Standardized ileal digestible valine:lysine dose response effects in 25- to 45-kg pigs under commercial conditions

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1 Stndrdized ilel digestible vline:lysine dose response effects in 25- to 45-kg pigs under commercil conditions Mrcio A. D. Gonçlves, Mike D. Tokch, Steve S. Dritz,,1 Nor M. Bello, Kevin J. Touchette, $ Robert D. Goodbnd, Joel M. DeRouchey, nd Json C. Woodworth Deprtment of Dignostic Medicine/Pthobiology, College of Veterinry Medicine, Mnhttn, KS 66506; Deprtment of Animl Sciences nd Industry, College of Agriculture, Mnhttn, KS 66506; Deprtment of Sttistics, College of Arts nd Sciences, Mnhttn, KS ; $ Ajinomoto Hertlnd Inc., Chicgo, IL ABSTRACT: Two experiments were conducted to estimte the stndrdized ilel digestible vline:- lysine (SID Vl:Lys) dose response effects in 25- to 45-kg pigs under commercil conditions. In experiment 1, totl of 1,134 gilts (PIC ), initilly 31.2 kg ± 2.0 kg body weight (BW; men ± SD) were used in 19-d growth tril with 27 pigs per pen nd seven pens per tretment. In experiment 2, totl of 2,100 gilts (PIC ), initilly 25.4 ± 1.9 kg BW were used in 22-d growth tril with 25 pigs per pen nd 12 pens per tretment. Tretments were blocked by initil BW in rndomized complete block design. In experiment 1, there were totl of six dietry tretments with SID Vl t 59.0, 62.5, 65.9, 69.6, 73.0, nd 75.5% of Lys nd for experiment 2 there were totl of seven dietry tretments with SID Vl t 57.0, 60.6, 63.9, 67.5, 71.1, 74.4, nd 78.0% of Lys. Experimentl diets were formulted to ensure tht Lys ws the second limiting mino cid throughout the experiments. Initilly, liner mixed models were fitted to dt from ech experiment. Then, dt from the two experiments were combined to estimte dose-responses using broken-line liner scending (BLL) model, broken-line qudrtic scending (BLQ) model, or qudrtic polynomil (QP). Model fit ws compred using Byesin informtion criterion (BIC). In experiment 1, ADG incresed linerly (P = 0.009) with incresing SID Vl:Lys with no pprent significnt impct on G:F. In experiment 2, ADG nd ADFI incresed in qudrtic mnner (P < 0.002) with incresing SID Vl:Lys wheres G:F incresed linerly (P < 0.001). Overll, the best-fitting model for ADG ws QP, whereby the mximum men ADG ws estimted t 73.0% (95% CI: [69.5, >78.0%]) SID Vl:Lys. For G:F, the overll best-fitting model ws QP with mximum estimted men G:F t 69.0% (95% CI: [64.0, >78.0]) SID Vl:Lys rtio. However, 99% of the mximum men performnce for ADG nd G:F were chieved t, 68% nd 63% SID Vl:Lys rtio, respectively. Therefore, the SID Vl:Lys requirement rnged from73.0% for mximum ADG to 63.2% SID Vl:Lys to chieve 99% of mximum G:F in 25- to 45-kg BW pigs. Key words: mino cid rtio, growth, growing pig, lysine, vline The Author(s) Published by Oxford University Press on behlf of the Americn Society of Animl Science. All rights reserved. For permissions, plese e-mil: journls.permissions@oup.com. J. Anim. Sci : doi: /js/skx059 INTRODUCTION Vline (Vl) is commonly considered to be the fifth limiting mino cid fter Trp in corn-soyben 1 Corresponding uthor: dritz@vet.ksu.edu Received September 30, Accepted December 12, mel bsed diets for finishing pigs (Figuero et l., 2003). Yet, Vl cn esily become limiting in diets supplemented with feed-grde mino cids, such s lysine (Lys), Met, Thr, nd Trp. However, there is limited dt chrcterizing the Vl requirement in growing pigs. In fct in the most recent edition of the NRC, there were no studies summrized in the growing pig tht were reported with greter 591

2 592 Gonçlves et l. thn 27 kg finl body weight (BW). Also, following prcticl recommendtion to express mino cid requirement is s rtio to Lys (Stein et l., 2007), few studies hve ttempted to define specific point estimte for the requirement of Vl:Lys in pigs (Lewis nd Nishimur, 1995; Wguespck et l., 2012). In fct, the NRC (2012) published single overll stndrdized ilel digestible (SID) Vl:Lys requirement of 65% for 25- to 45-kg pigs. Yet, it is possible tht Vl requirements to optimize different mesurements of performnce such s ADG, G:F, or economics my vry substntilly s hs been shown for other AA (Gonçlves et l., 2015). Finlly, recent evidence suggests tht the SID Vl:Lys requirement my be greter thn 65% if broder rnge of BW in growing pigs is considered (Liu et l. 2015; Soumeh et l., 2015). Therefore, the objective of these studies ws to estimte ADG nd G:F in 25- to 45-kg pigs fed incresing dietry SID Vl:Lys under commercil conditions. Also, our objective ws to estimte the mximum or brekpoints for SID Vl:Lys rtio nd describe confidence intervls round these estimtes. MATERIALS AND METHODS Generl The Knss Stte University Institutionl Animl Cre nd Use Committee pproved the protocols used in these experiments. Ech experiment ws conducted in different commercil reserch-finishing brn in Minnesot. Both brns were nturlly ventilted nd double-curtin-sided nd pens hd completely sltted flooring nd deep pits for mnure storge. In experiment 1, pens were equipped with four-hole stinless steel dry self-feeder (Thorp Equipment, Thorp, WI) nd cup wterer. In experiment 2, ech pen ws equipped with three-hole stinless steel dry self-feeder (Thorp Equipment) nd cup wterer. Both fcilities were equipped with computerized feeding system (FeedPro; Feedlogic Corp., Willmr, MN) tht delivered nd recorded dily feed dditions. During the experiments, pigs hd d libitum ccess to feed nd wter. In experiment 1, totl of 1,134 gilts (PIC ), initilly 31.2 kg ± 2.0 kg BW (men ± SD) were used in 19-d growth tril with 27 pigs per pen (0.62 m 2 /pig) nd seven pens per tretment. In experiment 2, totl of 2,100 gilts (PIC ), initilly 25.4 ± 1.9 kg BW (men ± SD) were used in 22-d growth tril with 25 pigs per pen (0.67 m 2 /pig) nd 12 pens per tretment. In both experiments, pens were blocked by initil BW nd dietry tretments were rndomly ssigned to pens within ech block in rndomized complete block design. In experiment 1, there were six dietry tretments with dietry SID Vl t 59.0, 62.5, 65.9, 69.6, 73.0, nd 75.5% of Lys. For experiment 2, there were seven dietry tretments with SID Vl t 57.0, 60.6, 63.9, 67.5, 71.1, 74.4, nd 78.0% of Lys fed in mel form. In both experiments, the intermedite Vl:Lys rtios were obtined by blending different proportions of source diets consisting of low nd high Vl:Lys rtios (Tbles 1 nd 2 for experiments 1 nd 2, respectively). The NRC (2012) model ws used to estimte the Lys requirement of gilts t the expected BW t the end of ech experiment using the respective net energy per kg used in ech experiment. All other model prmeters were kept s defult. The SID Lys s percentge of the diet ws reduced by 0.10 percentge points below the requirement t the expected BW by end of experiment to ensure tht Lys ws the second limiting mino cid throughout the experiment. This specifiction ws bsed on results from preliminry study performed in the sme fcility nd with the sme pigs s those used in experiment 1 (Gonçlves et l., 2015). This experiment indicted tht diets formulted 0.10 percentge units below the SID Lys requirement estimted by NRC (2012) t the end of the experiment s weight rnge would ensure pigs were below the Lys requirement. Diet Smpling nd Anlysis Five representtive smples of corn, soyben mel, nd DDGS were collected weekly for 5 wk nd nlyzed in duplicte for totl AA (except Trp; method ; AOAC Int., 2012), Trp (method 13904:2005; ISO, 2005), nd CP (method ; AOAC Int., 2012) by Ajinomoto Hertlnd Inc. (Chicgo, IL) for ech experiment. The verges of these vlues were then used in diet formultion. Other nutrients nd SID AA digestibility coefficient vlues used for diet formultion were obtined from NRC (2012). Rtios of other essentil mino cids were evluted in the finl diet formultions s well s ensuring tht enough nonessentil mino cids were present to ensuring enough nitrogen ws vilble for their synthesis. In experiments 1 nd 2, diet smples were tken from six feeders per dietry tretment 3 d fter the beginning of the tril nd 3 d prior to the end of the tril nd stored t 20 C, then CP (method ; AOAC Int., 2012) nd totl AA nlyses were conducted in duplicte on composite smples (Ajinomoto Hertlnd Inc., Chicgo, IL). Dietry smples were lso nlyzed for DM (method

3 Vline dose response in growing pigs 593 Tble 1. Diet composition on n s-fed bsis SID Vl:Lys Item Experiment 1: 75.5% b Experiment 2: 78.0% b Ingredient Corn Soyben mel (46% CP) Dried distillers grins with solubles Corn Oil 0.50 Choice white grese 0.50 Limestone Monoclcium phosphte (21.5% P) 0.30 Diclcium phosphte (18.5% P) 0.45 Slt Trce minerl premix c Vitmin premix d Vitmin-minerl premix e Phytse f L-Lys HCl DL-Met L-Thr L-Trp L-Vl L-Ile TOTAL Clculted nlysis Stndrdized ilel digestible (SID) AA, % Lys Ile:Lys Leu:Lys Met:Lys Met & Cys:Lys Thr:Lys Trp:Lys Vl:Lys ME, kcl/kg 3,358 3,355 NE NRC, kcl/kg 2,555 2,560 SID Lysine:NE, g/mcl CP, % C, % Stnd. Totl Trct Dig. (STTD) P, % C:P C:P (STTD P) Diets were fed from 31.3 to 44.9 kg BW in experiment 1 nd 25.4 to 40.7 kg BW in experiment 2. Corn, dried distillers grins with solubles (DDGS), nd soyben mel prior to ech experiment were nlyzed for CP nd totl mino cid concentrtions nd NRC (2012) SID digestibility vlues were used in the diet formultion. b The lowest diet within the experiment ws the the sme s the listed high diet with the exception of the lck of L-Vl ddition which resulted in Vl:Lys of 62.5% for experiment 1 nd 60.6% for experiment 2. Within ech experiment the low nd high diet were blended in the pproprite proportions to result in intermedite dietry tretments: 62.5, 65.9, 69.6, nd 73.0, SID Vl:Lys in experiment 1 nd 60.6, 63.9, 67.5, 71.1, nd 74.4 SID Vl:Lys in experiment 2. c Provided per kg of premix: 33 g Mn from mngnese oxide, 110 g Fe from iron sulfte, 110 g Zn from zinc oxide, 16.5 g Cu from copper sulfte, 0.33 g I from ethylenedimine dihydriodide, nd 0.30 g Se from sodium selenite. d Provided per kg of premix: 7,054,720 IU vitmin A; 1,102,300 IU vitmin D3; 35,274 IU vitmin E; 3,527 mg vitmin K; mg riboflvin; 22,046 mg pntothenic cid; 39,683 mg nicin; nd 26.5 mg vitmin B12. e Provided per kg of premix: 3.3 g Mn from mngnese oxide, 30.9 g Fe from iron sulfte, 30.9 g Zn from zinc oxide, 3.1 g Cu from copper sulfte, 0.16 g I from ethylenedimine dihydriodide, nd 0.12 g Se from sodium selenite, 2,910,072 IU vitmin A; 440,920 IU vitmin D3; 8,047 IU vitmin E; 1,047 mg vitmin K; 1,984 mg riboflvin; 6,854 mg pntothenic cid; 14,991 mg nicin; nd 7.94 mg vitmin B12. f Provided 500 phytse units (OptiPhos, Huvephrm, Pechtree, GA) per kg of diet in experiment 1 nd provided 330 phytse units (Axtr PHY, DuPont, Wilmington, DE) per kg of diet in experiment 2.

4 594 Gonçlves et l. Tble 2. Diet chemicl (clculted) nlysis on n s-fed-bsis Experiment 1: stndrdized ilel digestible Vl:Lys rtio, % Item DM 86.8 (87.0) 86.9 (87.0) 87.2 (87.0) 86.9 (87.0) 87.0 (87.0) 87.2 (87.0) CP 14.6 (13.9) 14.2 (13.9) 14.4 (13.9) 14.2 (14.0) 14.3 (14.0) 14.5 (14.0) Lys 0.97 (0.97) 0.98 (0.97) 1.03 (0.97) 0.94 (0.97) 0.94 (0.97) 0.96 (0.97) Ile 0.55 (0.53) 0.53 (0.53) 0.57 (0.53) 0.52 (0.53) 0.52 (0.53) 0.54 (0.53) Leu 1.38 (1.34) 1.38 (1.34) 1.44 (1.34) 1.32 (1.34) 1.34 (1.34) 1.40 (1.34) Met 0.33 (0.36) 0.33 (0.36) 0.34 (0.36) 0.32 (0.36) 0.31 (0.36) 0.32 (0.36) Met & Cys 0.60 (0.60) 0.59 (0.60) 0.62 (0.60) 0.56 (0.60) 0.56 (0.60) 0.57 (0.60) Thr 0.65 (0.66) 0.67 (0.66) 0.68 (0.66) 0.63 (0.66) 0.63 (0.66) 0.64 (0.66) Trp 0.18 (0.20) 0.18 (0.20) 0.18 (0.20) 0.18 (0.20) 0.18 (0.20) 0.19 (0.20) Vl 0.65 (0.59) 0.64 (0.62) 0.69 (0.65) 0.66 (0.68) 0.69 (0.71) 0.73 (0.73) Experiment 2: stndrdized ilel digestible Vl:Lys rtio, % Item DM 87.9 (86.7) 87.8 (86.7) 86.9 (86.7) 87.0 (86.7) 87.4 (86.7) 87.6 (86.7) 87.5 (86.7) CP 13.8 (13.6) 13.8 (13.7) 14.5 (13.7) 13.8 (13.7) 13.8 (13.7) 13.9 (13.7) 13.9 (13.7) Lys 0.97 (0.96) 0.95 (0.96) 0.98 (0.96) 1.01 (0.96) 1.05 (0.96) 1.03 (0.96) 0.98 (0.96) Ile 0.54 (0.52) 0.54 (0.52) 0.57 (0.52) 0.54 (0.52) 0.55 (0.52) 0.55 (0.52) 0.55 (0.52) Leu 1.34 (1.31) 1.37 (1.31) 1.38 (1.31) 1.34 (1.31) 1.30 (1.31) 1.35 (1.31) 1.33 (1.31) Met 0.32 (0.35) 0.30 (0.35) 0.33 (0.35) 0.32 (0.35) 0.33 (0.35) 0.32 (0.35) 0.33 (0.35) Met & Cys 0.57 (0.59) 0.55 (0.59) 0.57 (0.59) 0.56 (0.59) 0.57 (0.59) 0.58 (0.59) 0.57 (0.59) Thr 0.69 (0.66) 0.64 (0.66) 0.67 (0.66) 0.63 (0.66) 0.66 (0.66) 0.67 (0.66) 0.69 (0.66) Trp 0.17 (0.19) 0.17 (0.19) 0.17 (0.19) 0.17 (0.19) 0.17 (0.19) 0.17 (0.19) 0.17 (0.19) Vl 0.63 (0.56) 0.64 (0.59) 0.68 (0.62) 0.66 (0.65) 0.72 (0.68) 0.73 (0.71) 0.75 (0.74) Diet smples were tken from six feeders per dietry tretment 3 d fter the beginning of the tril nd 3 d prior to the end of the tril nd stored t 20 C, then CP nd mino cid nlysis ws conducted on composite smples by Ajinomoto Hertlnd, Inc. (Chicgo, IL). Vlues in prentheses indicte those clculted from diet formultion. Ingredient vlues for CP nd SID coefficiets from NRC (2012) long with nlyzed totl mino cid content from corn, soyben mel, nd distillers dried grins with solubles were used to derive the clculted vlues ; AOAC Int., 2012), crude fiber (method ; AOAC Int., 2012 for preprtion nd Ankom 2000 Fiber Anlyzer [Ankom Technology, Firport, NY]), sh (method ; AOAC Int., 2012), ether extrct (method ; AOAC Int., 2012 for preprtion nd ANKOM XT20 Ft Anlyzer [Ankom Technology, Firport, NY], Wrd Lbortories, Inc. Kerney, NE). Dt Collection Pens of pigs were weighed nd feed disppernce mesured t the beginning nd t the end of ech experiment to determine ADG, ADFI, nd G:F. The totl g of SID Vl intke bsed on formulted vlues were divided by totl BW gin to clculte the g of SID Vl intke per kg of gin. Sttisticl Anlysis First, responses mesured t the pen level were nlyzed seprtely for ech experiment using generl liner mixed model, tht included the fixed effect of SID Vl:Lys s ctegoricl tretment nd BW block s rndom effect using procedures outlined by Gonçlves et l., Briefly, restricted mximum likelihood (REML) ws used for estimtion of vrince components nd degrees of freedom were estimted using the Kenwrd-Roger s method (Kenwrd nd Roger, 1997). Orthogonl polynomil contrsts with coefficients djusted for uneqully spced tretments were used to conduct preliminry evlution of the functionl form of the reltionship of ADG, ADFI, G:F, BW, g of SID Vl intke per d, nd g of SID Vl intke per kg of gin. Model ssumptions were checked for ech response nd heterogeneous residul vrinces were fitted s needed. Results from the bse model nlyses were then used to inform dose response modeling for ADG nd G:F. Dt from the two experiments were combined nd fitted using single generl liner mixed model tht included the fixed effect of tretment nd the rndom effects of experiment nd BW block nested within experiment. No evidence for n experiment by tretment response ws detected so the interction term ws removed from the model. Specifiction of heterogeneous residul vrinces were fitted where pproprite using procedures outlined by Gonçlves et l. (2016).

5 Vline dose response in growing pigs 595 Tble 3. Effects of stndrdized ilel digestible (SID) Vl:Lys rtio on the growth performnce of finishing pigs from 30 to 45 kg, experiment 1 SID Vl:Lys rtio, % Probbility, P < Item Liner Qudrtic d 0 to 19 ADG, g SEM ADFI, g SEM G:F SEM BW, kg d SEM d SEM SID Vl intke, g/d SEM SID Vl, g/kg gin SEM A totl of 1,134 gilts (PIC ), initilly 31.2 ± 2.0 kg BW (men ± SD) were used in 19-d growth tril with 27 pigs per pen nd seven pens per tretment. Results from the bse nlyses were then used to develop the liner nd nonliner regression mixed models using the pproch outlined by Gonçlves et l. (2016) nd Robbins (2006)to estimte SID Vl:Lys dose responses for ADG nd G:F. Briefly, competing models included broken-line liner scending (BLL) model, broken-line qudrtic scending (BLQ) model, nd qudrtic polynomil (QP). For ADG nd G:F the competing models were specified with dosge of SID Vl:Lys s continuous vrible nd BW block within experiment s rndom effect. Additionlly, the dose response models ws expnded to ccommodte heterogeneous residul vrinces. Competing sttisticl models were compred using mximum-likelihood-bsed fit criteri nd the Byesin informtion criteri (BIC; Milliken nd Johnson, 2009). The best fitting model (lowest BIC) ws then chosen for ech response criteri. The initil nlysis within experiment dt s performed using the GLIMMIX procedure of SAS (V 9.4, SAS Institute Inc., Cry, NC). For the dose response the QP models were fit using the GLIMMIX procedure nd the broken-line regression models were fitted using the NLMIXED procedures of SAS. Results were considered significnt t P 0.05 nd mrginlly significnt t 0.05 > P RESULTS AND DISCUSSION The nlyzed diet CP nd totl AA concentrtions (Tble 2) were considered consistent with formulted vlues bsed on nlytic vribility reported by AFFCO (2015). In experiment 1, ADG incresed linerly (P = 0.009) with incresing SID Vl:Lys (Tble 3). A mrginlly significnt increse ws pprent for ADFI (liner, P = 0.098) nd finl BW (liner, P = 0.064) with incresing SID Vl:Lys fed. Both g of SID Vl intke per d nd g of SID Vl per kg of gin incresed linerly (P < 0.001) with incresing SID Vl:Lys. In experiment 2, ADG nd ADFI incresed in qudrtic mnner (P < 0.002) with incresing SID Vl:Lys wheres G:F incresed linerly (P < 0.001; Tble 4). Finl BW incresed (qudrtic, P = 0.010), g of SID Vl intke incresed per d (qudrtic, P = 0.005) nd g of SID Vl per kg of gin (liner, P < 0.001) incresed with incresing Vl:Lys. Stterplots of the observed dt nd predicted dose responses for ADG nd G:F combined for experiments 1 nd 2 s function of SID Vl:Lys rtio in 25- to 45-kg pigs re presented in Figures 1 nd 2. The best-fitting model for ADG pigs ws QP (BIC: ). In comprison the BLL model resulted in BIC of nd the BLQ model resulted in BIC of The corresponding estimted regression eqution for the QP model ws: Predicted ADG, kg = (SID Vl:Lys) (SID Vl:Lys) (Initil BW, kg) Note, the SID Vl:Lys rtio explntory vrible is expressed s proportion (i.e., 0.700). The mximum ADG ws estimted t 73.0% (95% CI:

6 596 Gonçlves et l. Tble 4. Effects of stndrdized ilel digestible (SID) Vl:Lys rtio on the growth performnce of finishing pigs from 25 to 40 kg, experiment 2 SID Vl:Lys rtio, % Probbility, P < Item Liner Qudrtic d 0 to 22 ADG, g SEM ADFI, g SEM G:F SEM BW, kg d SEM d SEM SID Vl intke, g/d SEM SID Vl, g/kg gin SEM A totl of 2,100 gilts (PIC ), initilly 25.4 ± 1.9 kg BW (men ± SD) were used in 22-d growth tril with 25 pigs per pen nd 12 pens per tretment. Figure 1. Predicted ADG nd corresponding fitted QP regression eqution s function of incresing SID Vl:Lys rtio in 25- to 45-kg pigs. The mximum men ADG ws estimted t 73.0% (95% CI: [69.5, >78.0%]) SID Vl:Lys rtio. Ech point represents the predicted ADG for typicl pen of pigs fter djusting for rndom effects. [69.5, >78.0%]) SID Vl:Lys. Note the estimte of the upper limit of the confidence intervl estimte ws outside the rnge of diet SID Vl:Lys dose tested. Thus, due to the uncertintiy pst the dose rnge the upper confidence limit ws reported s greter thn the highest dosge. The overll best-fitting model for G:F ws QP (BIC: ) compred with the BLL nd BLQ models (BIC: nd , respectively). The estimted regression eqution for the QP model ws: Predicted G:F = (SID Vl:Lys rtio) (SID Vl:Lys rtio) 2 Bsed on the best-fitting QP model, the mximum men G:F ws estimted t 69.0% (95% CI: [64.0, >78.0]) SID Vl:Lys. For the ADG nd G:F models the reltively wide rnge in the confidence intervls suggest tht

7 Vline dose response in growing pigs 597 Figure 2. Predicted G:F nd corresponding fitted QP regression eqution s function of incresing SID Vl:Lys rtio in 25- to 45-kg pigs. The mximum men G:F ws estimted t 69.0% (95% CI: [64.0, >78.0]) SID Vl:Lys rtio. Ech point represents the predicted G:F vlue fter djustment for rndom effects. the increses in ADG or G:F re reltively smll over wide rnge of dietry SID Vl:Lys. Becuse of the modest responses, the wide rnge in optimum or brekpoint dosges my ctully be in greement. Our results re consistent to the results by Bre et l. (2009), where the uthors observed tht, for 12 to 25 kg pigs, the SID Vl:Lys for optiml ADG my be greter thn those for G:F. In fct, in tht study, the SID Vl:Lys requirement for ADG ws 70% in the BLL model nd 75% in the BLQ wheres for G:F the requirements were 68% in the BLL nd 72% in the BLQ. Noteworthy, different sttisticl models cn yield different requirement estimtes (Bre et l., 2009; Gines et l., 2011) tht likely depend on the model ssumptions. This is not trivil s difference between estimtes of lterntive models cn be substntil (s high s 6 percentge points in the study by Gines et l., 2011), both from prcticl nd economic stndpoint. Crefully choosing the model tht fits the dt for estimtion nd inference is importnt. In previous studies, it is not lwys cler how well the ctul dt were fitted by ech of lterntive models, nd thus, how relevnt their estimtes for optimums might be. The reltive fit of sttisticl models cn be more objectively ssessed nd compred using fit sttistics such s the Byesin Informtion Criterion (Milliken nd Johnson, 2009), s used in this study. The NRC (2012) estimted the SID Vl:Lys requirement of 25- to 45-kg pigs t 65%. Bsed on our results, the NRC (2012) recommendtion ppers to be dequte to mximize G:F, s the estimte 65% ws within the 95% CI for SID Vl:Lys observed in our study (95% CI: [64.0, >78.0]). The NRC nd little previous literture provide confidence intervl round estimted requirements so it is difficult to determine if different estimtes re significntly different. We believe differences in sttisticl pproches contribute s source of vribility in the scientific literture In contrst, the NRC recommendtion is below our estimte for the requirement to mximize verge ADG (95% CI: [69.5, >78.0%]). This grees with other studies tht hve shown tht the SID Vl:Lys requirement of nursery nd finishing pigs rnges from 67% to 70% (Wguespck et l. 2012; Liu et l. 2015; Soumeh et l., 2015) for mximum ADG. Estimted men lowest-level SID Vl:Lys for selected trget performnce levels of ADG nd G:F bsed on corresponding best fitting models re listed in Tble 5. Note tht 99% of the mximum performnce of ADG nd G:F cn be chieved with SID Vl:Lys of pproximtely 68% nd 63.2%, respectively. A recent met-nlysis conducted by vn Milgen et l. (2013) which evluted 28 dose-response experiments in young pigs indicted SID Vl:Lys requirement of 69%, similr to our findings. In conclusion, the results herein indicte tht the SID Vl:Lys requirement rnged from 73% for mximum ADG to 69% SID for G:F in 25- to 45-kg BW pigs. However becuse of the slope of the response curve in ADG, 68% SID Vl:Lys ws ble to yield more thn 99% of mximum

8 598 Gonçlves et l. Tble 5. Estimted men lowest stndrdized ilel digestible (SID) Vl:Lys rtio for selected trget men performnce levels of growing pigs Percent of mximum performnce, % Item 95% 96% 97% 98% 99% 100% ADG G:F b < QP eqution for predicted ADG, kg = (SID Vl:Lys) (SID Vl:Lys) (Initil BW, kg), estimted to 35 kg pigs. b QP eqution for predicted G:F = (SID Vl:Lys rtio) (SID Vl:Lys rtio) 2. men ADG. Swine nutritionists my consider the mino cid rtio used in ctul diet formultion to optimize performnce nd economic return is likely to vry with vilbility nd prices of the dietry ingredients, s well s with mrket conditions for hogs (De L Llt et l., 2001). Using the estimted growth performnce equtions provided nd the reltive dose-response to incresing Vl:Lys id in n nlysis to determine the most economicl AA rtio for given sitution. ACKNOWLEDGMENTS Contribution no J from the Knss Agric. Exp. Stn., Mnhttn, KS Apprecition is expressed to New Horizon Frms (Pipestone, MN) nd Holden Frms (Northfield, MN) for providing the nimls nd reserch fcilities, nd to M. Brown, C. Steck, M. Heintz, M. Allerson, nd J. Teby for technicl ssistnce. Apprecition is lso expressed to Ajinomoto Hertlnd Inc. (Chicgo, IL) for prtil funding of the studies. LITERATURE CITED AFFCO AFFCO officil publiction. Oxford (IN): Assoc. Am. Feed Control Off. AOAC Interntionl Officil Methods of Anlysis of AOAC Int. 19th ed. Githersburg (MD): AOAC Int. Bre, R., L. Brossrd, N. Le Floc h, Y. Primot, D. Melchior, nd J. Vn Milgen The stndrdized ilel digestible vline-to-lysine requirement rtio is t lest seventy percent in postwened piglets. J. Anim. Sci. 87: doi: /js De L Llt, M., S. S. Dritz, M. R. Lngemeier, M. D. Tokch, R. D. Goodbnd, nd J. L. Nelssen Economics of incresing lysine: clorie rtio nd dding dietry ft for growing-finishing pigs rered in commercil environment. J. Swine Helth Prod. 9: org/shp/issues/v9n5/v9n5p215.html. Figuero, J. L., A. J. Lewis, P. S. Miller, R. L. Fischer, nd R. M. Diedrichsen Growth, crcss trits, nd plsm mino cid concentrtions of gilts fed low-protein diets supplemented with mino cids including histidine, isoleucine, nd vline. J. Anim. Sci. 81: doi: / x Gines, A. M., D. C. Kendll, G. L. Allee, J. L. Usry, nd B. J. Kerr Estimtion of the stndrdized ilel digestible vline-to-lysine rtio in 13-to 32-kilogrm pigs. J. Anim. Sci. 89: doi: /js Gonçlves, M. A. D., N. M. Bello, S. S. Dritz, M. D. Tokch, J. M. DeRouchey, J. C. Woodworth, nd R. D. Goodbnd An updte on modeling dose-response reltionships: ccounting for correlted dt structures nd heterogeneous vrince in liner nd non-liner mixed models. J. Anim. Sci. 94: doi: / msss Gonçlves, M. A. D., S. Nitiknchn, M. D. Tokch, S. S. Dritz, N. M. Bello, R. D. Goodbnd, K. J. Touchette, J. L. Usry, J. M. DeRouchey, nd J. C. Woodworth Effects of stndrdized ilel digestible tryptophn: lysine rtio on growth performnce of nursery pigs. J. Anim. Sci. 93: doi: /js Kenwrd, M. G., nd Roger, J. H Smll smple inference for fixed effects from restricted mximum likelihood. Biometrics. 53: doi: / Lewis, A. J., nd N. Nishimur Vline requirement of the finishing pig. J. Anim. Sci. 73: doi: / x Liu, X. T., W. F. M, X. F. Zeng, C. Y. Xie, P. A. Thcker, J. K. Htoo, nd S. Y. Qio Estimtion of the stndrdized ilel digestible vline to lysine rtio required for 25- to 120-kilogrm pigs fed low crude protein diets supplemented with crystlline mino cids. J. Anim. Sci. 93: doi: /js Milliken, G. A., nd D. E. Johnson Anlysis of messy dt: designed experiments. Vol. 1, 2nd ed., Boc Rton (FL): CRC Press. NRC Nutrient requirements of swine. 11th revised edition. Wshington (DC): Ntl. Acd. Press. doi: / Robbins, K. R., A. M. Sxton, nd L. L. Southern Estimtion of nutrient requirements using broken-line regression nlysis. J. Anim. Sci. 84:E155 E165. doi: / _supple155x Soumeh, E. A., J. vn Milgen, N. M. Sloth, E. Corrent, H. D. Poulsen, nd J. V. Nørgrd Requirement of stndrdized ilel digestible vline to lysine rtio for 8-to 14-kg pigs. Animl. 9: doi: / S Stein, H. H., M. F. Fuller, P. J. Moughn, B. Sève, R. Mosenthin, A. J. M. Jnsmn, J. A. Fernández, nd C. F. M. de Lnge Definition of pprent, true, nd stndrdized ilel digestibility of mino cids in pigs. Livest. Sci. 109: doi: /j.livsci

9 Vline dose response in growing pigs 599 Vn Milgen, J., M. Gloguen, N. Le Floc h, L. Brossrd, Y. Primot, nd E. Corrent Met-nlysis of the response of growing pigs to vline content of the diet. In: Oltjen J., E. Kebreb, nd H. Lpierre, editors. Energy nd protein metbolism nd nutrition in sustinble niml production. Wgeningen (Netherlnds): Wgeningen Acdemic Publishers, p doi: / Wguespck, A. M., T. D. Bidner, R. L. Pyne, nd L. L. Southern Vline nd isoleucine requirement of 20-to 45-kilogrm pigs. J. Anim. Sci. 90: doi: /js