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Nutrient requirements of poultry publication: History and need for an update
©2014 Poultry Science Association, Inc.
Nutrient requirements of poultry publication: History and need for an update Todd J. Applegate*1 and Roselina Angel† *Department of Animal Sciences, Purdue University, West Lafayette, IN 47907; and †Department of Animal and Avian Sciences, University of Maryland, College Park 20742-0001
SUMMARY The NRC Nutrient Requirements of Poultry has been a benchmark publication for the research, judicial, and regulatory communities domestically and abroad since the first published edition in 1944. The poultry scientific community has looked to this publication for benchmark diet formulation. With extraordinary changes in growth and productive potential of modern poultry strains, as well as changes to body composition and egg output, it follows that nutrient needs have changed beyond what the bird can compensate for with increasing intake per unit of BW. Research publications used for amino acid and phosphorus recommendations in the last NRC are now, at best, from 1991 and at worst from 1947. To our collective credit, the poultry science community has published substantial amounts of data in those areas to warrant an update to the ninth revised edition of the NRC Nutrient Requirements of Poultry. Historically, our perception and definition of a nutrient requirement has changed from first being a requirement, as a percent of a diet, to preventing a nutrient deficiency, to now being a requirement to optimize growth or egg production response per unit of nutrient intake. As economics becomes an increasingly more important driver for the implications of research, the scientific community has begun to embrace the concept of return on investment of nutrient used for compositional growth or egg production. As these concepts take shape, the current edition’s format will have to undergo a substantial creative revision; possibly even embracing the concept of modeling of nutrient responses. Funding for such a revision will require a large financial investment from the NRC, the feed industry, commodity associations, as well as time investment by the scientific community. Key words: poultry, nutrient requirement, National Research Council 2014 J. Appl. Poult. Res. 23:567–575 http://dx.doi.org/10.3382/japr.2014-00980
HISTORY OF THE NRC AND NUTRIENT REQUIREMENT PUBLICATIONS The NRC is the operational arm of the National Academy of Sciences (NAS; established 1
Corresponding author: [email protected]
in 1863), which combined with the National Academy of Engineering and Institute of Medicine in 2013. There are 6 divisions of the NAS, one of which is the Division of Earth and Life Sciences, which is home to 12 boards. The primary board the poultry community would be
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Primary Audience: Poultry Nutritionists, Feed Industry, Government Agencies, Regulatory Committee
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Table 1. History of revisions to NRC Nutrient Requirements of Poultry, Beef, Dairy, and Swine publications (by year) Poultry
1945 1950 1963 1976 1984 1996 2000 2014 (estimated)
familiar with is the Board on Agriculture and Natural Resources. Among this board’s function is to appoint ad hoc committees to develop NRC reports. Notably, the NRC releases approximately one report each working day on issues in science, technology, medicine, social science, and education. The NAS established the NRC in 1916 after a request by President Woodrow Wilson to recruit specialists from the larger scientific and technological communities to participate in and support the work of the NAS. During World War II, the Committee on Animal Nutrition through the NRC was tasked with improving animal nutrition to ensure an adequate food supply for the population during emergency war times. The inception of the Nutrient Requirements of Poultry report from the NRC began with the first 18page edition being published in 1944 [1]. Interestingly, the concept of a requirement was not in place at that time; rather values were listed as nutrient allowances without inclusion of margins of safety. As noted in Table 1, the publication was consistently revised at least every 6 or 7 yr until the 1984, eighth revised edition [2], with the ninth coming 10 yr later [3]. The frequency of updates early in the history of the publication was notable, as new nutrients were being discovered and the relevance of those nutrients for poultry nutrition were established. Inasmuch, the NRC has considered 4 species of upmost importance to consistently update the nutrient requirement publications, namely beef, dairy, poultry, and swine. As updates to the NRC publications were fairly routine over its last 50-yr history, the regulatory and judicial communities
Dairy 1945 1950 1956 1958 1966 1971 1978 1988 2001 2015 or 2016 (estimated)
Swine 1944 1950 1953 1959 1964 1968 1979 1988 1998 2012
in the United States and abroad have used these publications as benchmarks for their guidance. The NRC publications have therefore become very valuable references for regulatory agencies (domestically and internationally), as they are comprehensive evaluations of credible and generally accepted science (for the most part based on published peer-reviewed information) that was current at the time of publication. For example, the US Food and Drug Administration (FDA) makes its scientific determinations to support regulatory processes based on standards that are scientifically sound and consistent; otherwise, the determinations could be viewed as arbitrary and capricious. Traditionally, the FDA uses NRC publications as a standard when making determinations with regard to nutrient recommendations in the evaluation of utility or functionality of substances added to animal feed, as well as during assessment of the safety and toxicity of those substances. The information available in NRC publications regarding toxicity of nutrients or other additives, including tissue levels, maximum tolerable levels, and so on, is regularly used to determine the safety of substances used in animal feed during pre- or postmarket valuations of product safety or the truthfulness of labeling. The US FDA continues to use information in NRC publications as the gold standard when making regulatory determinations. Recognizing the value and merit of NRC publications, the FDA Center for Veterinary Medicine still partially funds relevant NRC publications. However, the FDA also recognizes that some of the information in old NRC publications can be
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1944 1946 1950 1954 1960 1966 1971 1977 1984 1994
Beef
Applegate and Angel: REVISION FOR NUTRIENT REQUIREMENTS somewhat dated; and thus the FDA makes reasonable adjustments and minor deviations from information gathered in NRC publications based on current science and facts when making its determinations.
WHAT HAS CHANGED IN THE UNITED STATES SINCE PUBLICATION OF THE NINTH REVISED VERSION IN 1994?
through the NRC. As mentioned earlier, the primary focus of the initial Committee on Animal Nutrition work was to ensure an adequate food supply, which was accomplished in part through publishing the nutrient requirement publications for livestock and poultry. Currently, this responsibility rests with the Animal Nutrition Program of the Board on Agriculture and Natural Resources (BANR). Today, the major focus of BANR work is centered in 4 areas: (1) environmental quality, refining animal feeding to reduce environmental effects; (2) animal production, improving animal productivity and efficiency; (3) food safety, enhancing the quality and safety of food products derived from animal sources; and (4) animal and human health, ensuring the health and well-being of animals and humans. To help support the Animal Nutrition Program of BANR, the National Animal Nutrition Program (NANP [6]) was initiated in 2010 and is supported as a National Research Support Project with hatch funds administered by the USDA before the formula distribution to state experiment stations. The NANP is focused on addressing challenges facing researchers in animal agriculture and filling voids in the animal nutrition research and academic communities. An integrated and systematic approach is used to share, collect, assemble, synthesize, and disseminate science-based information, educational tools, and enabling technologies regarding agricultural animal nutrition, with an emphasis on beef, dairy, swine, and poultry. The purpose of NANP is to identify the current state of coordination and networking within animal nutrition; explore animal nutrition over time, across geographic locations, by topic, and by networks of collaborators in animal nutrition research; define high-priority animal nutrition issues; and foster new and existing collaborations to facilitate solutions to these issues. The committee interacts with the NRC on critical national priorities in animal nutrition and provides a forum to address research support needs. The NANP consists of a coordinating committee which oversees 2 additional committees: (1) a modeling committee that focuses on improving the use of predictive technologies and tools, enables the use of common software platforms, and works with researchers to develop and share models and modeling information; and (2) a feed composition
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The NRC is a nongovernmental institution, yet it does receive a small amount of federal money to support its functions. Because of this, it is subject to particular federal policies, including the Freedom of Information Act [4] and the Federal Advisory Committee Act [5]. When it comes to convening ad hoc committees to write the reports, federal policies do not play a large role in the functionality of the committee’s work other than directing the flow of information from the public to the committee and verifying that the committee members do not have a conflict of interest in the report itself. In establishing the financial support for each publication, the NRC is reliant on numerous external funding sources. The NRC reinvests some of the income from sales of prior reports into development and production costs. Today, this investment only covers 25 to 30% of the costs of any species nutrient requirement publication. To give a sense of cost, it is estimated that the cost of the next publication (dairy) will be $400,000 in 2014 or 2015. Therefore, financial contributions for these publications must come from other sectors. The FDA Center for Veterinary Medicine has been a consistent donor toward these efforts in recent years. Additionally, the majority of the funds must come from entities that do not bear any direct financial benefit from any specific aspect of the publication. Thus, the large proportion of funding for a revision must come from not-for-profit or public entities (e.g., commodity check-off, donations to or from an animal or feed industry foundation, and so on). However, 49% of the funding for such an effort can come from directly from the poultry and allied industries. For many years, consistency of the publications and cohesiveness across publications was overseen by the Committee on Animal Nutrition
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Table 2. Published literature used for the basis of NRC [3] recommendations for dietary amino acid concentrations and phosphorus (range of years for the basis of NRC [3] recommendations) Nutrient Amino acid Phosphorus
Broilers
Turkeys
Laying hens
1947–1991 1952–1983
1949–1986 1954–1986
1962–1989 1983–1987
WHAT NEW SCIENTIFIC INFORMATION HAS BEEN DISCOVERED SINCE 1994? The NRC [3] amino acid and phosphorus recommendations for poultry were based on the latest peer-reviewed literature to that time, but, as exemplified within Table 2, the literature used is now (in 2014) 23 yr old for amino acid recommendations and 31 yr old for phosphorus for broilers. However, the present commercial bird is very different from commercial birds available before 1991, due in part to genetic selection as well as management practice- and feedrelated changes [7–9]. For example, the national average BW for turkey toms at 18 wk of age was only 10.9 kg in 1986 [10] versus over 18.2 kg today. A quick search of literature (Agricola, key words: nutrient, requirement, and broiler) notes that substantial peer-reviewed literature exists on several key nutrient areas, namely that of amino acids and mineral nutrition (Table 3). Additional changes have shaped the poultry industry since the 1994 publication [3], including bird genotype; feed ingredient composition, as genotypic and phenotypic selection has occurred (e.g., corn with lower protein and proportional increases in starch content); increased use of co-products (e.g., distillers dried grains with varying amounts of solubles); enzyme supplementation; as well as realization and quantification of different nutrient and energy digest-
ibility coefficients in growing birds. Whereas our collective poultry scientific community has addressed several of these particular issues, we have chosen to highlight progress on amino acid and phosphorus responses in the scientific literature in the following subsections. Amino Acid Requirements A few recent publications have challenged the NRC recommendations for amino acids as being inadequate for current poultry strains. Dozier et al. [11] summarized the amino acid requirements of broilers in weekly durations based on studies conducted since publication of the NRC guidelines [3] until 2007 and suggested much greater amino acid needs for optimal growth and muscle deposition. In turkeys, however, feeding of 110% of the NRC recommendations [3] did not improve turkey tom performance or yields [12]. A different turkey study, by Noll et al. (as cited by Lunden [13]), suggested that when a CP minimum is included in the formulation, BW was not significantly affected by 100 versus 110% of NRC CP requirements (18.7 vs. 19.3 kg, respectively [3]). However, FCR was 0.03 lower, and breast yield (percent of carcass) was 1.5 percentage units greater in birds fed 110% of NRC requirements [3]. Table 3. Published literature since referenced citations in NRC [3] Nutrient Lys TSAA Val Arg Ile Ca P 1
Publication date1
Number of published papers2
1981 to 2013 1985 to 2013 1990 to 2013 1990 to 2013 1990 to 2013 1982 to 2013 1983 to 2013
>40 20 7 12 8 9 14
Starting date was after the date of the last cited reference for NRC [3]. 2 Agricola search (key words: nutrient, requirement, and broilers).
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committee that assembles data and researches resources on feed composition, fosters communication among those collecting feed composition information, and improves efficiency and consistency in data collection and maintenance. Examples of current accomplishments include development of a modeling template to use across NRC publication updates; corrections and software updates to dairy models; and development of feed ingredient database structure for online public access [6].
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Phosphorus Requirements As detailed by Applegate and Angel [15], substantial research has been conducted in broilers and laying hens to further define phosphorus needs since the 1980s-based publications that were the foundation for the recommendations in the NRC [3] publication. However, overfeeding of dietary P is common commercially, with excesses of 20 to 100% over published requirements commonly observed. In the United States, part of this overfeeding is due to a lack of a centralized, up-to-date source of information on poultry P requirements (e.g., a current NRC publication), lack of information on digestible P in ingredients, and no information on ingredient concentrations with variability and number of analysis represented associated with it. Additionally, when the NRC requirements [3] were put forth, phytase was just entering the commercial market. Further, phosphorus nomenclature between the eighth [2] and ninth [3] NRC publications induced confusion by many, in that the 1984 publication [2] used an available P (aP) nomenclature, yet the 1994 publication [3] used a nonphytate P (nPP) nomenclature without substantial change in the values resulting in feed ingredients having similar aP and nPP concentrations between these revisions. These terminologies are not synonymous, as aP refers to the P that is absorbed from the diet into the animal (i.e., feed P minus P within the distal ileum; a biologically available term) versus nPP, which is chemically determined (total P minus phytate
P). Unfortunately, the aP used by the NRC [2] publication is based in large part on calculations developed in the 1950s that took P from a total to an aP nomenclature. Part of the shift in thinking between 1984 and 1994 was to clarify terminologies and gain clarity in the literature with regard to experimental design. Since that time, substantial discussion has taken place among the poultry and swine scientific communities on development of consensus protocols for ingredient aP. In particular, Nutrition Working Group of the European branch of the World’s Poultry Science Association published [16] consensus protocols for aP determinations, including procedures for the determination of nutrient hydrolysis per unit of enzyme inclusion. For a historical perspective on biological determination of phosphorus availability, please refer to the review by Shastak and Rodehutscord [17].
HOW CHANGES TO COMPOSITIONAL GROWTH AFFECT NUTRIENT NEEDS It is well accepted that of the major poultry species, some of the most pronounced gains in selection for growth and improved yields have been in the broiler. The question debated by many when it comes to discussion of a revision to the NRC requirements [3] is whether increases in feed (and thus nutrient) intake are commensurate with growth needs. However, often missing from this discussion are changes to composition of growth (or egg production) per unit of feed intake. Havenstein et al. [7, 8] noted substantial growth improvement in comparing a random bred bird from 1957 versus an Arbor Acres bird from 1991 and a Ross 308 from 2001. These dramatic improvements in gain are exemplified in Table 4. When these strains were fed diets representative of 1957 and 2001, it became clear that broilers cannot fully compensate for a poor quality feed by simply eating more [8]. Similar improvements in growth were noted in summarizing commercial production in Brazil from 1990 to 2009 by Patricio et al. [18], in that adjusted FCR to 2.0 kg was 1.96 and 1.57, respectively. These changes in growth largely speak to a differential need for ME per unit of feed intake (i.e., caloric efficiency) possibly related to different maintenance requirements with
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In the case of laying hens, CP and amino acid formulations are largely over-formulated versus NRC requirements [3], with the hope of getting a return in either egg size or egg number. Research by Applegate et al. [14], however, suggests that 15.3 g of CP/hen per day (858 mg of Lys, 450 mg of Met, 585 mg of Thr, and 638 mg of Ile per hen per day) is sufficient to maximize egg weight and production from 25 to 45 wk of age versus birds fed corn-soybean meal diets containing 16.15 g of CP/hen per day (874 mg of Lys, 409 mg of Met, 627 mg of Thr, and 684 mg of Ile per hen per day). Notably, 15.3 g of CP/hen per day supplied 2% greater CP (24, 50, and 24% more Lys, Met, and Thr, respectively) versus the NRC recommendations [3].
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BW (g/d to 42 d of age)
FCR to 42 d of age
FCR to 700 g
11.8 49.8 62.6
2.45 2.00 1.58
2.59 (56 d) 1.58 (21 d) 1.31 (21 d)
1957 Athens-Canadian Random-bred 1991 Arbor Acres 2001 Ross 308
and a fast-growing broiler strain (Table 7). They concluded that the fast-growing strain was less mineralized and had more porous cortical bone than that of the slow-growing strain. Whereas the reduced calcium and phosphorus content in the tibia may counteract differences in the relative requirements per unit of intake; it emphasizes the need for improved precision in mineral nutrition in the modern broiler.
WHAT IS A NUTRIENT REQUIREMENT? Though this may seem like a simple question, it is not easily answered and our definitions have substantially changed since the first NRC poultry publication in 1944 [1]. Leeson and Summers [21] defined a nutrient requirement as “the minimum amount of the nutrient required to produce the best weight gain, feed efficiency, etc. and the lack of any signs of nutritional deficiency,” which are often referred to as the “minimum nutrient needs.” Admittedly, they offer substantial examples wherein various factors would influence these needs, and thus have led to the imposition of “margins of safety” to which the NRC requirements [1] used the term “allowances” rather than requirements, as additional allowances are “needed to provide for the contingencies which are inherent in the manufacture, transportation and use of poultry
Table 5. Broiler body, tissue and organ growth differences between a heritage line (University of Illinois, UrbanaChampaign) from 1940 versus Ross 708 broiler from 2007 (adapted from Schmidt et al. [19]) Breast Strain 1940 heritage 2007 Ross 708 2007 vs. 1940 1
Small intestine
BW gain (g/d)
g/d
AG1
mg/d
mg/g of BW
cm/d
cm/bird2
30.8 53.1 1.8
1.6 6.1 3.8
1.09 1.25
240 316 1.3
7 5 0.7
1.8 2.5 1.4
123 141 1.1
Allometric growth (AG) coefficient after 14 d of age. Length to a similar BW.
2
Heart
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improvements in growth that have occurred over time. Additionally, if one looks at composition of growth over time, the proportional growth of muscle and intestine far surpass that of other organs, such as the heart and skeleton. For example, Schmidt et al. [19] compared tissue growth differences between a heritage line (random bred since 1940) from the University of Illinois, Urbana-Champaign, and Ross 708 (late 2000s). Notably, the growth of the breast muscle was 3.8-fold greater, the small intestine was 1.14-fold longer, and growth of the heart was only 0.7 in the Ross 708 versus that in the heritage line (Table 5). This begs the question as to how nutrient needs, amino acids in particular, have shifted as composition of the carcass has changed. To that end, if one uses predictions for growth versus nutrient needs, comparisons can be made utilizing the NRC guidelines [3] and publications such as the Brazilian broiler nutrient requirement tables [20]. Notably, the Brazilian model predicts a 20% greater digestible Lys need by the broiler to 17 d or a common 2.1 kg of BW as compared with the NRC guidelines [3]. Much of this additional Lys need is directly attributable to compositional differences per unit of BW rather than only differences in intake or rate of BW growth to a common BW (Table 6). Similarly, Williams et al. [9] reported differences in tibia characteristics between a slow-
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Table 6. Predicted growth and digestible Lys requirement per NRC [3] versus Rostagno et al. [20] at 17 d of age and a common 2 kg of BW Reference NRC Rostagno et al. NRC Rostagno et al.
Age (d)
BW (kg)
FCR
Digestible Lys (%)
17 17 42 32
0.68 0.70 2.09 2.07
1.43 1.38 1.82 1.55
0.98 1.23 0.87 1.10
to or below their requirement (e.g., phosphorus), the variability in response of the population increases. Similarly, birds within the flock respond differently to a challenge, thus increasing this variation. This is of particular economic consideration, as substantial yearly improvements in performance (meat yield, egg production) continue beyond what we traditionally think of as the breakpoint. To further complicate issues, the literature is pervasive with different presentation and terminology related to requirements, including that of a breakpoint determined through broken-line analyses (optimum nutrient return per unit of nutrient input for a measured characteristic), a quadratic asymptote (maximum or minimum), or a percentage (e.g., 90 or 95%) of the asymptote. Either way, these measures average the response of the population, whereas, more times than not, the variance around that mean gets lost in interpretation. Regardless, the NRC committees are tasked with utilizing the best information available. This leads us to ask, “Why and in what circumstances would the variance matter?” Case in point would be related to that of skeletal and leg abnormalities and industry formulation targets for macrominerals and vitamin D3. Historically, the industry has supplemented vitamin D3 at concentrations well above what is typically reported as the requirement. For example, Edwards et al. [25] reported the vitamin D3 requirement of broilers for growth to be 275 IU/kg, for bone ash
Table 7. Broiler tibia growth and mineral characteristics between a slow and fast broiler strain (as adapted from Williams et al. [9]) Broiler strain Slow Fast
Tibia width (mm/kg of BW at 42 d)
Tibia length (mm/kg of BW at 42 d)
Tibia ash
Tibia
(%, 4 d)
(%, 42 d)
(% Ca)
(% P)
5.3 2.6
94.1 39.3
41 29
58 46
26.9 18.5
11.4 8.4
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feeds.” In today’s ingredient pricing environment, we likely can no longer afford this vague notion for unspecified margins of safety without a quantifiable performance or yield response to nutrient input variation. Thus, Ahmad and Roland [22] and Gous [23] have suggested that we rather should be discussing nutrient “responses” rather than requirements per se; encompassing considerations of marginal cost of ingredient or nutrient input versus marginal returns of product. This concept becomes rather complicated in our traditional view of nutrient requirement tables, as prior nutrient intake influences current and future performance responses. Furthermore, as the broiler market now has a different ending BW, optimization of these birds’ different ending BW and composition will take different nutrient response curves. Thus, modeling of nutrient responses based on the desired end product offers a more dynamic applicability than static requirements in tabular form. Part of this complexity is also due to (1) individual responses within a particular environment, (2) variation in nutrient delivery to the bird versus what was formulated, (3) variation in ingredient nutrient composition, and (4) feed management systems that include free choice or restricted intakes. The response from insufficiency to sufficiency becomes curvilinear, because we determine the response for a population, and not the individual. Work by Schinckel et al. [24] suggests that as birds are fed closer
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CONCLUSIONS AND APPLICATIONS
1. Much has changed with animal nutrition since the inception of NRC nutrient requirement publications. 2. Nevertheless, their tradition of scientific rigor and independence has allowed them to become benchmarks for the scientific, judicial, and regulatory communities domestically and abroad. 3. Substantial time has passed and scientific progress has been made since the ninth revised edition of the NRC Nutrient Requirements for Poultry in 1994. Of the 4 primary livestock species, the poultry
publication is the oldest revised edition, with beef being currently updated and dairy undergoing committee formation and financial organization (last revision in 2001), and swine having been recently updated in 2012. 4. Several challenges need to be faced if an update is to be made to the poultry NRC requirements beyond the need for substantial commitments of financial resources from all sources and volunteer time from scientists. 5. The first challenge is to find a consensus among industry and scientists that a new NRC guideline for poultry is needed.
REFERENCES AND NOTES 1. NRC. 1944. Recommended Nutrient Allowances for Poultry. 1st ed. Natl. Acad. Press, Washington, DC. 2. NRC. 1984. Nutrient Requirements of Poultry. 8th rev. ed. Natl. Acad. Press, Washington, DC. 3. NRC. 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC. 4. United States Government. 2011. 5 USC § 552: Public information; agency rules, opinions, orders, records, and proceedings. Accessed Jun. 11, 2014. http://www.gpo.gov/ fdsys/pkg/USCODE-2010-title5/pdf/USCODE-2010-title5partI-chap5-subchapII-sec552.pdf. 5. United States Government. 2009. 5 USC App. II § 1–15: Federal advisory committee act. Accessed Jun. 11, 2014. http://www.gpo.gov/fdsys/pkg/USCODE-2010-title5/ html/USCODE-2010-title5-app-federalad.htm. 6. USDA-National Institute of Food and Agriculture. 2014. Ongoing details regarding the activities and accomplishments of the National Animal Nutrition Program. Accessed June 4, 2014. http://nanp-nrsp-9.org. 7. Havenstein, G. B., P. R. Ferket, S. E. Scheidler, and B. T. Larson. 1994. Growth, livability, and feed conversion of 1991 vs 1957 broilers when fed “typical” 1957 and 1991 broiler diets. Poult. Sci. 73:1785–1794. 8. Havenstein, G. B., P. R. Ferket, and M. A. Qureshi. 2003. Carcass composition and yield of 1957 versus 2001 broilers when fed representative 1957 and 2001 broiler diets. Poult. Sci. 82:1509–1518. 9. Williams, B., S. Solomon, D. Waddington, B. Thorp, and C. Farquharson. 2000. Skeletal development in the meat-type chicken. Br. Poult. Sci. 41:141–149. 10. Ferket, P.R. 2003. Growth of toms improves substantially. Pages 38–48 in WATT Poultry USA, July 2003. Rockford, IL. 11. Dozier, W. A., III, M. T. Kidd, and A. Corzo. 2008. Amino acid responses of broilers. J. Appl. Poult. Res. 17:157–167. 12. Applegate, T., W. J. Powers, R. Angel, and D. Hoehler. 2008. Effect of amino acid formulation and acid supplementation on performance and nitrogen excretion in turkey toms. Poult. Sci. 87:514–520. 13. Lunden, T. 2009. Protein improves turkey gain. Feedstuffs 81:10–12.
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to be 503 IU/kg, for plasma Ca to be 552 IU/kg, and for rickets prevention to be 904 IU/kg; yet broiler and turkey diets routinely contain 2,000 to over 5,000 IU/kg. This over-supplementation is a partial reflection of a report by Yang et al. [26]. In that report, they evaluated 26 vitamin D3 supplements using a biological response in turkey poults of changes in femur ash content; the supplements elicited a range of bio-potencies of 40 to 134%. Thus, they recommended an oversupplementation of vitamin D3 by 3 to 4 times the requirement as an insurance factor. More recent evaluations of sources of vitamin D3 across the industry resulted in a reduced variation in a broiler bio-assay (86 to 118% [27]). This, coupled with much improved methods of chemical analyses, has greatly improved our confidence in the concentration and bio-potency of the vitamin received by our birds, but has not changed industry supplementation concentrations for vitamin D3 41 yr after that initial report on variable bio-potency of commercial D3 sources. Only under regulatory constraints have industry use concentrations changed (e.g., Europe). Industry has hesitated to reduce D3 concentrations as leg problems continue to be a concern. In recent years, the US broiler industry has increased the proportion of birds produced toward the heavy roasters market, and the weight of broilers has increased to maximize processing plant margins. With these increases in BW at processing, the reported incidence of late mortalities, most associated with gait and or leg abnormalities, has increased by 1 to 1.5%, resulting in substantial economic losses.
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22. Ahmad, H. A., and D. A. Roland Sr. 2003. Effect of method of feeding and feed formulation on performance and profitability of laying hens: An econometric approach. J. Appl. Poult. Res. 12:291–298. 23. Gous, R. M. 2014. Modeling as a research tool in poultry science. Poult. Sci. 93:1–7. 24. Schinckel, A. P., O. Adeola, and M. E. Einstein. 2005. Evaluation of alternative nonlinear mixed effects model of duck growth. Poult. Sci. 84:256–264. 25. Edwards, H. M., Jr., M. A. Elliot, S. Sooncharerynying, and W. M. Britton. 1994. Quantitative requirement for cholecalciferol in the absence of ultraviolet light. Poult. Sci. 73:288–294. 26. Yang, H. S., P. E. Waibel, and J. Brenes. 1973. Evaluation of vitamin D3 supplements by biological assay using the turkey. J. Nutr. 103:1187–1194. 27. Kasim, A. B., and H. M. Edwards Jr. 2000. Evaluation of cholecalciferol sources using broiler chick assays. Poult. Sci. 79:1617–1622.
Acknowledgments
This paper is a summation of concepts from a 2013 Poultry Science Association (PSA) symposium, entitled “Nutrient Requirement Evaluation and Publication for Poultry: US and Global Perspectives.” Presentations from that symposium are archived and accessible through the following PSA website: http://www.poultryscience.org/psa13/recordingsNREaPfPUaG.asp. This paper was previously presented at the 2014 Mid-Atlantic Nutrition Conference in Timonium, Maryland.
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14. Applegate, T. J., E. Onyango, R. Angel, and W. J. Powers. 2009. Effect of amino acid formulation and dietary probiotic supplementation on egg production and egg characteristics in laying hens. J. Appl. Poult. Res. 18:552–561. 15. Applegate, T. J., and R. Angel. 2008. Phosphorus requirements for poultry. AS-583-W Purdue Univ. Coop. Ext., West Lafayette, IN. Accessed June 4, 2014. http://www. extension.purdue.edu/extmedia/AS/AS-583-W.pdf. 16. Working Group No 2: Nutrition of the European Federation Branch of WPSA. 2013. Determination of phosphorus availability in poultry. World’s Poult. Sci. J. 69:687– 698. 17. Shastak, Y., and M. Rodehutscord. 2013. Determination and estimation of phosphorus availability in growing poultry and their historical development. World’s Poult. Sci. J. 69:569–586. 18. Patricio, I. S., A. A. Mendes, A. A. Ramos, and D. F. Pereira. 2012. Overview on the performance of Brazilian broilers (1990 to 2009). Brazil. Jpn. Poult. Sci. 14:233–304. 19. Schmidt, C. J., M. E. Persia, E. Feierstein, B. Kingham, and W. W. Saylor. 2009. Comparison of a modern broiler line and a heritage line unselected since the 1950s. Poult. Sci. 88:2610–2619. 20. Rostagno, H. S., L. F. T. Albino, J. L. Donzele, P. C. Gomes, R. F. de Oliveira, D. C. Lopes, A. S. Ferreira, S. L. T. Barreto, and R. F. Euclides. 2011. Brazilian Tables for Poultry and Swine: Composition of Feedstuffs and Nutritional Requirements. 3rd ed. H.S. Rostagno, ed. Federal Univ. Viҫosa, Viҫosa, Brazil. 21. Leeson, S., and J. D. Summers. 2001. Nutrition of the Chicken. 4th ed. University Books, Guelph, Ontario, Canada.
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Nutrient requirements of poultry publication: History and need for an update Todd J. Applegate*1 and Roselina Angel† *Department of Animal Sciences, Purdue University, West Lafayette, IN 47907; and †Department of Animal and Avian Sciences, University of Maryland, College Park 20742-0001
SUMMARY The NRC Nutrient Requirements of Poultry has been a benchmark publication for the research, judicial, and regulatory communities domestically and abroad since the first published edition in 1944. The poultry scientific community has looked to this publication for benchmark diet formulation. With extraordinary changes in growth and productive potential of modern poultry strains, as well as changes to body composition and egg output, it follows that nutrient needs have changed beyond what the bird can compensate for with increasing intake per unit of BW. Research publications used for amino acid and phosphorus recommendations in the last NRC are now, at best, from 1991 and at worst from 1947. To our collective credit, the poultry science community has published substantial amounts of data in those areas to warrant an update to the ninth revised edition of the NRC Nutrient Requirements of Poultry. Historically, our perception and definition of a nutrient requirement has changed from first being a requirement, as a percent of a diet, to preventing a nutrient deficiency, to now being a requirement to optimize growth or egg production response per unit of nutrient intake. As economics becomes an increasingly more important driver for the implications of research, the scientific community has begun to embrace the concept of return on investment of nutrient used for compositional growth or egg production. As these concepts take shape, the current edition’s format will have to undergo a substantial creative revision; possibly even embracing the concept of modeling of nutrient responses. Funding for such a revision will require a large financial investment from the NRC, the feed industry, commodity associations, as well as time investment by the scientific community. Key words: poultry, nutrient requirement, National Research Council 2014 J. Appl. Poult. Res. 23:567–575 http://dx.doi.org/10.3382/japr.2014-00980
HISTORY OF THE NRC AND NUTRIENT REQUIREMENT PUBLICATIONS The NRC is the operational arm of the National Academy of Sciences (NAS; established 1
Corresponding author: [email protected]
in 1863), which combined with the National Academy of Engineering and Institute of Medicine in 2013. There are 6 divisions of the NAS, one of which is the Division of Earth and Life Sciences, which is home to 12 boards. The primary board the poultry community would be
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Primary Audience: Poultry Nutritionists, Feed Industry, Government Agencies, Regulatory Committee
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Table 1. History of revisions to NRC Nutrient Requirements of Poultry, Beef, Dairy, and Swine publications (by year) Poultry
1945 1950 1963 1976 1984 1996 2000 2014 (estimated)
familiar with is the Board on Agriculture and Natural Resources. Among this board’s function is to appoint ad hoc committees to develop NRC reports. Notably, the NRC releases approximately one report each working day on issues in science, technology, medicine, social science, and education. The NAS established the NRC in 1916 after a request by President Woodrow Wilson to recruit specialists from the larger scientific and technological communities to participate in and support the work of the NAS. During World War II, the Committee on Animal Nutrition through the NRC was tasked with improving animal nutrition to ensure an adequate food supply for the population during emergency war times. The inception of the Nutrient Requirements of Poultry report from the NRC began with the first 18page edition being published in 1944 [1]. Interestingly, the concept of a requirement was not in place at that time; rather values were listed as nutrient allowances without inclusion of margins of safety. As noted in Table 1, the publication was consistently revised at least every 6 or 7 yr until the 1984, eighth revised edition [2], with the ninth coming 10 yr later [3]. The frequency of updates early in the history of the publication was notable, as new nutrients were being discovered and the relevance of those nutrients for poultry nutrition were established. Inasmuch, the NRC has considered 4 species of upmost importance to consistently update the nutrient requirement publications, namely beef, dairy, poultry, and swine. As updates to the NRC publications were fairly routine over its last 50-yr history, the regulatory and judicial communities
Dairy 1945 1950 1956 1958 1966 1971 1978 1988 2001 2015 or 2016 (estimated)
Swine 1944 1950 1953 1959 1964 1968 1979 1988 1998 2012
in the United States and abroad have used these publications as benchmarks for their guidance. The NRC publications have therefore become very valuable references for regulatory agencies (domestically and internationally), as they are comprehensive evaluations of credible and generally accepted science (for the most part based on published peer-reviewed information) that was current at the time of publication. For example, the US Food and Drug Administration (FDA) makes its scientific determinations to support regulatory processes based on standards that are scientifically sound and consistent; otherwise, the determinations could be viewed as arbitrary and capricious. Traditionally, the FDA uses NRC publications as a standard when making determinations with regard to nutrient recommendations in the evaluation of utility or functionality of substances added to animal feed, as well as during assessment of the safety and toxicity of those substances. The information available in NRC publications regarding toxicity of nutrients or other additives, including tissue levels, maximum tolerable levels, and so on, is regularly used to determine the safety of substances used in animal feed during pre- or postmarket valuations of product safety or the truthfulness of labeling. The US FDA continues to use information in NRC publications as the gold standard when making regulatory determinations. Recognizing the value and merit of NRC publications, the FDA Center for Veterinary Medicine still partially funds relevant NRC publications. However, the FDA also recognizes that some of the information in old NRC publications can be
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1944 1946 1950 1954 1960 1966 1971 1977 1984 1994
Beef
Applegate and Angel: REVISION FOR NUTRIENT REQUIREMENTS somewhat dated; and thus the FDA makes reasonable adjustments and minor deviations from information gathered in NRC publications based on current science and facts when making its determinations.
WHAT HAS CHANGED IN THE UNITED STATES SINCE PUBLICATION OF THE NINTH REVISED VERSION IN 1994?
through the NRC. As mentioned earlier, the primary focus of the initial Committee on Animal Nutrition work was to ensure an adequate food supply, which was accomplished in part through publishing the nutrient requirement publications for livestock and poultry. Currently, this responsibility rests with the Animal Nutrition Program of the Board on Agriculture and Natural Resources (BANR). Today, the major focus of BANR work is centered in 4 areas: (1) environmental quality, refining animal feeding to reduce environmental effects; (2) animal production, improving animal productivity and efficiency; (3) food safety, enhancing the quality and safety of food products derived from animal sources; and (4) animal and human health, ensuring the health and well-being of animals and humans. To help support the Animal Nutrition Program of BANR, the National Animal Nutrition Program (NANP [6]) was initiated in 2010 and is supported as a National Research Support Project with hatch funds administered by the USDA before the formula distribution to state experiment stations. The NANP is focused on addressing challenges facing researchers in animal agriculture and filling voids in the animal nutrition research and academic communities. An integrated and systematic approach is used to share, collect, assemble, synthesize, and disseminate science-based information, educational tools, and enabling technologies regarding agricultural animal nutrition, with an emphasis on beef, dairy, swine, and poultry. The purpose of NANP is to identify the current state of coordination and networking within animal nutrition; explore animal nutrition over time, across geographic locations, by topic, and by networks of collaborators in animal nutrition research; define high-priority animal nutrition issues; and foster new and existing collaborations to facilitate solutions to these issues. The committee interacts with the NRC on critical national priorities in animal nutrition and provides a forum to address research support needs. The NANP consists of a coordinating committee which oversees 2 additional committees: (1) a modeling committee that focuses on improving the use of predictive technologies and tools, enables the use of common software platforms, and works with researchers to develop and share models and modeling information; and (2) a feed composition
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The NRC is a nongovernmental institution, yet it does receive a small amount of federal money to support its functions. Because of this, it is subject to particular federal policies, including the Freedom of Information Act [4] and the Federal Advisory Committee Act [5]. When it comes to convening ad hoc committees to write the reports, federal policies do not play a large role in the functionality of the committee’s work other than directing the flow of information from the public to the committee and verifying that the committee members do not have a conflict of interest in the report itself. In establishing the financial support for each publication, the NRC is reliant on numerous external funding sources. The NRC reinvests some of the income from sales of prior reports into development and production costs. Today, this investment only covers 25 to 30% of the costs of any species nutrient requirement publication. To give a sense of cost, it is estimated that the cost of the next publication (dairy) will be $400,000 in 2014 or 2015. Therefore, financial contributions for these publications must come from other sectors. The FDA Center for Veterinary Medicine has been a consistent donor toward these efforts in recent years. Additionally, the majority of the funds must come from entities that do not bear any direct financial benefit from any specific aspect of the publication. Thus, the large proportion of funding for a revision must come from not-for-profit or public entities (e.g., commodity check-off, donations to or from an animal or feed industry foundation, and so on). However, 49% of the funding for such an effort can come from directly from the poultry and allied industries. For many years, consistency of the publications and cohesiveness across publications was overseen by the Committee on Animal Nutrition
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Table 2. Published literature used for the basis of NRC [3] recommendations for dietary amino acid concentrations and phosphorus (range of years for the basis of NRC [3] recommendations) Nutrient Amino acid Phosphorus
Broilers
Turkeys
Laying hens
1947–1991 1952–1983
1949–1986 1954–1986
1962–1989 1983–1987
WHAT NEW SCIENTIFIC INFORMATION HAS BEEN DISCOVERED SINCE 1994? The NRC [3] amino acid and phosphorus recommendations for poultry were based on the latest peer-reviewed literature to that time, but, as exemplified within Table 2, the literature used is now (in 2014) 23 yr old for amino acid recommendations and 31 yr old for phosphorus for broilers. However, the present commercial bird is very different from commercial birds available before 1991, due in part to genetic selection as well as management practice- and feedrelated changes [7–9]. For example, the national average BW for turkey toms at 18 wk of age was only 10.9 kg in 1986 [10] versus over 18.2 kg today. A quick search of literature (Agricola, key words: nutrient, requirement, and broiler) notes that substantial peer-reviewed literature exists on several key nutrient areas, namely that of amino acids and mineral nutrition (Table 3). Additional changes have shaped the poultry industry since the 1994 publication [3], including bird genotype; feed ingredient composition, as genotypic and phenotypic selection has occurred (e.g., corn with lower protein and proportional increases in starch content); increased use of co-products (e.g., distillers dried grains with varying amounts of solubles); enzyme supplementation; as well as realization and quantification of different nutrient and energy digest-
ibility coefficients in growing birds. Whereas our collective poultry scientific community has addressed several of these particular issues, we have chosen to highlight progress on amino acid and phosphorus responses in the scientific literature in the following subsections. Amino Acid Requirements A few recent publications have challenged the NRC recommendations for amino acids as being inadequate for current poultry strains. Dozier et al. [11] summarized the amino acid requirements of broilers in weekly durations based on studies conducted since publication of the NRC guidelines [3] until 2007 and suggested much greater amino acid needs for optimal growth and muscle deposition. In turkeys, however, feeding of 110% of the NRC recommendations [3] did not improve turkey tom performance or yields [12]. A different turkey study, by Noll et al. (as cited by Lunden [13]), suggested that when a CP minimum is included in the formulation, BW was not significantly affected by 100 versus 110% of NRC CP requirements (18.7 vs. 19.3 kg, respectively [3]). However, FCR was 0.03 lower, and breast yield (percent of carcass) was 1.5 percentage units greater in birds fed 110% of NRC requirements [3]. Table 3. Published literature since referenced citations in NRC [3] Nutrient Lys TSAA Val Arg Ile Ca P 1
Publication date1
Number of published papers2
1981 to 2013 1985 to 2013 1990 to 2013 1990 to 2013 1990 to 2013 1982 to 2013 1983 to 2013
>40 20 7 12 8 9 14
Starting date was after the date of the last cited reference for NRC [3]. 2 Agricola search (key words: nutrient, requirement, and broilers).
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committee that assembles data and researches resources on feed composition, fosters communication among those collecting feed composition information, and improves efficiency and consistency in data collection and maintenance. Examples of current accomplishments include development of a modeling template to use across NRC publication updates; corrections and software updates to dairy models; and development of feed ingredient database structure for online public access [6].
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Phosphorus Requirements As detailed by Applegate and Angel [15], substantial research has been conducted in broilers and laying hens to further define phosphorus needs since the 1980s-based publications that were the foundation for the recommendations in the NRC [3] publication. However, overfeeding of dietary P is common commercially, with excesses of 20 to 100% over published requirements commonly observed. In the United States, part of this overfeeding is due to a lack of a centralized, up-to-date source of information on poultry P requirements (e.g., a current NRC publication), lack of information on digestible P in ingredients, and no information on ingredient concentrations with variability and number of analysis represented associated with it. Additionally, when the NRC requirements [3] were put forth, phytase was just entering the commercial market. Further, phosphorus nomenclature between the eighth [2] and ninth [3] NRC publications induced confusion by many, in that the 1984 publication [2] used an available P (aP) nomenclature, yet the 1994 publication [3] used a nonphytate P (nPP) nomenclature without substantial change in the values resulting in feed ingredients having similar aP and nPP concentrations between these revisions. These terminologies are not synonymous, as aP refers to the P that is absorbed from the diet into the animal (i.e., feed P minus P within the distal ileum; a biologically available term) versus nPP, which is chemically determined (total P minus phytate
P). Unfortunately, the aP used by the NRC [2] publication is based in large part on calculations developed in the 1950s that took P from a total to an aP nomenclature. Part of the shift in thinking between 1984 and 1994 was to clarify terminologies and gain clarity in the literature with regard to experimental design. Since that time, substantial discussion has taken place among the poultry and swine scientific communities on development of consensus protocols for ingredient aP. In particular, Nutrition Working Group of the European branch of the World’s Poultry Science Association published [16] consensus protocols for aP determinations, including procedures for the determination of nutrient hydrolysis per unit of enzyme inclusion. For a historical perspective on biological determination of phosphorus availability, please refer to the review by Shastak and Rodehutscord [17].
HOW CHANGES TO COMPOSITIONAL GROWTH AFFECT NUTRIENT NEEDS It is well accepted that of the major poultry species, some of the most pronounced gains in selection for growth and improved yields have been in the broiler. The question debated by many when it comes to discussion of a revision to the NRC requirements [3] is whether increases in feed (and thus nutrient) intake are commensurate with growth needs. However, often missing from this discussion are changes to composition of growth (or egg production) per unit of feed intake. Havenstein et al. [7, 8] noted substantial growth improvement in comparing a random bred bird from 1957 versus an Arbor Acres bird from 1991 and a Ross 308 from 2001. These dramatic improvements in gain are exemplified in Table 4. When these strains were fed diets representative of 1957 and 2001, it became clear that broilers cannot fully compensate for a poor quality feed by simply eating more [8]. Similar improvements in growth were noted in summarizing commercial production in Brazil from 1990 to 2009 by Patricio et al. [18], in that adjusted FCR to 2.0 kg was 1.96 and 1.57, respectively. These changes in growth largely speak to a differential need for ME per unit of feed intake (i.e., caloric efficiency) possibly related to different maintenance requirements with
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In the case of laying hens, CP and amino acid formulations are largely over-formulated versus NRC requirements [3], with the hope of getting a return in either egg size or egg number. Research by Applegate et al. [14], however, suggests that 15.3 g of CP/hen per day (858 mg of Lys, 450 mg of Met, 585 mg of Thr, and 638 mg of Ile per hen per day) is sufficient to maximize egg weight and production from 25 to 45 wk of age versus birds fed corn-soybean meal diets containing 16.15 g of CP/hen per day (874 mg of Lys, 409 mg of Met, 627 mg of Thr, and 684 mg of Ile per hen per day). Notably, 15.3 g of CP/hen per day supplied 2% greater CP (24, 50, and 24% more Lys, Met, and Thr, respectively) versus the NRC recommendations [3].
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BW (g/d to 42 d of age)
FCR to 42 d of age
FCR to 700 g
11.8 49.8 62.6
2.45 2.00 1.58
2.59 (56 d) 1.58 (21 d) 1.31 (21 d)
1957 Athens-Canadian Random-bred 1991 Arbor Acres 2001 Ross 308
and a fast-growing broiler strain (Table 7). They concluded that the fast-growing strain was less mineralized and had more porous cortical bone than that of the slow-growing strain. Whereas the reduced calcium and phosphorus content in the tibia may counteract differences in the relative requirements per unit of intake; it emphasizes the need for improved precision in mineral nutrition in the modern broiler.
WHAT IS A NUTRIENT REQUIREMENT? Though this may seem like a simple question, it is not easily answered and our definitions have substantially changed since the first NRC poultry publication in 1944 [1]. Leeson and Summers [21] defined a nutrient requirement as “the minimum amount of the nutrient required to produce the best weight gain, feed efficiency, etc. and the lack of any signs of nutritional deficiency,” which are often referred to as the “minimum nutrient needs.” Admittedly, they offer substantial examples wherein various factors would influence these needs, and thus have led to the imposition of “margins of safety” to which the NRC requirements [1] used the term “allowances” rather than requirements, as additional allowances are “needed to provide for the contingencies which are inherent in the manufacture, transportation and use of poultry
Table 5. Broiler body, tissue and organ growth differences between a heritage line (University of Illinois, UrbanaChampaign) from 1940 versus Ross 708 broiler from 2007 (adapted from Schmidt et al. [19]) Breast Strain 1940 heritage 2007 Ross 708 2007 vs. 1940 1
Small intestine
BW gain (g/d)
g/d
AG1
mg/d
mg/g of BW
cm/d
cm/bird2
30.8 53.1 1.8
1.6 6.1 3.8
1.09 1.25
240 316 1.3
7 5 0.7
1.8 2.5 1.4
123 141 1.1
Allometric growth (AG) coefficient after 14 d of age. Length to a similar BW.
2
Heart
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improvements in growth that have occurred over time. Additionally, if one looks at composition of growth over time, the proportional growth of muscle and intestine far surpass that of other organs, such as the heart and skeleton. For example, Schmidt et al. [19] compared tissue growth differences between a heritage line (random bred since 1940) from the University of Illinois, Urbana-Champaign, and Ross 708 (late 2000s). Notably, the growth of the breast muscle was 3.8-fold greater, the small intestine was 1.14-fold longer, and growth of the heart was only 0.7 in the Ross 708 versus that in the heritage line (Table 5). This begs the question as to how nutrient needs, amino acids in particular, have shifted as composition of the carcass has changed. To that end, if one uses predictions for growth versus nutrient needs, comparisons can be made utilizing the NRC guidelines [3] and publications such as the Brazilian broiler nutrient requirement tables [20]. Notably, the Brazilian model predicts a 20% greater digestible Lys need by the broiler to 17 d or a common 2.1 kg of BW as compared with the NRC guidelines [3]. Much of this additional Lys need is directly attributable to compositional differences per unit of BW rather than only differences in intake or rate of BW growth to a common BW (Table 6). Similarly, Williams et al. [9] reported differences in tibia characteristics between a slow-
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Table 6. Predicted growth and digestible Lys requirement per NRC [3] versus Rostagno et al. [20] at 17 d of age and a common 2 kg of BW Reference NRC Rostagno et al. NRC Rostagno et al.
Age (d)
BW (kg)
FCR
Digestible Lys (%)
17 17 42 32
0.68 0.70 2.09 2.07
1.43 1.38 1.82 1.55
0.98 1.23 0.87 1.10
to or below their requirement (e.g., phosphorus), the variability in response of the population increases. Similarly, birds within the flock respond differently to a challenge, thus increasing this variation. This is of particular economic consideration, as substantial yearly improvements in performance (meat yield, egg production) continue beyond what we traditionally think of as the breakpoint. To further complicate issues, the literature is pervasive with different presentation and terminology related to requirements, including that of a breakpoint determined through broken-line analyses (optimum nutrient return per unit of nutrient input for a measured characteristic), a quadratic asymptote (maximum or minimum), or a percentage (e.g., 90 or 95%) of the asymptote. Either way, these measures average the response of the population, whereas, more times than not, the variance around that mean gets lost in interpretation. Regardless, the NRC committees are tasked with utilizing the best information available. This leads us to ask, “Why and in what circumstances would the variance matter?” Case in point would be related to that of skeletal and leg abnormalities and industry formulation targets for macrominerals and vitamin D3. Historically, the industry has supplemented vitamin D3 at concentrations well above what is typically reported as the requirement. For example, Edwards et al. [25] reported the vitamin D3 requirement of broilers for growth to be 275 IU/kg, for bone ash
Table 7. Broiler tibia growth and mineral characteristics between a slow and fast broiler strain (as adapted from Williams et al. [9]) Broiler strain Slow Fast
Tibia width (mm/kg of BW at 42 d)
Tibia length (mm/kg of BW at 42 d)
Tibia ash
Tibia
(%, 4 d)
(%, 42 d)
(% Ca)
(% P)
5.3 2.6
94.1 39.3
41 29
58 46
26.9 18.5
11.4 8.4
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feeds.” In today’s ingredient pricing environment, we likely can no longer afford this vague notion for unspecified margins of safety without a quantifiable performance or yield response to nutrient input variation. Thus, Ahmad and Roland [22] and Gous [23] have suggested that we rather should be discussing nutrient “responses” rather than requirements per se; encompassing considerations of marginal cost of ingredient or nutrient input versus marginal returns of product. This concept becomes rather complicated in our traditional view of nutrient requirement tables, as prior nutrient intake influences current and future performance responses. Furthermore, as the broiler market now has a different ending BW, optimization of these birds’ different ending BW and composition will take different nutrient response curves. Thus, modeling of nutrient responses based on the desired end product offers a more dynamic applicability than static requirements in tabular form. Part of this complexity is also due to (1) individual responses within a particular environment, (2) variation in nutrient delivery to the bird versus what was formulated, (3) variation in ingredient nutrient composition, and (4) feed management systems that include free choice or restricted intakes. The response from insufficiency to sufficiency becomes curvilinear, because we determine the response for a population, and not the individual. Work by Schinckel et al. [24] suggests that as birds are fed closer
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CONCLUSIONS AND APPLICATIONS
1. Much has changed with animal nutrition since the inception of NRC nutrient requirement publications. 2. Nevertheless, their tradition of scientific rigor and independence has allowed them to become benchmarks for the scientific, judicial, and regulatory communities domestically and abroad. 3. Substantial time has passed and scientific progress has been made since the ninth revised edition of the NRC Nutrient Requirements for Poultry in 1994. Of the 4 primary livestock species, the poultry
publication is the oldest revised edition, with beef being currently updated and dairy undergoing committee formation and financial organization (last revision in 2001), and swine having been recently updated in 2012. 4. Several challenges need to be faced if an update is to be made to the poultry NRC requirements beyond the need for substantial commitments of financial resources from all sources and volunteer time from scientists. 5. The first challenge is to find a consensus among industry and scientists that a new NRC guideline for poultry is needed.
REFERENCES AND NOTES 1. NRC. 1944. Recommended Nutrient Allowances for Poultry. 1st ed. Natl. Acad. Press, Washington, DC. 2. NRC. 1984. Nutrient Requirements of Poultry. 8th rev. ed. Natl. Acad. Press, Washington, DC. 3. NRC. 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC. 4. United States Government. 2011. 5 USC § 552: Public information; agency rules, opinions, orders, records, and proceedings. Accessed Jun. 11, 2014. http://www.gpo.gov/ fdsys/pkg/USCODE-2010-title5/pdf/USCODE-2010-title5partI-chap5-subchapII-sec552.pdf. 5. United States Government. 2009. 5 USC App. II § 1–15: Federal advisory committee act. Accessed Jun. 11, 2014. http://www.gpo.gov/fdsys/pkg/USCODE-2010-title5/ html/USCODE-2010-title5-app-federalad.htm. 6. USDA-National Institute of Food and Agriculture. 2014. Ongoing details regarding the activities and accomplishments of the National Animal Nutrition Program. Accessed June 4, 2014. http://nanp-nrsp-9.org. 7. Havenstein, G. B., P. R. Ferket, S. E. Scheidler, and B. T. Larson. 1994. Growth, livability, and feed conversion of 1991 vs 1957 broilers when fed “typical” 1957 and 1991 broiler diets. Poult. Sci. 73:1785–1794. 8. Havenstein, G. B., P. R. Ferket, and M. A. Qureshi. 2003. Carcass composition and yield of 1957 versus 2001 broilers when fed representative 1957 and 2001 broiler diets. Poult. Sci. 82:1509–1518. 9. Williams, B., S. Solomon, D. Waddington, B. Thorp, and C. Farquharson. 2000. Skeletal development in the meat-type chicken. Br. Poult. Sci. 41:141–149. 10. Ferket, P.R. 2003. Growth of toms improves substantially. Pages 38–48 in WATT Poultry USA, July 2003. Rockford, IL. 11. Dozier, W. A., III, M. T. Kidd, and A. Corzo. 2008. Amino acid responses of broilers. J. Appl. Poult. Res. 17:157–167. 12. Applegate, T., W. J. Powers, R. Angel, and D. Hoehler. 2008. Effect of amino acid formulation and acid supplementation on performance and nitrogen excretion in turkey toms. Poult. Sci. 87:514–520. 13. Lunden, T. 2009. Protein improves turkey gain. Feedstuffs 81:10–12.
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to be 503 IU/kg, for plasma Ca to be 552 IU/kg, and for rickets prevention to be 904 IU/kg; yet broiler and turkey diets routinely contain 2,000 to over 5,000 IU/kg. This over-supplementation is a partial reflection of a report by Yang et al. [26]. In that report, they evaluated 26 vitamin D3 supplements using a biological response in turkey poults of changes in femur ash content; the supplements elicited a range of bio-potencies of 40 to 134%. Thus, they recommended an oversupplementation of vitamin D3 by 3 to 4 times the requirement as an insurance factor. More recent evaluations of sources of vitamin D3 across the industry resulted in a reduced variation in a broiler bio-assay (86 to 118% [27]). This, coupled with much improved methods of chemical analyses, has greatly improved our confidence in the concentration and bio-potency of the vitamin received by our birds, but has not changed industry supplementation concentrations for vitamin D3 41 yr after that initial report on variable bio-potency of commercial D3 sources. Only under regulatory constraints have industry use concentrations changed (e.g., Europe). Industry has hesitated to reduce D3 concentrations as leg problems continue to be a concern. In recent years, the US broiler industry has increased the proportion of birds produced toward the heavy roasters market, and the weight of broilers has increased to maximize processing plant margins. With these increases in BW at processing, the reported incidence of late mortalities, most associated with gait and or leg abnormalities, has increased by 1 to 1.5%, resulting in substantial economic losses.
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22. Ahmad, H. A., and D. A. Roland Sr. 2003. Effect of method of feeding and feed formulation on performance and profitability of laying hens: An econometric approach. J. Appl. Poult. Res. 12:291–298. 23. Gous, R. M. 2014. Modeling as a research tool in poultry science. Poult. Sci. 93:1–7. 24. Schinckel, A. P., O. Adeola, and M. E. Einstein. 2005. Evaluation of alternative nonlinear mixed effects model of duck growth. Poult. Sci. 84:256–264. 25. Edwards, H. M., Jr., M. A. Elliot, S. Sooncharerynying, and W. M. Britton. 1994. Quantitative requirement for cholecalciferol in the absence of ultraviolet light. Poult. Sci. 73:288–294. 26. Yang, H. S., P. E. Waibel, and J. Brenes. 1973. Evaluation of vitamin D3 supplements by biological assay using the turkey. J. Nutr. 103:1187–1194. 27. Kasim, A. B., and H. M. Edwards Jr. 2000. Evaluation of cholecalciferol sources using broiler chick assays. Poult. Sci. 79:1617–1622.
Acknowledgments
This paper is a summation of concepts from a 2013 Poultry Science Association (PSA) symposium, entitled “Nutrient Requirement Evaluation and Publication for Poultry: US and Global Perspectives.” Presentations from that symposium are archived and accessible through the following PSA website: http://www.poultryscience.org/psa13/recordingsNREaPfPUaG.asp. This paper was previously presented at the 2014 Mid-Atlantic Nutrition Conference in Timonium, Maryland.
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