCAA). Moreover, research with BCAA is paramount to provide insight for the consideration of the fourth limiting AA. Hence, accurate ratios of the BCAA to Lys, coupled with an understanding of minimum nutrient levels of AA less limiting than the BCAA (e.g., Arg, Trp, and possibly Gly), are critical for future advances in the use of feed-grade AA in poultry diets. This review provides the history of research reports 1 Corresponding author: mkidd@uark.edu

2 584 JAPR: Review and computer least cost formulation advances that have led to present day AA use in poultry diets. Hypotheses are provided for future research directions to increase feed-grade AA use and further reduce dietary protein overages. 1950s: THE INTRODUCTION OF LEAST-COST FORMULATION Sixty years ago, many nutritionists believed protein needs could never be replaced by feedgrade AA. Linear programming was first used to formulate a dairy diet in 1951 [1]. Halloran [2] applied the concept to the formulation of layer feeds in California. Thereafter, a group at the Pennsylvania State University Experiment Station led by Hutton [3] carried out an effort in formulating poultry diets. The introduction of both feed formulation and dry Met hydroxy analog calcium offered lower cost diets and resulted in the dietary use of feed-grade Met. The first issue on accepting feed-grade AA in poultry diets arose with linear programming, because many poultry industry nutritionists and university scientists could not afford computers. The article by Hutton et al. [3] on least-cost formulation provided examples of poultry diets that included corn, soybean meal, and a Met source. Because diet cost was $70.95 per 2,000 lbs, and the Met source represented $5.73($2.18 /lb) of total diet cost, few accepted the economic efficacy of including a feed-grade Met source. The second issue arose with the dietary inclusion of feedgrade Met, because reduced protein and AA balance were as foreign as computer formulation. As a result, the Monsanto Chemical Company invested in a computer system and formulated feed as a service to its customers in the United States, with the DuPont Company following their lead shortly afterward. Unfortunately, many poultry nutritionists still felt that diets that used ingredients beyond corn and soybean meal would have altered nutrients and not been efficacious. Although Hutton et al. [3] provided the results of least-cost formulation, running linear algorithms required large mainframe computers. Because these mainframe computers often cost $1 million or more, by the end of the 1950s only a few allied industry companies and universities were able to invest in computers. 1960s: INDUSTRY ACCEPTANCE AND USE OF LEAST-COST FORMULATION Early efforts were made to bring linear programming to the poultry industry in the late 1950s by Halloran and Schultz [4], but the usage was limited as nutritionists were not trained in linear programming and had little or no knowledge of the use of computers. The acceptance of the use of linear programming by the poultry industry was greatly aided by R. Borgland at Oklahoma State University [5], by L. Potter et al. at the University of Connecticut [6], and later, at Virginia Polytechnic Institute and State University [7]. Acceptance was also advanced by the publication of a series of nutrient specifications for linear programming of broiler diets by G. Combs and J. Nicholson at the University of Maryland [8]. Bray and Garlich [9] were the first to document large responses to AA in low-protein diets. They supplemented dl-met, l-lys-hcl, dl- Trp, dl-ile, and dl-val to a 9% CP, corn- and soybean-meal-based diet, and documented improved egg production and nitrogen retention to levels similar to birds fed a diet higher in CP. They attributed their AA responses, and the lack of responses in previous research [10], to the extent to which CP was reduced. Subsequent research in the 1960s was conducted to determine the efficacy of feed-grade Met and Lys sources. Harms et al. [11] conducted studies in laying hens fed corn and soybean meal diets and found an improvement in laying performance from Met hydroxy analog calcium in the presence of reduced dietary protein. Additional research from the same laboratory [12] (with Hy-Line pullets) demonstrated the nutrient limitation of both Met and Lys by supplementing lower protein corn-soybean-based diets with Met hydroxyl analog calcium and l-lys HCl. Industry acceptance of least-cost formulation continued to be met with discouragement because few poultry companies could purchase computers with enough mathematical power to run linear algorithms. In 1965, Computone Systems Inc. of Atlanta, Georgia, launched a provision for least-cost formulation timeshare service for a monthly fee plus the long distance fee for formulation run time. Because algo-

3 Kidd et al.: AMINO ACID USE rithm run time typically exceeded 5 min, long distance telephone charges prevented widespread adaptation of the formulation timeshare service. 1970s AND 1980s: MAINFRAME SYSTEMS TO PERSONAL DOS SYSTEMS As Computone runtime was decreased from 5 to 1 min in the early 1970s, industry adoption of this technology increased. But widespread acceptance of least-cost formulation required more technological improvements. In the 1970s and 1980s, acceptance or adoption of linear programming flourished as technology progressed from remote timesharing systems to in-house formulation platforms and ultimately to the desktop computer. One of the earlier platforms (SciData Inc., Atlanta, GA) that competed with the timeshare system was the turnkey leastcost formulation system that was equipped with a display screen, removable hard drive, and high-speed dot matrix printing. In 1975, the NRC Corporation (Dayton, OH) initiated the Feed Information System to aid company mainframes with more accurate ingredient specifications. Although over 50 Feed Information Systems were sold, the NRC Corporation removed the service in The 1970s gave rise to microcomputers (e.g., Apple and Tandy), but lack of memory to run mathematical algorithms still prevented widespread use by poultry companies. The breakthrough in technology that brought about widespread adoption of feed formulation systems on personal computers was in 1983 when IBM launched a personal computer with the power to compete with mainframes. Rather than mainframe formulation submission with next-day pick up, nutritionists could execute what if exercises with ingredients with a nearly instantaneous turn-around-time. Although research allowed for more accurate formulation levels of synthetic Met sources and crystalline Lys sources, their use did not vary greatly. Hence, many nutritionists only allowed 1 lb of feed-grade Lys to enter formulation, which, by default, established a minimum CP level and removed the ability to evaluate the efficacy of the next limiting AA, which primarily is Thr. 1990s: l-threonine AND NETWORKS TO WINDOWS 585 With the l-lys inclusion constraint previously mentioned, sometimes as low as 400 to 500 g/t, nutritionists could solve for TSAA and Lys, but other AA were still in excess. Research throughout the 1990s provided Thr estimates [13] that aided nutritionists in dispelling the feed-grade l-lys restriction while more closely meeting the birds needs for essential AA. Although l-thr use in formulation was not linked to computer software advances per se, the improved understanding of ingredient composition, nutrient ratio requirements, and nutrient equations brought about by computer networks allowed flexibility in formulation. Allied industry expanded on this knowledge by circulating ingredient AA composition and digestibility charts. This was further increased in the mid-1990s, as DOS-based systems moved to Windows-based software. The 1990s was an important decade for Thr because it represents the third limiting AA in most commercial poultry feeds, and little prior research existed in growing and finishing broilers (Table 1). However, increased commercial production of l-thr in the 1980s created interest, and some laboratories conducted studies to determine the broiler s dietary requirement for this essential AA. Much of the Thr research conducted focused on needs of chicks [14 19]. The limiting factors for commercial l-thr use in the early 1990s were price and lack of requirement estimates in the growing and finishing periods. The latter limitation required research, as the Thr need for bird maintenance relative to Lys is substantial. Four laboratories in the 1990s published Thr needs between 20 and 42 d of age and generated estimates of digestible Thr between 0.60 and 0.61% of diet [20 23]. In older broilers (42 56 d of age), Thr estimates vary. Webel et al. [20] determined that the digestible Thr need for 42- to 56-d-old broilers was 0.52%, whereas Dozier et al. [24] and Kidd et al. [25] estimated digestible Thr needs of 0.59 and 0.58%, respectively. The later estimates [24, 25] may be higher than that of Webel et al. [20] because trials were carried out in floor pen environments with built-up litter. Additional requirement estimates for Thr are presented in Table 1 [26, 27].

4 586 JAPR: Review Table 1. Research on digestible Thr requirement in male broilers Day of age Thr 1 (%) Strain Reference Ross TP-16 Corzo et al. [26] Numerous 2 Leclercq [21] Ross Hubbard Webel et al. [20] Peterson Arbor Acres Penz et al. [22] Ross TP-16 Everett et al. [27] Ross 308 Kidd and Kerr [23] Ross Hubbard Webel et al. [20] Ross Hubbard Kidd et al. [25] Ross 308 Dozier et al. [24] 1 Average of BW gain and feed conversion estimates. 2 Mathematical model predictions from selected published research reports. Wu [28] described the catabolism of AA in the intestinal mucosa. It was hypothesized that 30 to 50% of Arg, Pro, Ile, Val, Leu, Met, Lys, Phe, Thr, Gly, and Ser are used for enzyme and tissue needs and are not available to extraintestinal tissues. Regarding Thr, Bertolo et al. [29] indicated that piglets fed intragastrically have a Thr requirement 45% less than piglets fed orally, indicating the importance of Thr in intestinal functionality. Threonine is a key AA for mucin needs, especially in reduced-cp diets. Hence, reduced performance in broilers fed low- CP diets may be a result of a need for mucin rather than a direct function of AA digestibility or availability. Research by Kidd et al. [30] and Corzo et al. [31] evaluated dose titrations of dietary Thr in birds from 42 to 56 d of age placed in pens with new or old litter. Although both studies predicted digestible Thr needs of birds raised on old litter of 0.61 and 0.65%, respectively, it was shown that birds raised in the pens with old litter had Thr needs approximately 4% higher than those in pens with clean litter. Therefore, it must be pointed out that environment and litter type should be taken into consideration for Thr research trials conducted with the goal of industry applicability. How much does the dietary Thr requirement vary in birds differing in intestinal environments? Proteins in the intestinal mucus layer, an important nonimmune intestinal barrier, have been shown to contain 30% Thr [32]. Azzam et al. [33] provided Babcock Brown laying hens Thr in excess of published standards [34] and noted increases in jejuna and ileal mucin-2 in RNA expression. Increases in ileal IgA were also noted with Thr levels in excess of needs for egg production. The extent to which Thr needs should be increased in birds (fed all-vegetablebased diets or with environmentally altered intestinal microflora) should be researched further for accurate Thr predictions that can be used in industry feed formulation. Moreover, Thr estimates that accurately reflect needs of birds in practice will allow for optimization of the fourth limiting AA in broiler diets, which includes the following candidates: Val, Ile, Trp, or Arg [35]. However, it is anticipated that the fourth limiting AA will vary based on the ingredients used in a formulation [35]. THE 2000s: THE BCAA AND THE DEATH OF DOS In the 2000s, virtually all personal systems switched from DOS to Windows, as formulation companies rewrote software for Windows-based applications. The resultant movement ended a 30-yr reign of DOS-based system platforms. In an effort to maintain adequate levels of a pool of AA nitrogen for nonessential de novo synthesis, the past few years have given rise to numerous reports on the dietary needs for the essential BCAA, Val, Ile, and Leu. Because Leu is considered to be least likely limiting in practical diets due to its high content in corn and soybean meal, the bulk of the emphasis has been placed on Val and Ile. A review paper by Tillman [36] presented recently published reports on Val and Ile requirement estimates for broilers, and a summary from that paper is presented in Tables 2 and 3, respectively. Research with feed-grade l-val has increased, as it is completely available

5 Kidd et al.: AMINO ACID USE 587 Table 2. Research on digestible Val requirements in male broilers 1 Day of age Val 2 (%) Strain Reference Ross 308 Corzo et al. [47] Cobb 500 Goodgame et al. [48] Cobb 500 Campos et al. [46] Ross 308 Corzo et al. [47] Cobb 500 Goodgame et al. [48] Ross 508 Thornton et al. [49] Ross 708 Corzo et al. [39] Cobb 500 Campos et al. [46] Ross 308 Corzo et al. [47] Ross 308 Corzo et al. [45] 1 Adapted with permission from Tillman [36]. 2 Average of BW gain and feed conversion estimates. to the bird [37] and became commercially available in Corzo et al. [38] showed that l-val could be successfully used at an inclusion level above 0.05%, in practical broiler diets, which also contained dl-met, l-lys HCl, and l-thr. Several published papers [39 41] have noted in all vegetable-based broiler diets, with corn and wheat as the primary grain, Val is the fourth limiting AA. In broiler diets, which contain animal byproducts, research has suggested the existence of a colimitation between Val and Ile [40 42]. From these papers, it seems as though diets containing meat and bone meal tend to be fourth limiting in Val, whereas those containing poultry by-product meal are more likely to be fourth limiting in Ile. However, in a paper by Corzo et al. [43], it was suggested that Ile was fourth limiting in a meat and bone meal-based diet. As such, it is clear that due to the colimitation between these 2 BCAA, minor changes in the minimum constraint of either, within feed formulation software, can change the dynamics and thus the order of limitation. In reality, and because of the colimitation issue, to fully optimize broiler performance, such as BW gain and feed conversion, levels for both digestible Val and digestible Ile need to be near their requirement. Corzo et al. [41, 44, 45] has shown the requirement for both AA to be higher than NRC [34] recommendations. Additional papers that have provided insight in the minimum Val level needed in formulation are presented in Table 3 [46 49]. An observation of particular note across several publications is the response in breast meat weight or yield from an increased or optimal Ile level [41, 42, 50 55]. Therefore, in markets where white meat is the primary goal of broiler production, emphasis should not only be placed to ensure Met, Lys, and Thr requirements are met, but also that levels for digestible Val and, perhaps especially, digestible Ile are met as well. If the concept of ideal protein is used in formu- Table 3. Research on digestible isoleucine requirements in male broilers 1 Day of age Ile 2 (%) Strain Reference Cobb 500 Helmbrecht et al. [54] Cobb 500 Campos et al. [52] Ross 308 Kidd et al. [51] Ross Hubbard Kidd et al. [50] Cobb 500 Campos et al. [52] Ross 708 Mejia et al. [35] Ross 308 Kidd et al. [51] Cobb 500 Helmbrecht et al. [54] Ross 308 Kidd et al. [51] 1 Adapted with permission from Tillman [36]. 2 Average of BW gain and feed conversion estimates.

6 588 JAPR: Review lation, setting appropriate ratios for Ile and Val should support adequate tissue accretion based on available data. In the near future it may become common practice for commercial broiler diets to contain l-val and l-ile, in addition to Met, Lys, and Thr sources. As more supplemental AA enter formulation, a concomitant decrease in soybean meal occurs. In this scenario, and in particular all vegetable diets, Gly seems to be semiessential deeming a Gly + Ser minimum to be set in least cost formulation. Chick Gly + Ser needs a range from just over 2 [56] to almost 2.5% [57]. This effect does not seem to necessitate a nonessential nitrogen need, as the efficiency of Gly + Ser in low-cp diets in chicks was not spared by dietary addition of l-glu or nitrogen [56]. In addition to protein pool supply, Gly is a precursor of glutathionine peroxidase, nucleic acids, creatine, heme, bile, and it serves as a methyl source [58]. Moreover, each molecule of uric acid contains 1 molecule of Gly, and under some circumstances Gly is considered essential. To effectively reduce CP with the commercially available AA, Gly interrelationship to Thr, betaine, and enzymes warrants attention. CONCLUSIONS AND APPLICATIONS 1. As each synthetic AA has reached the marketplace, there has been a period of uncertainty toward its full adoption within practical formulation. 2. Computer advances that decreased runtime of linear algorithms, coupled with linear programming formulation software advances, were instrumental in adoption of Met source feed-grade inclusion. 3. Commercial adoption of Met, Lys, and Thr sources in poultry diets occurred in the 1960s, 1970s, and 1990s, respectively. 4. l-valine and l-ile may see commercialization within a decade, as high ingredient prices and reduced global resources increase the demand for food security. 5. The inclusion of each subsequent AA allows for formulation closer to the bird s requirement, thereby reducing AA overages and leading to a reduction in bird nitrogen excretion. REFERENCES AND NOTES 1. Waugh, F. V The minimum-cost dairy feed: An application of linear programming. J. Farm Econ. 33: Halloran, H. R Personal communication dated Jan. 23, Halloran Research Farm, Modesto CA. 3. Hutton, R. F., G. A. King, and R. V. Boucher A least-cost broiler feed formula method of derivation. USDA- Agricultural Research Service Pennsylvania Agriculture Experiment Station Production Research Report Number 20. Washington, DC. 4. Halloran, H.R., and F.T. Schulz Electronic feed formulation service. Western Feed and Seed. Vol. 14(1): Jan. 5. Berglund, R Feed formulation in the space age. Feedstuffs. 30:28, Potter, L. M., J. W. Mamer, H. C. Lampe, and E. Hoffman Use of high speed electronic computer in formulation of poultry diets. Poult. Sci. 39: Potter, L.M., J.W. Mamer, H.C. Lampe, and E. Hoffman Linear programming and its use in the feed manufacturing industry. Feedstuffs 34:18 19, Combs, G.F., and J.L. Nicholson Testing energy, amino acid and protein level specifications for linear programming for broiler rations. Feedstuffs 36:17 21, Bray, D. J., and J. D. Garlich Studies with corn-soya laying diets: 1. Amino acid supplementation of low protein diets. Poult. Sci. 39: Thornton, P. A., L. G. Blaylock, and R. E. Moreng Protein level as a factor in egg production. Poult. Sci. 36: Harms, R. H., C. R. Douglas, and P. W. Waldroup Methionine supplementation of laying hen diets. Poult. Sci. 41: Harms, R. H., and P. W. Waldroup Methionine hydroxy analogue and lysine supplementation of low protein laying diets. Br. Poult. Sci. 4: Kidd, M. T Nutritional considerations concerning threonine in boilers. World s Poult. Sci. J. 56: Thomas, O. P., P. V. Twining, Jr., E. H. Bossard, J. L. Nicholson, and M. Rubin Broiler chick studies with threonine and lysine. Page 44 in Proc. Maryland Nutr. Conf., Baltimore, MD. 15. Thomas, O. P., A. I. Zuckerman, M. Farran, and C. B. Tamplin Updated amino acid requirements of broilers. Page 79 in Proc. Maryland Nutr. Conf., Baltimore, MD. 16. Thomas, O. P., M. Farran, C. B. Tamplin, and A. L. Zuckerman Broiler starter studies. I. The threonine requirements of male and female broiler chicks. II. The body composition of males fed varying levels of protein and energy. Page 38 in Proc. Maryland Nutr. Conf., Baltimore, MD. 17. Uzu, G Threonine requirements for broilers. AEC Information Poultry 252:03600 Commentry, France. 18. Smith, N. K. Jr., and P. W. Waldroup Investigations of threonine requirements of broiler chicks fed di-

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8 590 JAPR: Review Broiler responses to reduced-protein diets supplemented with valine, isoleucine, glycine, and glutamic acid. J. Appl. Poult. Sci. 19: Helmbrecht, A., F. de Castro Tavernari, H. S. Rostagno, L. F. Teixeira Albino, and A. Lemme Optimal digestible isoleucine to lysine ratios in starter and finisher broilers. Proc. 13th Eur. Poult. Conf. Poster Session I: August in Tours, France. 55. Mejia, L., C. D. Zumwalt, E. J. Kim, P. B. Tillman, and A. Corzo Digestible isoleucine-to-lysine ratio effects in diets for broilers from 4 to 6 weeks posthatch. J. Appl. Poult. Res. 20: Waguespack, A. M., S. Powell, T. D. Bidner, and L. L. Southern The glycine plus serine requirement of broiler chicks fed low-crude protein, corn-soybean meal diets. J. Appl. Poult. Res. 18: Dean, D. W., T. D. Bidner, and L. L. Southern Glycine supplementation to low protein, amino acid-supplemented diets supports optimal performance of broiler chicks. Poult. Sci. 85: Reeds, P. J., and H. J. Mersmann Protein and energy requirements of animals treated with beta-adrenergic agonists: A discussion. J. Anim. Sci. 69: