Effect of Dietary Crude Protein, Lysine Level and Amino Acid Balance on Performance of Broilers 0 to 18 Days of Age

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1 Interntionl Journl of Poultry Siene 9 (): 2-27, 200 ISSN Asin Network for Sientifi Informtion, 200 Effet of Dietry Crude Protein, Lysine Level nd Amino Aid Blne on Performne of Broilers 0 to 8 Dys of Age A. Adel-Mksoud, F. Yn, S. Cerrte, C. Coto, Z. Wng nd P.W. Wldroup Deprtment of Poultry Siene, University of Arknss, Fyetteville, AR 7270, USA Astrt: The present study ws onduted to investigte the effets of dietry Crude Protein (CP), lysine nd mino id lne in mle roiler diets on performne (weight gin nd feed onversion, feed effiieny, protein effiieny rtio). Five test diet series were used: ) the 23% CP diet; 2) the 2% CP diet; 3) the 2% CP diet plus dditionl mino ids (2.68% totl CP) to provide t lest s muh of the essentil mino ids s present in the 23% CP diet; 4) the 9% CP diet nd 5) the 9% CP diet plus dditionl mino ids (20.3% totl CP) to provide t lest s muh of the essentil mino ids s present in the 23% CP diet. For eh of the five test diets series, dditionl Lys ws dded to provide totl Lys levels of.0,,,,, nd %. This resulted in totl of 35 finl experimentl tretments in 5 x 7 ftoril rrngement. Eh tretment ws fed to 6 replite pens of 6 mle roilers in eletrilly heted ttery rooders from -8 dys of ge. Birds fed the low-protein diets (2%) supplemented with EAAs (2.68% totl CP) showed signifintly the highest BW nd est FCR nd FE. There were no signifint differenes in BW etween irds fed ontrol diet (23%) nd 9% CP or 9% plus EAAs (20.3% totl CP) nd 2% CP. FC nd PER were signifintly ffeted y dietry protein levels. FCR nd FE were signifintly improved nd BW inresed signifintly y inresing dietry lysine levels up to %. An intertions of CP with or without EAAs with dietry lysine level were signifint for BW. FCR, FE, FC nd PER not signifintly influened y intertion. Thus, our results suggest tht mximum ody weight ould e otined with 2% low-cp plus EAA supplementtion whih ws the sme s tht of the hiks fed high protein diet (23% CP). Optimum dietry lysine level for performne ws ffeted y dietry protein level nd mino id lne. Key words: Crude protein, lysine, mino id lne, performne INTRODUCTION One of the importnt funtions of nutritionists is to redue the ost of feed while ensuring effiieny of utiliztion of supplemented low-protein diets with syntheti Amino Aids (AAs) to meet or exeed minimum mino id stndrds suggested y NRC (994). There is still ontroversy out this sujet in the literture. Mny studies hve reported tht young hiks fed lowprotein diet supplemented with AAs produed equl performne to hiks fed positive ontrol diets with 23% CP (Bornstein nd Lipstein, 975; Shutte, 987; Prr nd Summers, 99; Hn et l., 992; Morn et l., 992; Deshepper nd de Groote, 995). In ddition, Cifti nd Ceyln (2004) reported tht hiks fed sl diet ontining high CP (2%) showed poorer performne thn those fed low CP (9.3 nd 7.97%) plus AAs during strter period. It is ommonly greed tht greter performne in hiks n e hieved if the Essentil Amino Aids (EAA) in low CP diets were equivlent to those needed in the higher CP diets nd when lne of AAs is mintined (Pinhsov et l., 990; Cifti nd Ceyln, 2004). On the other hnd, other studies (Prsons nd Bker, 982; Bregendhl et l., 2002; Si et l., 2004; Jing et l., 2005; Wldroup et l., 2005) hve reported impired weight gin nd feed effiieny when roilers were fed low protein mino id-supplemented diets. The resons for the impired performne otined from the ove studies with regrds to low protein supplemented mino id diets remins unknown. Dietry lysine is usully the seond limiting Amino Aid (AA) ehind methionine for poultry fed orn-soyen mel diets nd prtiulrly importnt in improving performne, espeilly with regrd to rest met yield (Morn nd Bilgili, 990; Kidd et l., 998; Kerr et l., 999; Broz et l., 2000; Ldn et l., 200; Urdnet-Rinon nd Leeson 2004; Cfé nd Wldroup, 2006). Moreover, Lys ws used in the development of idel mino id rtios to express ll other essentil AA s perentge of Lys, under the idel protein onept (Bker nd Hn, 994; Emmert nd Bker, 997; Bker et l., 2002). The reltionship etween dietry protein level nd lysine requirements in ommeril roiler diets were noted y Almquist (952) who stted tht the level of n essentil mino id required for optimum hik performne ws positive liner funtion of the dietry CP level. The mino id requirements (% of CP) for mximum growth proly derese with inresing dietry CP (Aee nd Morris, 990,; Morris et l., 999). However, Hurwitz et l. (998) found n inrese in weight gin Corresponding Author: A. Adel-Mksoud, Deprtment of Animl nd Poultry Nutrition, Desert Reserh Center, Ciro, Egypt 2

2 Int. J. Poult. Si., 9 (): 2-27, 200 with inresing lysine supplementtion on the 23% protein diet. More reently, Sterling (2002) nd Sterling et l. (2003) onluded tht the mino id requirements of roilers re onstnt proportion of CP levels t lest in the rnge of CP levels ommonly fed. Thus, the ojetive of our study ws to test the effet of dietry protein, lysine nd mino id level on performne of roiler hiks fed low-protein diets to meet the minimum essentil mino ids requirements ording to NRC (994) or plus dditionl essentil mino ids identil s tht of the hiks fed high protein diet (23% CP). MATERIALS AND METHODS Three sl diets were formulted using ground yellow orn, dehulled solvent extrted soyen mel nd orn gluten mel s the intt soures of protein. Diets were formulted to ontin 9, 2, or 23% rude protein nd to meet or exeed minimum mino id stndrds suggested y NRC (994) with the stipultion tht Lys ws fixed t.0% of the diet. A dietry eletrolyte lne ((N+K)-Cl) of 250 meq/kg ws speified for ll diets nd ws otined y vrying levels of feed grde sodium hloride nd sodium ironte. The rude protein nd moisture ontent of the primry ingredients were determined prior to formulting the diets, with mino id ontent nd digestiility oeffiients suggested y mjor mino id produer (Ajinomoto Hertlnd, Chigo IL) used in the formultion. Diets were supplemented with omplete vitmin nd tre minerl mixes. Composition nd lulted nutrient ontent of the sl diets is shown in Tle. Modifitions were mde to the sl diets to rrive t totl of five test diet series. These inluded ) the 23% CP diet; 2) the 2% CP diet; 3) the 2% CP diet plus dditionl mino ids to provide t lest s muh of the essentil mino ids s present in the 23% CP diet (2-PLUS); 4) the 9% CP diet nd 5) the 9% CP diet plus dditionl mino ids to provide t lest s muh of the essentil mino ids s present in the 23% CP diet (9-PLUS). A lrge th of eh of these sl diets suffiient for mixing the finl test diets were mde nd liquots used for further supplementtion with lysine. For eh of the five test diets series, dditionl Lys ws dded in the form of L-Lysine HCl to provide totl Lys levels of.0,,,,, nd %. This resulted in totl of 35 finl experimentl tretments in 5 x 7 ftoril rrngement. Mle hiks of ommeril roiler strin (Co 500; Co-Vntress, Silom Springs AR) were otined from lol hthery where they hd een vinted in ovo for Mrek s disese nd hd reeived vintions for Newstle Disese nd Infetious Bronhitis post hth vi orse spry. Six hiks were pled in eh of 20 omprtments in eletrilly heted ttery rooders with rised wire floors. Continuous 24 h fluoresent lighting ws used. Test diets fed in msh form nd tp Tle : Composition (g/kg) nd lulted nutrient nlysis of sl diets Ingredients 9% CP 2% CP 23% CP Yellow orn Soyen mel 47.5% Corn gluten mel 60% Poultry oil Defluorinted phosphte Ground limestone Vitmin premix Feed grde slt MHA Sodium ironte Mintrex P_Se L-Lysine HCl L-Threonine Vrile Totl Crude protein % DEB meq/kg ME kl/kg Met Lys Trp Thr Ile His Vl Leu Arg TSAA Gly+Ser Phe+Tyr Sodium Dig Met Dig Lys Dig Trp Dig Thr Dig Arg Dig TSAA Provides per kg of diet: vitmin A 775 IU; holeliferol 55 IU; vitmin E 6.53 IU; vitmin B mg; rioflvin 6.6 mg; niin 39 mg; pntotheni id 0 mg; mendione.5 mg; foli id 0.9 mg; holine 000 mg; thimin.54 mg; pyridoxine 2.76 mg; d-iotin mg; ethoxyquin 25 mg. 2 Provides per kg of diet: Mn (s mngnese methionine hydroxy nlogue omplex) 40 mg; Zn (s zin methionine hydroxy nlogue omplex) 40 mg; Cu (s opper methionine hydroxy nlogue omplex) 20 mg; Se (s selenium yest) 0.3 mg. 3 Vrile levels of supplementl mino ids wter were provided for d liitum onsumption. Six replite pens, strtified ross tiers of the ttery, were ssigned to eh of the 35 dietry tretments. Men ody weights y pen were otined t nd 8 d of ge. Feed onsumption during the test period ws determined. Birds were heked twie dily for mortlity; ny ird tht died ws weighed to djust feed onversion. Dt were sujeted to nlysis of vrine s omplete ftoril rrngement with protein level, with nd without mino ids supplementtion nd lysine level s min effets nd two-wy intertions. 22

3 Int. J. Poult. Si., 9 (): 2-27, 200 Anlysis used the generl liner models proedure of SAS (SAS Institute, 99). Mortlity dt were trnsformed to squre root of n+ prior to nlysis; dt re presented s nturl numers. All sttements of proility re sed on P<0.05. RESULTS AND DISCUSSION The min effets of dietry protein level nd totl lysine level re shown in Tle 2. Birds fed the 2% CP diet supplemented with the EAAs (2.68% totl CP) t levels equl to those in the 23% CP diet showed signifintly the highest BW nd est FCR nd FE ompred to the other tretment groups. Moreover, there were no signifint differenes in BW etween irds fed ontrol diet (23%) nd 9% CP or 9% plus EAAs (20.3% totl CP) nd 2% CP. The FC nd PER were signifintly ffeted y dietry protein levels. Birds fed the high CP sl diet (23%) hd lower FC nd etter PER ompred to those fed on the low CP diet with or without EAAs supplemented, Tle 2. These results re in greement with those found y Wldroup et l. (2005) who reported tht mximum growth rte of young hikens ould e otined with 9% CP diet supplemented with rystlline EAA (2.4% totl CP) tht ws equivlent to minimum requirements. In ddition this diet improved protein utiliztion effiieny ompred with stndrd 23% protein diet. Severl workers hve onfirmed the sme results (Bornstein nd Lipstein, 975; Summers nd Leesson, 985; Shutte, 987; Stillorn nd Wldroup, 989; Prr nd Summers, 99; Hn et l.,992; Morn et l., 992; nd Desherpper nd de Groote, 995). Reently, Cifti nd Ceyln (2004) reported tht sl diet ontining high CP (2%) resulted in poorer performne thn low CP (9.3 nd 7.97%) during strter period when the low-cp sl diets were supplemented with syntheti AAs to mth AA ontent of the ontrol diet. The supplementl rystlline AA of the low CP sl diet (2%) equivlent to those in the 23% CP diet might hve resulted in etter overll AA vilility nd etter performne euse AA sored in free form re metolized in the enteroytes to lrger extent thn AA sored in peptide form (Bregendhl et l., 2002). Moreover, the rystlline AA were stted to e more ioville thn intt protein-ound AA (Izquierdo et l., 988; Hn et l., 990; Chung nd Bker, 99; Cifti nd Ceyln, 2004). Therefore, Izquierdo et l. (988) nd Chung nd Bker (992) reported tht rystlline AAs re hypothesized to e 00% true nd sored 00% into the enteroytes. These fts were onfirmed y Rért (985) nd Rért et l. (992), whih showed differenes etween the pperne of AA in the portl lood fter mels of free AA nd intt protein or peptides. Furthermore, Noy nd Skln (995) nd Trvid (995) suggested tht the reltively low mino id digestiility t 4 d for most feed ingredients my imply tht the development of rude protein nd mino id digestion is inomplete t 4 d. This ft ws onfirmed y Nitsn et l. (99) who demonstrted tht trypsin nd hymotrypsin tivities (unit/kg ody weight) in pnres inresed to mximum t d post-hthing nd ws redued t 23 d. Moreover, Noy nd Skln (2002) reported tht the effiieny of protein retention deresed s dietry protein inresed from 8, 23 nd 28% CP during the first week posthth. The present results showed tht the hiks fed 23% CP hd lower feed intke ompred to those fed low-cp diet with or without supplementl AAs. The results were lso previously onfirmed y severl studies (Prsons Tle 2: Growth performne of roiler hiks s ffeted y dietry rude protein, lysine level nd mino id lne t 0-8d of ge Prmeters Awt8 FCR FE FC PER Mort % Protein Lysine AA AA d SEM P-vlue < < d SEM P-vlue < , Mens with different supersripts in the sme olumn re signifintly different (P<0.05). Awt8 = Averge weight t 8 dy; FCR = Feed Conversion Rtio; FE = Feed Effiieny; FC = Feed Consumption; PER = Protein Effiieny Rtio;Mort = Mortlity 23

4 Int. J. Poult. Si., 9 (): 2-27, 200 nd Bker, 982; Nkht nd Anderson, 982; Pesti of ge were otined with dietry lysine levels higher nd Flether, 984; Fnher nd Jensen, 989; Aletor thn % in roiler diets 0 to 4 dy of ge irrespetive et l., 2000; Skln nd Plvnik, 2002). These studies of dietry lysine level in the rnge of.0-% from 5- reported deresed feed intke with inresed CP. In 49 dy of ge. Kidd et l. (997) reported tht inresing ddition, Fnher nd Jensen (989) suggested tht totl lysine from.-.2% improved dily weight gin speifi mino ids rther thn CP per se re nd feed effiieny of roiler hiks -8 dy of ge. In instrumentl in depressing the feed intke. Moreover, ddition, severl studies suggested tht dietry lysine the inresed feed intke ws often oserved in requirements of roilers re higher thn indited y literture in hikens fed low-cp mino id NRC (994) during the strter period for mximum supplemented diets (Aletor et l., 2000; Roserough weight gin, rest musle weight nd feed effiieny nd MMurtry, 993; Fnher nd Jensen, 989,; (Morris et l., 987; Morris nd Aee, 990; Surisdirto Roserough nd Steele, 985). These results were nd Frrell, 99). explined y Aletor et l. (2000) who demonstrted tht The intertion of CP levels nd lysine level re shown wider energy/protein rtios of low-cp diets might in Tle 3. An intertion of CP with or without EAAs with inrese onsumption of dietry energy, s roilers et dietry lysine level were signifint for BW. Inresing to meet dietry protein mino id requirements. lysine from.-% in diets inresed BW for Moreover, they reported improved energy nd protein hikens fed the low-protein 2% CP plus EAAs t levels effiieny in low-cp roiler diets ompred to the ontrol to equl those in the 23% CP diet. Moreover, hiks diet. given % lysine on the low CP 2% plus EAAs diet In ontrst, other studies (Prsons nd Bker, 982; hd highest BW ompred to other tretment groups. Bregendhl et l., 2002; Si et l., 2004; Jing et l., 2005; The BW inresed with up to % lysine on the low CP Wldroup et l., 2005) reported impired weight gin 9% or 9% plus EAAs diets. The BW inresed up to nd feed effiieny when roilers were fed low protein nd % lysine for hiks fed on high 23% CP mino id-supplemented diets. This ws explined y diet. However, hiks given. nd % lysine on the Aft et l. (2006) who suggested tht supplemented high CP 23% diet hd lower BW thn other tretment free mino ids to low-cp might use sudden influx groups. The FCR, FE, FC nd PER showed no of AAs tht inrese the tolism of AAs from musles signifint intertions etween CP levels nd lysine or those sored from diet in order to mintin levels. Mortlity rte ws not signifint mong hiks homeostsis of plsm AAs profile. Further, they reeiving ll experimentl diets. resoned impirment of performne of hiks fed low- Results of the present study indite tht optimum lysine CP diets with supplemented AAs might e onsequent level ws not onstnt proportion of CP levels with or to inresed tolism of AAs. without AAs supplementtion. These results were BW inresed signifintly s dietry lysine levels onfirmed y Aee nd Morris, 990; Surisdirto nd inresed (Tle 2). Moreover, the highest BW ws Frrell, 99; Morris et l., 992; Morris et l., 999, who otined for hikens fed diets ontining % totl reported tht mino id requirements (% of CP) for dietry lysine. In the sme trend, inresed lysine mximum growth derese with inresing dietry CP supplementtion in sl diet showed the est level. Moreover, Hurwitz et l. (998) found inreses in signifint (p<0.0) vlues of FCR nd FE. However, weight gin with inresing lysine supplementtion on.% nd lysine level in hikens diets showed the the 23% protein diet. In ddition, Sterling et l. (2006) lower nd est vlues FC nd PER, respetively reported signifint intertion etween dietry protein ompred to other dietry lysine levels. Our results level nd lysine for ody weight nd feed effiieny showed tht the optimum dietry lysine levels re in the during the strter period, with Co roilers showing the rnge of.2-% for BW, FCR nd FE for roilers up to est performne t the highest lysine level t 23% CP. 8 dy of ge nd indited tht the optimum of dietry The results of this study showed the est signifint BW lysine level is higher thn.0% s suggested y NRC vlue relted to inresed lysine level up to % for (994) during strter period 0-3 week of ge. hiks fed low-cp (2% nd 9%) plus AAs These results re similr to those otined y Ldn supplementtion nd (2% nd 9% CP) without dded et l. (200) who reported tht lysine requirements for AAs. These results might e onsequene of mximum weight gin, rest musle weight nd feed improvement in iovilility of free EAAs lne tht effiieny were.28,.32 nd.2% lysine, respetively resulted in deresed optimum lysine level for roiler for 0-2 week old roilers. Dietry lysine levels of.7% growth ompred to the intt protein in the ontrol diet. for mximl weight gin nd.4% for mximl feed This ft ws onfirmed y Hurwitz et l. (998) who effiieny were estimted for roiler hiks fed diet suggested tht dding single mino ids to low CP diet ontining 23% CP to 3 week of ge (Hn nd Bker, ws more effetive in improving mino id lne 99). Moreover, Holsheimer nd Ruesink (993) thn dding high protein diets, resulting in derese demonstrted tht higher rest musle yields t 49 dy in the requirements of lysine nd rginine. 24

5 Int. J. Poult. Si., 9 (): 2-27, 200 Tle 3: Growth performne of roiler hiks s ffeted y intertion etween dietry rude Protein, lysine nd mino id lne t 8 d of ge Prmeters Awt8 FCR FE FC PER Mort % Protein % Lysine % 9.0 efghi defgh defgh defgh defgh fghi hijk AA.0 ghij defgh defghi de defgh def defghi ijkl efghi defg def defgh def defgh AA.0 jkl defgh de d l kl defgh defgh de defgh defgh SEM P-vlue , Mens with different supersripts in the sme olumn re signifintly different (P<0.05). Awt8 = verge weight t 8 dy; FCR = feed onversion rtio; FE = feed effiieny; FC = feed onsumption; PER = protein effiieny rtio; Mort = mortlity Thus, our results suggest tht mximum ody weight ould e otined with 2% low-cp plus EAAs supplementtion to the sme identil level s tht of the hiks fed high protein diet (23% CP). Chikens fed low-cp diet (9 or 2%) whih met the minimum essentil mino ids requirements ording to NRC (994) ut without dditionl EAA hd similr growth rte s did hiks fed the 23% CP positive ontrol diet. Optimum dietry lysine level for performne ws ffeted y dietry protein level nd mino id lne. Optimum dietry lysine level for roilers re higher thn suggested y NRC (994) during the strter period for mximum weight gin. REFERENCES Aee, S. nd T.R. Morris, 990. Note on the effets of protein onentrtion on responses to dietry lysine y hiks. Br. Poult. Si., 3: Aee, S. nd T.R. Morris, 990. Effets of protein onentrtion on responses to dietry tryptophn y hiks. Br. Poult. Si., 3: Aft, U., M. Ashrf nd Z. Jing, Low protein diets for roilers. World s Poult. Si. J., 62: Aletor, V.A., I.I. Hmid, E. Niess nd E. Pfeffer, Low-protein mino id-supplemented diets in roiler hikens: Effets on performne, rss hrteristis, whole-ody omposition nd effiienies of nutrient utiliztion. J. Si. Food Agri., 80: Almquist, H.J., 952. Amino id requirements of hikens nd turkeys- review. Poult. Si., 3: Bker, D.H., A.B. Btl, T.M. Prr, N.R. Augspurger nd C.M. Prsons, Idel rtio (reltive to lysine) of tryptophn, threonine, isoleuine nd vline for hiks during the seond nd third weeks posthth. Poult. Si., 8:

6 Int. J. Poult. Si., 9 (): 2-27, 200 Bker, D.H. nd Y. Hn, 994. Idel mino id profile Hn, Y., F. Cstnon, C.M. Prsons nd D.H. Bker, for hiks during the first three weeks posththing. Poult. Si., 73: Broz, W.A., H.S. Rostgno, L.F.T. Alino nd P.B. Rodrigues, Lysine levels for roiler hikens from to 2 nd 5 to 40 dys of ge. Rev. Brs. Zoote., 29: Bornstein, S. nd B. Lipstein, 975. The replement of some of the soyen mel y the first limiting mino ids in prtil roiler diets.. The vlue of speil supplementtion of hiks diets with methionine nd lysine. Br. Poult. Si., 6: Bregendhl, K., J.L. Sell nd D.R. Zimmermn, Effet of low-protein diets on growth performne 990. Intestinl sorption nd iovilility of DLmethionine hydroxyl nlog ompred to DLmethionine. Poult. Si., 69: Hn, Y., H. Suzuki, C.M. Prsons nd D.H. Bker, 992. Amino id fortifition of low-protein orn nd soyen mel diet for hiks. Poult. Si., 7: Holsheimer, J.P. nd E.W. Ruesink, 993. Effet on performne, rss omposition, yield nd finnil return of dietry energy nd lysine levels in strter nd finisher diets fed to roilers. Poult. Si., 72: Hurwitz, S., D. Skln, H. Tlpz nd I. Plvnik, 998. The nd ody omposition of roiler hiks. Poult. Si., effet of dietry protein level on the lysine nd 8: rginine requirements of growing hikens. Poult. Cfé, M.B. nd P.W. Wldroup, Intertions Si., 77: etween levels of methionine nd lysine in roiler Jing, Q., P.W. Wldroup nd C.A. Fritts, Improving diets hnged t typil industry intervls. Int. J. the utiliztion of diets low in rude protein for roiler hiken.. Evlution of speil mino id Poult. Si., 5: supplementtion to diets low in rude protein. Int. J. Chung, T.K. nd D.H. Bker, 99. Apprent nd true Poult. Si., 4: digestiility of mino ids in sein nd in Kerr, B.J., M.T. Kidd, K.M. Hlpin, G.W. MWrd nd C.L. omplete mino id mixture: Comprison of pig Qurles, 999. Lysine level inreses live ilel digestiility with the eetomized okerel performne nd rest yield in mle roilers. J. ssy. J. Anim. Si. 69(Suppl. ): 38. (Astr.). Applied Poult. Res., 8: Chung, T.K. nd D.H. Bker, 992. Apprent nd true Kidd, M.T., B.J. Kerr nd N.B. Anthony, 997. Dietry mino id digestiility of rystlline mino id intertions etween lysine nd threonine in mixture nd of sein omprison of vlues roilers. Poult. Si., 76: otined with ilel-nnulted pigs nd Kidd, M.T., B.J. Kerr, K.M. Hlpin, G.W. MWrd nd C.L. eetomized okerels. J. Anim. Si., 70: 378- Qurles, 998. Lysine levels in strter nd grower finisher diets ffet roiler performne nd Cifti, I. nd N. Ceyln, Effets of dietry threonine rss trits. J. Applied Poult. Res., 7: nd rude protein on growth performne, rse Ldn, M.C. Jr., K.N. Hsu nd R.E. Austi, 200. nd met omposition of roiler hikens. Br. Poult. Lysine nd rginine requirements of roiler Si., 45: hikens t two- to three-week intervls to eight Deshepper, K. nd G. DeGroote, 995. Effet of dietry weeks of ge. Poult. Si., 80: protein, essentil nd non-essentil mino ids Izquierdo, O.A., C.M. Prsons nd D.H. Bker, 988. on the performne nd rss omposition of mle roiler hikens. Br. Poult. Si., 36: Emmert, J.L. nd D.H. Bker, 997. Use of the idel protein onept for preision formultion of mino id levels in roiler diets. J. Applied Poult. Res., 6: Fnher, B.I. nd L.S. Jensen, 989. Influene on performne of three to six-week-old roilers of Biovilility of lysine in L-lysine HCl. J. Anim. Si., 66: Morn, E.T. Jr., R.D. Bushong nd S.F. Bilgili, 992. Reduing dietry rude protein for roilers while stisfying mino id requirements y lest-ost formultion: Live performne, litter omposition, nd yield of fst-food rss uts t six weeks. Poult. Si., 7: vrying dietry protein ontents with Morn, E.T. Jr. nd S.F. Bilgili, 990. Proessing losses, supplementtion of essentil mino ids rss qulity nd met yields of roiler hikens requirements. Poult. Si., 68: Fnher, B.I. nd L.S. Jensen, 989. Mle roiler performne during the strting nd growing periods s ffeted y dietry protein, essentil mino ids nd potssium levels. Poult. Si., 68: Hn, Y. nd D.H. Bker, 99. Lysine requirement of fst nd slow growing roiler hiks. Poult. Si., 70: reeiving diets mrginlly defiient to dequte in lysine prior to mrketing. Poult. Si., 69: Morris, T.R. nd S. Aee, 990. Effets of rginine nd protein on hik s responses to dietry lysine. Br. Poult. Si., 3: Morris, T.R., K. Al-Azzwi, R.M. Gous nd G.L. Simpson, 987. Effets of protein onentrtion on responses to dietry lysine y hiks. Br. Poult. Si., 28:

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