Animal Industry and Technology
Korean Society of Animal Science and Technology
REVIEW ARTICLE

Advances of nutritional technologies and science in pig production

Sung Woo Kim*https://orcid.org/0000-0003-4591-1943, Zixiao Denghttps://orcid.org/0009-0008-7731-6149, Hyunjun Choihttps://orcid.org/0000-0002-5874-2328
Department of Animal Science, North Carolina State University, Raleigh, NC 27695, USA
*Corresponding author: Sung Woo Kim Department of Animal Science, North Carolina State University, Raleigh, NC 27695, USA Tel: +1-919-513-1494 E-mail: sungwoo_kim@ncsu.edu

© Copyright 2024 Korean Society of Animal Science and Technology. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: Apr 02, 2024; Revised: Apr 14, 2024; Accepted: May 14, 2024

Published Online: Jun 30, 2024

Abstract

Advances in nutritional technologies and science greatly improved the growth efficiency of pigs by about 30% during the last 40 years. Genetic improvement for lean gain has provided the fundamental basis to increase market weight improving production efficiency. Advances in nutritional technology and science allowed pigs to express their maximal potential for growth. Selected nutritional technologies and science with significant contribution to this improvement could include the concepts and implication of corn and soybean-meal based feeds, phase feeding program, investigation and implication of ideal protein with increased availability of supplemental amino acids, evaluation of ileal digestibility and energy systems (metabolizable energy and net energy; ME and NE) of feedstuffs, fermentation technology allowing effective production of feed additives replacing the use of antimicrobial growth promotors.

Keywords: Feed additives; Ideal protein; Nutritional technology; Phase feeding; Pigs

INTRODUCTION

The advances of technical experience and scientific knowledge in nutrition greatly improved the efficiency of animal agriculture in recent decades. In the area of pig production, enough examples and milestones can be introduced to support this statement.

Over the last 40 years, the efficiency and productivity of pig production have been improved 30.9% and 27.3% for gain to feed ratio and market weight, respectively (Table 1). Improvement in genetic potential for lean gain has provided the fundamental basis to increase market weight improving production efficiency. Nutritional technology and science have supported the pigs to express their genetic potential.

Table 1. Changes in growth performance and lean (%) of growing-finishing pigs between 1980s and 2020s
Item 1980s1) 2020s2) % Change3)
Growth performance4)
Average daily gain (kg/d) 0.79 0.825) 4.0
Average daily feed intake (kg/d) 2.71 2.156) −20.6
Gain to feed ratio 0.29 0.38 30.9
Duration (d) 99.3 117.3 18.1
Market weight (kg) 100.0 127.3 27.3
Lean (%, at market weight) 58.1 56.5 −2.7

Data were based on 3 references [4648].

Data were based on 2 references [49,50].

The percentage changes were determined in the 2020s relative to the 1980s.

Averaged initial and final body weight ranged from 22 to 100 kg in 1980s and 27.6 to 127 kg in 2020s, respectively.

The ADG in 2020s was adjusted to compare the ADG in 1980s using the coefficient 0.9624 data adapted from Duarte et al. [51].

The ADFI in 2020s was adjusted to compare the ADG in 1980s using the coefficient 0.9373 data adapted from Duarte et al. [51].

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In this article, some of selected milestones in nutritional technology and science with significant contributions to pig production are listed, introduced, and discussed.

SELECTED MILESTONES IN NUTRITIONAL TECHNOLOGY AND SCIENCE CONTRIBUTED TO PIG PRODUCTION

Corn and soybean meal-based feeds

Corn and cereal grains have largely been used in feeding livestock including pigs for their high energy content. Among these, corn has been most popular for its higher energy contents and affordability than other cereal grains. Protein, however, is not sufficient in corn to meet the requirement for efficient growth of pigs. Corn protein specifically low in lysine and tryptophan that are key essential amino acids for pigs. Various protein supplements, therefore, should have been added to corn for the efficient growth of pigs.

Soybeans have long been used as human foods. Oil extraction for cooking has been one of major use of soybean meals. After the extraction of oil, the left-over is roasted and dried as soybean meal that is high in protein especially key essential amino acids such as lysine and tryptophan. The term, soybean meal, referring cooked meal of defatted soybeans is known to be first coin by Thompson & Morgan (1912) and the use of soybean meal in feeding pigs has been evaluated [1]. Soybean meal is particularly important because lysine and tryptophan are low in protein from corn. Thus, a combinational use of corn and soybean meal has provided ideally balanced essential amino acids for the efficient growth of pigs. Corn and soybean meal-based feeds have been practiced in feeding pigs since 1960’s and has been a golden standard in feeding pigs since then [2,3].

Phase feeding

For the efficient growth, feeds should contain a sufficient amount of nutrients required by pigs. Nutrient requirements, however, are not consistent in pigs with various growth stages (age) and physiological status. With increasing feed intake, nutrient requirement (contents in feeds) reduces as pigs grow. Therefore, in feeding pigs, multiple feeds are prepared gradually reducing nutrient contents as pigs grow. Reduction of nutrient requirement as pigs grow is continuous process, but in practice, feeds are prepared by reducing nutrient content in multiple phases. Considering practicality, a limited number of phases is used. For nursery pigs (from weaning to around 20–25 kg body weight), typically 2 to 4 phases have been used in pig production. For growing and finishing pigs until marketing, typically 4 to 7 phases have been used in pig production. Implementing the concept of phase feeding greatly improved the efficiency of pig production, reduced feed costs, and reduced nutrient waste through manure. The number of phases depends on ability of pig producers. Increasing the number of phases will improve the efficiency of pig growth by providing nutrients as close as requirements. However, increasing the number of phases could increase the feed cost and production cost. With recent technology of real time mixing, it is possible that phase feeding program could further develop to precision feeding of pigs providing feeds with nutrients meeting requirements of pigs individually.

Ideal protein

In pig production, lean gain (increase of body protein) is the primary target of profit. Protein synthesis is predetermined based on genetic code resulting in building a sequence of amino acids. There are specific compositions of amino acids needed for lean gain depending on stage of growth and physiological status of pigs. There have been tremendous research efforts to identify ideal ratios among amino acids (so called ‘ideal protein’ especially among essential amino acids) for lean growth of pigs. Formulating feeds based on ideal protein concept minimizes the amount of unutilized amino acids and thus also minimizing unneeded amino acid catabolism. Appling ideal protein in feeding pigs has also reduced the use of protein supplements resulting in reduced crude protein in feeds and thus reducing nitrogen waste through manure. Increased availability of feed grade supplemental amino acids greatly encouraged nutritionists to apply ideal protein in feed formulation. For growing pigs, ideal protein is less variable by growth stages [4], whereas ideal protein dynamically changes for sows depending on protein needs for fetal tissues gain, mammary tissue gain, milk production, and contributions from maternal lean tissue mobilization [59] (Table 2). The milestone research investigating optimum dietary amino acid pattern and ideal protein was initiated by two research teams at Rowett Research Institute (Bucksburn, Aberdeen, UK) led by Dr. Fuller since 1989 [10,11] and at University of Illinois (Urbana, IL, USA) led by Dr. Baker since 1992 [12].

Table 2. Dynamic ideal protein for sows during gestation [7,9] and lactation [7,52]
Ratio to lysine (%) True ileal digestible amino acids
Lysine Threonine Valine Leucine Isoleucine
Gestation
D 0 to d 60 of gestation 100 79 65 88 59
D 60 of gestation to farrowing 100 71 66 95 56
Lactation
0% (maternal tissue mobilization) 100 59 77 115 59
20% (maternal tissue mobilization) 100 61 77 116 59
40% (maternal tissue mobilization) 100 63 78 118 59
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The concept of ideal protein has provided a fundamental basis of establishing nutrient requirements for pigs and feed formulations. Increased availability of feed grade supplemental amino acids has been critical for the successful implementation of ideal protein in feed formulations.

Supplemental amino acids

As feedstuffs contain proteins with fixed amino acid composition, it is not possible to perfectly provide ideally balance amino acids by mixing various feedstuffs. It is mostly possible to match the requirements of 2 to 4 key essential amino acids but others would suffice the requirements.

Pure (or crystalline) amino acids have been introduced and produced in food application since early 1900. It is produced by bacterial fermentation followed by purification process. Similar technology has been applied to produce feed grade amino acids. These amino acids are collectively called ‘supplemental amino acids’ whist other terms including ‘crystalline amino acids’ and ‘synthetic amino acids’ have also been used.

Feed grade lysine became available from a large-scale bacterial fermentation since 1960s. Production of lysine allowed the reduced use of protein supplements (such as soybean meal) in pig feeds. Use of lysine at 0.1% would allow to reduce soybean meal by 4% unit in typical pig feeds (as an example of the reduction of soybean meal from 24% to 20%: 4%-unit reduction). In the meantime, methionine has been produced through chemical process as bacterial fermentation would be poorly efficient to produce methionine containing sulfur. Methionine has well been used in pig feeding whereas poultry production is the major user of feed grade methionine. Soon after the introduction of lysine, additional feed grade amino acids have been produced including threonine and tryptophan. Availability of these 4 feed-grade amino acids tremendously reduced the use of protein supplements resulting in reducing crude protein in feeds at least by 6% unit (compared to no use of supplemental amino acids). More recently, feed grade valine (since 2008), arginine (since 2014), isoleucine (since 2015), and histidine (since 2017) have been available allowing further reduction of crude protein in pig feeds whist meeting amino acid requirements.

Currently, at least 8 feed grade supplemental amino acids are available and extensively used in pig production. The global use (demand) of lysine was over 2.5 million t in 2023 with 3-fold increase since 2005 (Fig. 1). Supplemental amino acids allowed the reduced use of protein supplements, reduction of crude protein in feeds, reduced feed cost, and reduced nitrogen excretion through manure without compromise in production efficiency.

ait-11-1-45-g1
Fig. 1. Global lysine use (1,000 ton).
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Evaluation of ileal digestibility

A proper supply of amino acids [13] in adequate quantities is critical for the maintenance and maximal growth of pigs. Amino acid requirements in pigs and amino acid composition in feedstuffs have been changed to digestible amino acid contents for pigs. The total tract digestibility of amino acids in pigs have measured using the fecal index method, first suggested by Kuiken et al. [14]. However, the total tract digestibility method has limitations that undigested amino acids can be broken down by fermentation by microorganisms in the large intestine, resulting in an overestimation of digestibility of amino acids [15,16].

Ileal cannulation technique in pigs has been adapted to measure accurate ileal digestibility of amino acids in pigs [17]. Ileal cannulation technique allows for the direct collection of ileal digesta, minimizing microbial fermentation influence on amino acids, as well as reducing the need to sacrifice pigs for ileal digesta sample collection. Ileal digestibility can be divided into apparent, true, and standardized ileal digestibility (SID). Apparent ileal digestibility (AID) reflects both non-digested dietary amino acids and total endogenous losses of amino acids, which do not result in the net disappearance of amino acids from the small intestine prior to the distal ileum. The major concern with using AID is that AID values lack additivity in mixed diets, especially feedstuffs with lower amino acid content due to high proportion of the endogenous losses to undigested amino acids [18]. To overcome the additivity issue and to supply a proper quantity of amino acids for pigs, total endogenous losses of amino acids can be excluded to determine the true ileal digestibility (TID) of feedstuffs [19,20].

The TID accounts for total endogenous losses of amino acids, including specific and basal endogenous losses. However, measuring total endogenous losses of amino acids is challenging due to the varying levels of specific endogenous losses of amino acids caused by different feedstuffs. This challenge makes it difficult to apply TID to the wide range of feedstuffs commonly used in pig feeds, and TID is less accurate for ensuring additivity in mixed diets.

To address these challenges, Mariscal Landin [21] first introduced the term SID. This method involves collecting digesta at the end of the ileum and correcting for only basal endogenous losses of amino acids [22,23]. For measuring basal endogenous losses of amino acids, N-free diets or diets containing protein source with an assumed 100% digestible were provided to pigs. Those methods to get basal endogenous losses of amino acids for SID were relatively simple, less costly, and less variable to determine the endogenous losses of amino acids. Therefore, the SID has become the most appropriate method for evaluating the digestibility of amino acids based on current research findings [24].

Evaluation of metabolizable energy (ME) and net energy (NE)

Energy is not a nutrient, but energy is crucial for pigs to utilize nutrients. Energy content in feeds has an impact on the voluntary feed intake of pigs, consequently energy should be considered when determining the nutrient requirements of pigs. Pigs derive energy from digesting and absorbing carbohydrates, fats, and proteins from feeds, which are oxidized to support the maintenance, growth, and reproduction of pigs. The total gross energy (GE) in feeds undergoes digestion, absorption, oxidation, and excretion processes, with only the remaining energy being available to pigs. The available energy is categorized into digestible energy (DE), metabolizable energy (ME), and net energy (NE) [25].

The DE is the total energy consumed minus the energy lost in feces, representing the energy absorbed by the animal, which is easy to measure and has been widely used to express energy requirements and the energy content of feedstuffs for pigs. ME is the DE minus the energy lost in gases and urine. In pigs, the energy lost in gases is minimal (0.1% to 3% of DE), thus, ME primarily considers urinary energy losses. However, ME does not account for heat increment. Heat increment is the heat produced by the digestion and metabolism of nutrients and fermentation in the gastro-intestinal tract of pigs [26]. ME system can also lead to overestimating the energy value of high-fiber and high-protein feedstuffs and underestimating that of high-fat and high-starch feedstuffs [27]. Fats and starch produce less heat increment, whereas proteins and dietary fibers produce more heat increment [28]. Consequently, the high production of adenosine triphosphate (ATP) in fats and glucose is more likely stored as lipids compared with amino acids and dietary fiber [29]. Thus, NE system can provide accurate available energy to pigs and have gradually recognized and used in pig production. The NE system have allowed to increase in the use of alternative feedstuffs such high dietary fiber coproducts, to reduce protein contents in diets with increasing amino acid supplementation in feeds, and to mitigate environmental pollution. Despite theoretical advantages of NE system, the system requires ongoing refinement to address these issues [30]. This is because NE system had challenges, such as difficulty for accurately measuring maintenance energy requirements or fasting heat production (NEm), growth and reproduction energy requirements (NEp), and changes in energy metabolism by certain condition [31,32].

Fermentation technology

With the rapid development of animal agriculture, demands for feed additives, such as enzymes, amino acids, probiotics, and postbiotics have increased dramatically over the last decades. Properly using these feed additives improve swine production efficiency and the profitability of producer. Fermentation plays a key role in the production of feed additives in the swine industry.

Fermentation is a process that the substance is broken down by microorganisms. Enzyme products is typically produced by using the microorganisms with providing suitable nutrient and controlled conditions, then the end products, enzymes, are subsequently isolated through centrifugation or filtration [33]. Majority of enzyme producer use submerged fermentation technology because of the scalability, better control of environmental conditions, and high productivity. However, solid-state fermentation is getting more attention by the researchers due to the advantages [34]. Compared to liquid fermentation, solid-state fermentation has advantages such as lower wastewater generation, higher product stability, lower energy consumption during fermentation, and ease to transfer the end products [35]. Fermentation is becoming one of the most dominant methods to produce amino acids due to the cost-efficient and sustainable production. Modern technologies, such as gene modification and genome analysis, help the industry to improve the capacity of the strain producing enzymes [36]. In addition, innovative separation techniques, such as the nanofiltration membranes, can be used to reduce the cost of downstream processing [13]. The conventional batch fermentation is widely used in probiotics production. Cell viability is an important parameter to evaluate the quality of probiotics. Several technologies have been studied to improve cell viability, such as sublethal stresses during fermentation [37]. Postbiotics are bioactive compounds produced by beneficial microorganisms or released by bacterial lysis that exert some benefits to the consumer. Lactic acid bacteria is considered the common bacteria producing postbiotics [38].

Beside feed additives, feedstuffs or feeds can be improved by using fermentation technology. Fermentation not only helps to provide high-quality feedstuffs or feeds but also aids in the breakdown of toxins, anti-nutritional compounds, and harmful microorganisms present in the raw materials [39]. There are two main fermentation technologies for feedstuffs or feeds, including liquid fermentation, and solid-state fermentation. The former involves mixing feed and water in certain proportions in a tank and storing them at a certain temperature for a period of time. In the initial stage of fermentation, the characteristics include low levels of lactic acid bacteria, yeast, and lactate, with a high pH, and significant proliferation of enterobacteria. The second stage reaches a stable state, characterized by high levels of lactic acid bacteria, yeast, and lactate, low pH, and a reduction in the number of enterobacteria [40]. Yeast (Saccharomyces cerevisiae) and fungi (Aspergillus oryzae and Aspergillus niger) are typically involved in the solid-state fermentation system to facilitate the fermentation processes because of less water used in this system [41]. These two microorganisms not only reduce oxygen in the fermentation environment during the early stage, but also release a large amount of enzymes (e.g., cellulase, phytase), vitamins, and growth factors for microorganisms. In addition to fungi, bacteria are also used for solid-state fermentation, including Lactobacillus and Bacillus. Furthermore, different enzymes are used either alone or in combination with microorganisms to promote fermentation process, including proteases, carbohydrase (cellulase, xylanase), phytase. Some of these solid-state fermentation products are added to swine diet to replace high-cost feedstuffs such as fishmeal, blood plasma, and poultry meal without negatively affecting growth performance of animals [42].

Bioactive compounds as feed additives

One of the most effective feed additives (non-nutritive supplements) would be antimicrobial growth promotors (AGP, antibiotics) with consistent improvement in weight gain and growth efficiency [43]. Due to concerns with occurrence of bacterial resistance to antibiotics, their non-therapeutic uses in animal feeding have been restricted and banned in several countries including the EU (2006), Korea (2011), China (2016), and the USA (2017). Restricting the use of AGP triggered the efforts of developing alternative feed additives and provided opportunities for their use in pig feeds. Some of successful feed additives possess antimicrobial properties mimicking the function of AGP and also those improving intestinal health to be ready for pathogenic challenges. Feed additives with antimicrobial properties include phytogenics (or phytobiotics including herbal extracts and essential oils), medium chain fatty acids (including lauric acid and myristic acid), acidifiers (including formic acid and benzoic acid), and selected minerals (including ZnO and CuSO4). Feed additives with properties maintaining good intestinal health include prebiotics (such as fructose oligosaccharides, galactose oligosaccharides, and mannose oligosaccharides), probiotics (mostly Bacillus spp, and Lacobacillus spp), postbiotics (bacterial cell walls, and yeast cell components), and feed enzymes (with properties to hydrolyze antinutritional compounds and allergenic compounds). There are enormous research efforts have been poured in the evaluation of feed additives. In 2022 and 2023, about 25% to 35% of 1,000 research presentations made in conferences held in the USA were directly related to intestinal health evaluating feed additives replacing the role of AGP [44,45].

CONCLUSION

The efficiency and profitability of pig production have been improved greatly over last decades. In this article, selected nutritional technologies and science advances improving the efficiency of pig production have been reviewed. Introduction of the concepts and implication of corn and soybean-meal based feeds and phase feeding contributed to structure nutritional management of pigs. Research advances to characterized ideal protein with increased availability of supplemental amino acids greatly improved production efficiency, reduced feed cost, reduced nutrient waste, and improved health of pigs. Advances in nutritional technologies evaluating ileal digestibility and energy systems (ME and NE) have expanded opportunities to implement precision feeding and also to use new feedstuffs and coproducts. Enhanced development of fermentation technology allowed effective production of feed additives including feed enzymes, probiotics, and postbiotics and also allowed effective processing of feedstuffs to improve digestibility and to eliminate antinutritional compounds and allergens. Restriction and ban of the use of AGP have opened opportunities of these feed additives and processed feedstuffs especially for young pigs to maintain intestinal health and therefore improve production efficiency of pig production.

Competing interests

No potential conflict of interest relevant to this article was reported.

Funding sources

Not applicable.

Acknowledgements

Not applicable.

Availability of data and material

Upon reasonable request, the datasets of this study can be available from the corresponding author.

Authors’ contributions

Conceptualization: Kim SW.

Data curation: Kim SW, Deng Z, Choi H.

Formal analysis: Kim SW, Deng Z, Choi H.

Investigation: Kim SW, Deng Z, Choi H.

Writing - original draft: Kim SW, Deng Z, Choi H.

Writing - review & editing: Kim SW, Deng Z, Choi H.

Ethics approval and consent to participate

This article does not require IRB/ IACUC approval because there are no human and animal participants.

REFERENCES

1.

E HaselhoffSwine fattening experiments with soybean mealFühlings Landwirtschaftliche Ztg19126140114

2.

W ShurtleffA AoyagiHistory of soybean crushing: soy oil and soybean meal (980–2016): extensively annotated bibliography and sourcebookLafayette, CASoyinfo Center2016

3.

J Smith JrAJ ClawsonER BarrickEffect of ratio of protein from corn and soybean meal in diets of varying total protein on performance, carcass desirability and diet digestibility in swineJ Anim Sci1967267528

4.

National Research Council [NRC]Nutrient requirements of swine11th edWashington, DCNational Academies Press2012

5.

F JiG WuJR Blanton JrSW KimChanges in weight and composition in various tissues of pregnant gilts and their nutritional implicationsJ Anim Sci20058336675

6.

SW KimWL HurleyIK HanRA EasterChanges in tissue composition associated with mammary gland growth during lactation in sowsJ Anim Sci19997725106

7.

SW KimWL HurleyG WuF JiIdeal amino acid balance for sows during gestation and lactationJ Anim Sci200987E12332

8.

RL McPhersonF JiG WuJR Blanton JrSW KimGrowth and compositional changes of fetal tissues in pigsJ Anim Sci200482253440

9.

SW KimRecent advances in sow nutritionRev Bras Zootec20103930310

10.

MF FullerR McWilliamTC WangLR GilesThe optimum dietary amino acid pattern for growing pigs: 2. requirements for maintenance and for tissue protein accretionBr J Nutr19896225567

11.

TC WangMF FullerThe optimum dietary amino acid pattern for growing pigs: 1. experiments by amino acid deletionBr J Nutr1989627789

12.

TK ChungDH BakerIdeal amino acid pattern for 10-kilogram pigsJ Anim Sci199270310211

13.

J EckerT RaabM HarasekNanofiltration as key technology for the separation of LA and AAJ Membr Sci201238938998

14.

KA KuikenCM LymanS DieterichM BradfordM TrantAvailability of amino acids in some foodsJ Nutr19483635968

15.

JHG HolmesHS BayleyPA LeadbeaterFD HorneyDigestion of protein in small and large intestine of the pigBr J Nutr19743247989

16.

WC SauerSC StothersGD PhillipsApparent availabilities of amino acids in corn, wheat and barley for growing pigsCan J Anim Sci19775758597

17.

RA EasterTD Tanksley JrA technique for re-entrant ileocecal cannulation of swineJ Anim Sci1973361099103

18.

MZ FanWC SauerRT HardinKA LienDetermination of apparent ileal amino acid digestibility in pigs: effect of dietary amino acid levelJ Anim Sci19947228519

19.

CFM de LangeWB SouffrantWC SauerReal ileal protein and amino acid digestibilities in feedstuffs for growing pigs as determined with the 15N-isotope dilution techniqueJ Anim Sci19906840918

20.

MZ FanWC SauerDetermination of true ileal amino acid digestibility in feedstuffs for pigs with the linear relationships between distal ileal outputs and dietary inputs of amino acidsJ Sci Food Agric19977318999

21.

G Mariscal LandinFactors affecting the digestive utilisation of amino acids in the pig [Ph.D. dissertation]RennesUniversity of Rennes1992

22.

C JondrevilleJ Van den BroeckeF GatelS Van CauwenbergheIleal digestibility of amino acids in feedstuffs for pigsParisEurolysine-ITCF1995

23.

CM NyachotiCFM de LangeBW McBrideH SchulzeSignificance of endogenous gut nitrogen losses in the nutrition of growing pigs: a reviewCan J Anim Sci19977714963

24.

HH SteinB SèveMF FullerPJ MoughanCFM de LangeInvited review: amino acid bioavailability and digestibility in pig feed ingredients: terminology and applicationJ Anim Sci20078517280

25.

RW SeerleyRC EwanAn overview of energy utilization in swine nutritionJ Anim Sci19835730014

26.

LJ KoongJA NienaberJC PekasJT YenEffects of plane of nutrition on organ size and fasting heat production in pigsJ Nutr1982112163842

27.

J NobletH FortuneXS ShiS DuboisPrediction of net energy value of feeds for growing pigsJ Anim Sci19947234454

28.

D SauvantJM PerezG TranTablas de composicion y de valor nutritivo de las materias primas destinadas a los animales de interés ganadero (Cerdos, aves, bovinos, ovinos, caprinos, conejos, caballos y peces)MadridMundi Prensa2004

29.

JL BlackModelling energy metabolism in the pig - critical evaluation of a simple reference modelPJ MoughanMWA VerstegenMI Visser-ReyneveldModeling growth in the pigWest Lafayette, INPurdue University Press199587102In: editors p.

30.

DY KilBG KimHH SteinFeed energy evaluation for growing pigsAsian-Australas J Anim Sci201326120517

31.

S BirkettK de LangeLimitations of conventional models and a conceptual framework for a nutrient flow representation of energy utilization by animalsBr J Nutr20018664759

32.

N QuiniouS DuboisJ NobletEffect of dietary crude protein level on protein and energy balances in growing pigs: comparison of two measurement methodsLivest Prod Sci1995415161

33.

SW KimBio-fermentation technology to improve efficiency of swine nutritionAsian-Australas J Anim Sci20102382532

34.

A PandeyP SelvakumarCR SoccolP NigamSolid state fermentation for the production of industrial enzymesCurr Sci19997714962

35.

A PandeySolid-state fermentationBiochem Eng J200313814

36.

W LeuchtenbergerK HuthmacherK DrauzBiotechnological production of amino acids and derivatives: current status and prospectsAppl Microbiol Biotechnol20056918

37.

C LacroixS YildirimFermentation technologies for the production of probiotics with high viability and functionalityCurr Opin Biotechnol20071817683

38.

M MoradiSA KoushehH AlmasiA AlizadehJT GuimarãesN Yılmazet al.Postbiotics produced by lactic acid bacteria: the next frontier in food safetyCompr Rev Food Sci Food Saf2020193390415

39.

KJ HongCH LeeSW KimAspergillus oryzae GB-107 fermentation improves nutritional quality of food soybeans and feed soybean mealsJ Med Food200474305

40.

N CanibeBB JensenFermented and nonfermented liquid feed to growing pigs: effect on aspects of gastrointestinal ecology and growth performanceJ Anim Sci200381201931

41.

RR SinghaniaAK PatelCR SoccolA PandeyRecent advances in solid-state fermentationBiochem Eng J200944138

42.

Z DengME DuarteSW KimEfficacy of soy protein concentrate replacing animal protein supplements in mucosa-associated microbiota, intestinal health, and growth performance of nursery pigsAnim Nutr20231423548

43.

GL CromwellWhy and how antibiotics are used in swine productionAnim Biotechnol200213727

44.

HY KimJO MoonSW KimDevelopment and application of a multi-step porcine in vitro system to evaluate feedstuffs and feed additives for their efficacy in nutrient digestion, digesta characteristics, and intestinal immune responsesAnim Nutr20241726582

45.

SW KimA GormleyKB JangME DuarteCurrent status of global pig production: an overview and research trendsAnim Biosci20243771929

46.

KD HaydonTD Tanksley JrDA KnabePerformance and carcass composition of limit-fed growing-finishing swineJ Anim Sci198967191625

47.

RG Shields JrDC MahanEffect of protein sequences on performance and carcass characteristics of growing-finishing swineJ Anim Sci19805113406

48.

GW TibbettsRW SeerleyHC McCampbellPoultry offal ensiled with Lactobacillus acidophilus for growing and finishing swine dietsJ Anim Sci19876418290

49.

KF CobleJM DeRoucheyMD TokachSS DritzRD GoodbandJC WoodworthEffects of withdrawing high-fiber ingredients before marketing on finishing pig growth performance, carcass characteristics, and intestinal weightsJ Anim Sci20189616880

50.

MB MenegatSS DritzMD TokachJC WoodworthJM DeRoucheyRD GoodbandPhase-feeding strategies based on lysine specifications for grow-finish pigsJ Anim Sci202098skz366

51.

ME DuarteW ParnsenS ZhangMLT AbreuSW KimLow crude protein formulation with supplemental amino acids for its impacts on intestinal health and growth performance of growing-finishing pigsJ Anim Sci Biotechnol20241555

52.

SW KimDH BakerRA EasterDynamic ideal protein and limiting amino acids for lactating sows: the impact of amino acid mobilizationJ Anim Sci200179235666