Brzilin Journl of Poultry Science Revist Brsileir de Ciênci Avícol ISSN 1516-635X Jul - Sept 2012/ v.14 / n.3 / 159-232 Estimtes of Methionine nd Sulfur Amino Acid Requirements for Lying Hens using Different Models Author(s) Ski AA 1 Nseri Hrsini Tbtbei MM 1 Zmni P 1 Hghight M 1 1 Deprtment of Animl Science, School of Agriculture, Bu-Ali Sin University, Hmdn, Irn 2 Young Resercher Club, Kermnshh Brnch, Islmic Azd University, Kermnshh Irn Mil Adress Ali Asghr Ski, Deprtment of Animl Science, Fculty of Agriculture, Bu-Ali Sin University, Hmdn, Irn Tel: 09183139775, +988114424195 Fx: +98 811 4424012 E-mil: drliski@yhoo.com Keywords Broken-line regression, Exponentil eqution, Methionine, Second order eqution, Totl sulfur mino cids. Submitted: October/2010 Approved: My/2012 ABSTRACT This experiment ws conducted to evlute the effects of dietry methionine (Met) content on the performnce of white commercil lying hens nd to determine Met nd totl sulfur mino cids requirements (TSAA). These requirements were estimted using three sttisticl models (broken-line regression, exponentil nd second order equtions) to evlute their bilit to determine mino cid requirements. A totl of 216 lying hens (23 wks of ge) ws used in completely rndomized design (CRD) with six tretments with four replictes of nine birds ech. The bsl diet contined 15.25% crude protein, 2830.16 kcl/kg ME nd 0.24% Met. Synthetic DL-Met ws dded to the deficient (bsl) diet in 0.05% increments to mke the other five experimentl diets (0.29, 0.34, 0.39, 0.44 nd 0.49% Met). Incresing Met level from 0.24 to 0.34% significntly incresed egg production, egg weight, egg mss, egg content, nd feed intke nd decresed feed conversion rtio (p<0.05). However, further Met increses, from 0.34 to 0.49%, no longer influenced these prmeters. Out of the three models, the broken-line regression model presented better estimtes of AA requirements. Bsed on broken-line equtions, verge Met nd TSAA requirements of the lying hens were 0.31 nd 0.60% (245.50 nd 469.25 mg/hen/dy) from 22 to 36 wks of ge, respectively. INTRODUCTION The efficiency of dietry protein utiliztion depends on the mount, composition, nd digestibility of the mino cids (AA) in the diet. Lying hen requirements should be expressed on digestible mino cid bsis, rther thn on protein. Therefore, it is importnt to formulte diets ccording to ccurte vlues of mino cid requirements. Methionine (Met), lysine (Lys), nd tryptophn (Trp) re considered s the most limiting AA in prcticl lyer diets bsed on corn nd soyben mel (Hrms & Russell, 2000). The use of liner progrmming techniques hs shown tht both the protein level nd the cost of prcticl rtions re very much ffected by the requirements of specific essentil AAs, prticulrly Met nd Lys. Therefore, estimtes of these requirements must be relible (Fisher & Morris, 1970). Indeed, Lopez & Leeson (1995) reported tht since chickens cn only utilize bout 40% of the dietry protein, it seems logicl to decrese dietry protein level in the diet, which would lso minimize nitrogen excretion. However, synthetic AA need to be dded to the diet in order to meet the requirements of limiting AA due to AA dilution when dietry protein is reduced. Formulting diets bsed on the idel protein concept is one of the methods to reduce dietry protein, which, in turn, will decrese fecl nitrogen excretion, while mintining egg production prmeters (Novk et l., 2006). 209 rev_v14_03_8_nu_514.indd 209 05/11/12 16:17
Ski AA, Nseri Hrsini R, Tbtbei MM, Zmni P, Hghight M Estimtes of Methionine nd Sulfur Amino Acid Requirements for Lying Hens using Different Models Results of studies on Met nd totl sulfur mino cids (TSAA) requirements of lying hens widely vry. Morn (1969) reported 2.9 g Met/kg requirement in diet contining 3.4 g Cys nd 12.35 MJ metbolizble energy (ME)/kg, which is equivlent to n intke of 788 mg TSAA/h/d, out of which 362 mg correspond to Met. Met requirement recommended by Hrms nd Dmron (1969) ws 275 mg vilble Met/h/d during production pek. In other studies, the recommended Met requirement vried between 300 nd 320 mg/ h/d (Crlson & Guenthner, 1969; Novcek & Crlson, 1969; Jensen et l., 1974; Sell & Johnson, 1974). The NRC (1971) recommended dily intke of 280 mg Met/d, but the requirement ws incresed to 300 mg/d in 1977, nd to 350 mg/d in 1984. In the NRC revision of 1994, the requirement ws reduced to 300 mg/d. These requirements were suggested ssuming the hen needed certin mount of TSAA nd portion of his mount ws to stisfy need for pproximtely 280 mg of Cys. The recommendtion of ARC (1975) for young lying pullets producing 50 g egg mss (EM) per hen/d ws 350 mg vilble Met of totl of 470 mg vilble TSAA/h/d. Rostngo (1990) suggested tht hens with dily feed intke (FI) of 105 g required 0.311% Met nd 0.567% TSAA or 327 nd 595 mg/d of Met nd TSAA, respectively. Ahmd et l. (1997) reported tht TSAA levels rnging from 580 to 660 mg/h/d hd no effect on performnce of lying hens. A lrge number of reports hs been published on Met nd TSAA requirements nd their supplementtion. However, there is wide vrition in recommended requirement of Met nd TSAA for lying hens. Therefore, this experiment ws conducted to determine Met nd TSAA requirements for lying hens. MATERIAL AND METHODS This study ws crried out t niml reserch sttion of Bu-Ali Sin University in August, 2009, in Hmdn- Irn. All experimentl protocols were pproved by the Animl Welfre Committee of the Agriculturl School of Bu-Ali Sin University. A totl of 216 commercil lying hens were obtined from locl supplier. After 18 wks of ge, birds received incresing stimultion of up to 16 hours of light, which ws mintined until the end of the experiment. At 22 wks of ge, hens were individully weighed nd llocted in to six tretments with four replictes of nine birds ech (three hens in ech conventionl cge, mesuring 42 40 50 cm 3 ). The bsl diet ws bsed on corn, whet, nd soyben mel (Tble 1) nd contined 15.33% crude protein 210 Tble 1 Composition nd nutrients content of the bsl diet. Ingredients (%) Bsl diet 1 Corn (8.72%) 41.90 Soyben mel (44.19%) 20.00 Whet (11.35%) 25.00 Soyben oil 2.47 Diclcium phosphte 2 1.28 Oyster shell 3 8.37 Sodium chloride 4 0.37 Minerl mix 5 0.25 Vitmin mix 6 0.25 DL- Met - L-Lys-HCl 0.11 Totl 100 Anlyzed vlues 7 (%) Crude protein 15.33 Ether extrct 2.65 Crude fiber 2.79 Ash 1.25 Met 0.24 Cys 0.28 Met+Cys 0.52 Lys 0.88 Clculted vlues 8 ME (Kcl/kg) 2832.71 C (%) 3.50 NPP (%) 0.35 N (%) 0.17 1Bsed on 100 g/h per dy. 2Contined 18.7 % P nd 22 % C. 3Contined 38% C. 4Contined 39% N. 5Per kg minerl premix supplied the following: Mn, 64 g; Zn, 44 g; Fe, 100 g ; Cu, 16 g ; I, 0.64 g; Co, 0.2 g; Se, 3 g. 6Supplied per kilogrm of diet: biotin, 0.2 mg; choleclciferol, 2,200 IU; choline, 500 mg; ethoxyquin, 65 mg; folic cid, 1 mg; nicin, 60 mg; pntothenic cid, 15 mg; pyridoxine, 5 mg; riboflvin, 5 mg; thimin, 3 mg; vitmin A, 8,000 IU; vitmin B12, 0.02 mg; vitmin E, 20 IU; vitmin K, 2 mg. (CP), 2832.71 kcl ME/kg, 0.24% Met, nd 0.52% TSAA. This diet ws formulted to meet or to exceed the NRC (1994) requirements of lyers in ly for ll nutrients, except for Met nd TSAA. Synthetic DL- Met ws dded to the deficient (bsl) diet in 0.05% increments (0, 0.05, 0.10, 0.15, 0.20, 0.25) t the expense of soyben mel to meet the desired Met nd TSAA levels in the experimentl diets. Feedstuffs nd feeds were nlyzed for crude protein (CP), ether extrct (EE), sh, nd crude fiber (CF), ccording to the procedures of the Assocition of Officil Anlyticl Chemists (AOAC, 1990; Tble 1). Energy vlues were bsed on NRC recommendtion (1994). Feedstuff AA composition ws nlyzed t the Chemicl lb of Bu-Ali Sin University (Tector pprtus, Optilb 5931 Liquid Chromtogrph, C18 column) using the method described by Rvindrn et l. (1999). The AA composition of the bsl diet, except for Met nd TSAA, covered the idel mino cid profile suggested by Schutte & De Jong (1996). rev_v14_03_8_nu_514.indd 210 05/11/12 16:17
Ski AA, Nseri Hrsini R, Tbtbei MM, Zmni P, Hghight M Estimtes of Methionine nd Sulfur Amino Acid Requirements for Lying Hens using Different Models The experimentl diets were freshly prepred nd mixed t four-week intervls. Feed (in msh form) nd wter (vi nipple drinkers) were supplied d libitum throughout the experiment. The experiment ws conducted for 14 wks (22 to 36 wks of ge), but the first 2 wk were considered s depletion period (Hrms & Russell, 1996b). The hens were individully weighed t the beginning nd t the end of the experiment, nd body weight gin (BWG) ws clculted. Feed intke, egg production (EP), egg weight (EW), EM, feed conversion rtio (FCR), egg content (EC) nd shell weight (SW) were recorded on replicte bsis. ws clculted by multiplying EP by EW minus SW. The experiment ws conducted ccording to completely rndomized design (CRD). Dt were submitted to nlysis of vrince (ANOVA), using the liner model procedure of the sttisticl pckge of SAS Institute (2004). Vrince homogeneity ws determined by Brtlett s test. Duncn s multiple rnge test (1955) ws used to compre tretment mens (p<0.05). Met nd TSAA requirements of lying hens were determined submitting BW chnge, EP, EW, EM, EC, FCR nd FI dt to regression nlysis using the brokenline model (Robbins et l., 2006), exponentil model or second order equtions. The eqution of the broken-line model ws: y = L + U (X LR R), where y = performnce prmeter (e.g., body weight, feed intke, etc.), L = the ordinte of the brekpoint in the curve; R = the bsciss of the brekpoint in the curve (requirement estimte); X LR = vlue of X less thn R; nd U= slope of the line for X less thn R. In the broken-line model, dietry Met nd TSAA concentrtion ws clculted s the concentrtion required to chieve mximum performnce, ccording to the prmeter. The eqution of the exponentil model ws: y = + b (1 e c(x d) ), where y = performnce prmeter (e.g., body weight, feed intke, etc.), = intercept (performnce of the bsl diet), b = mximum response to Met or TSAA concentrtions, e = nepher vlue, c = slope, d = Met or TSAA concentrtions in the bsl diet, nd x = Met or TSAA concentrtion in the experimentl diet. In the exponentil model, the dietry Met nd TSAA concentrtions were clculted tht were required to chieve 95% of the mximum of the performnce prmeter considered. The eqution of the second order model ws: y = + bx +cx 2 where y = performnce prmeter (e.g., body weight, feed intke, etc.), nd x = Met or TSAA concentrtion in the diet. RESULTS Methionine nd TSAA requirements estimted by exponentil equtions for EM, EC, FCR nd FI were higher thn mximum dietry Met nd TSAA supplied in this experiment (0.49 nd 0.77%, respectively; Tbles 2 nd 3). Methionine nd TSAA requirements estimted by second-order equtions, irrespective of the results, were very vrible (Tbles 4 nd 5). In this respect, broken-line regression showed better bility to estimte AA requirements. On the other hnd, highest Tble 2 Exponentil equtions of Met requirements Met Mesurement Eqution Body weight chnge y = 83.91 + 98.87 (1 e -21.87(x-0.24) ) 0.62 0.377 y = 50.45 + 23.51 (1 e -0.31(x-0.24) ) 0.56 0.303 y = 48.72 + 6.14 (1 e -11.65(x-0.24) ) 0.85 0.490 Egg mss y = 26.79 187.40 (1 e -47.47(x-0.24) ) 0.24 > 0.490 y = 42.42 + 8.07 (1 e -10.62(x-0.24) ) 0.92 > 0.490 Feed conversion rtio y = 2.77 + 11.05 (1 e -0.19(x-0.24) ) 0.43 > 0.490 Feed intke y = 65/70 346.50 (1 e -0.25(x-0.24) ) 0.21 > 0.490 Coefficient of determintion. y, performnce prmeters; e, nepher vlue; x, Met or TSAA concentrtion in the diet. 211 rev_v14_03_8_nu_514.indd 211 05/11/12 16:17
Ski AA, Nseri Hrsini R, Tbtbei MM, Zmni P, Hghight M Estimtes of Methionine nd Sulfur Amino Acid Requirements for Lying Hens using Different Models Tble 3 Exponentil equtions of TSAA requirements Mesurement Eqution TSAA Body weight chnge y = 83.91 + 98.87 (1 e -21.87(x-0.24)) 0.62 0.730 y = 50.45 + 23.51 (1 e -0.31(x-0.24)) 0.56 0.618 y = 48.72 + 6.14 (1 e -11.65(x-0.24)) 0.85 0.760 Egg mss y = 26.79 187.40 (1 e -47.47(x-0.24)) 0.24 > 0.770 y = 42.42 + 8.07 (1 e -10.62(x-0.24)) 0.92 > 0.770 Feed conversion rtio y = 2.77 + 11.05 (1 e -0.19(x-0.24)) 0.43 > 0.770 Feed intke y = 65/70 346.50 (1 e -0.25(x-0.24)) 0.21 > 0.770 Coefficient of determintion. y, performnce prmeter; e, nepher vlue; x, Met or TSAA concentrtion in the diet. coefficient of determintion vlues of the evluted performnce prmeters (except for EC) mong the three sttisticl models were obtined with brokenline regression. Thus, Met nd TSAA requirements estimted by broken-line regression equtions re discussed below. Incresing dietry Met content from 0.24 to 0.29% significntly incresed BWG (p<0.05; Tble 6). However, BWG ws not significntly different when hens were fed diets contining 0.29 to 0.49% Met (0.57 to 0.77% TSAA). Broken-line regression equtions of BWG estimted Met nd TSAA requirements of 0.323 nd 0.603%, respectively (Tble 7). Bsed on FI dt nd nlysis of feedstuffs smples, these vlues re equivlent to 255 nd 475 mg/h/d, respectively. EP of hens receiving the diet with 0.24% Met (0.52% TSAA) ws significntly lower compred with hens receiving ll other diets (p<0.05, Tble 6). Met supplementtion in the bsl diet significntly (p<0.05) incresed EP when 0.34% Met (0.62% TSAA) ws fed. In contrst, incresing Met level from 0.34 to 0.49% (0.62 to 0.77% TSAA) did not improve EP. Brokenline regression of EP indicted tht Met nd TSAA requirements were 0.316 nd 0.596% (249 nd 470 mg/h/d), respectively (Tble 7). No significnt EW reduction ws detected when Met content ws reduced from 0.49 to 0.34% (0.77 to 0.62% TSAA, Tble 6). On other hnd, EW ws significntly reduced when Met levels were below 0.34% (p<0.05). Bsed on broken-line regression equtions, Met nd TSAA requirements for EW were 0.303 nd 0.620% (239 nd 489 mg/h/d), respectively (Tble 7). Egg mss significntly incresed (p<0.05) from 23.24 to 44.00 g/h/d when Met level incresed from 0.24% (0.52% TSAA) to 0.34% (0.62% TSAA) (Tble 6). Tble 4 Second-order equtions of Met requirement for performnce prmeters Mesurement Eqution Met Body weight chnge y = -404.30 + 2869.40x 3458.10x 2 0.61 0.415 y = -85.52 + 837.50x 1071.30x 2 0.51 0.391 y = 29.99 + 106.60x 116.00x 2 0.84 0.459 Egg mss y = -57.25 + 478.40x 563.30x 2 0.69 0.425 y = 18.41 + 136.10x 147.40x 2 0.92 0.462 Feed conversion rtio y = 6.44 21.31x + 24.97x 2 0.74 0.427 Feed intke y = -17.22 + 496.10x 604.80x 2 0.64 0.410 Coefficient of determintion. y, performnce prmeter; x, AA concentrtion in the diet. 212 rev_v14_03_8_nu_514.indd 212 05/11/12 16:17
Ski AA, Nseri Hrsini R, Tbtbei MM, Zmni P, Hghight M Estimtes of Methionine nd Sulfur Amino Acid Requirements for Lying Hens using Different Models Tble 5 Second-order equtions of TSAA requirement for performnce prmeters Mesurement Eqution TSAA Body weight chnge y = -1384.90 + 4529.00x 3256.00x 2 0.61 0.695 y = -404.00 + 1437.50x 1071.30x 2 0.51 0.671 y = - 8.95 + 171.60x 116.00x 2 0.84 0.740 Egg mss y = -235.40 + 793.90x 563.30x 2 0.69 0.705 y = - 184.40 + 629.00x 441.90x 2 0.58 0.712 Feed conversion rtio y = 14.36 35.29x + 24.97x 2 0.74 0.707 Feed intke y = -203.50 + 834.80x 604.80x 2 0.64 0.690 Coefficient of determintion. y, performnce prmeter; x, AA concentrtion in the diet. Differences in EM were inconsistent nd not significnt when dietry Met rnged from 0.34 to 0.49% (0.62 to 0.77% TSAA). According to the broken-line regression equtions, Met nd TSAA requirements for EM were 0.316 nd 0.595% (249 nd 469 mg/h/d), respectively (Tble 7). followed the similr trend s EM (Tble 6). A grded reduction of dietry Met content from 0.34 to 0.24% (0.62 to 0.52% TSAA) led to progressive nd significnt (p<0.05) decrese in EC (40.49 vs. 21.50 g, respectively). decresed nd then incresed, lbeit not sttisticlly, s dietry Met content incresed from 0.34 to 0.49% (0.62 to 0.77% TSAA). Broken-line regression equtions for EC showed tht Met nd TSAA requirements were 0.324 nd 0.604% (255 nd 476 mg/h/d), respectively (Tble 7). Feed conversion rtio ws not ffected by dietry Met level until it ws higher thn 0.34% (0.62% TSAA) (Tble 6). However, further reductions in dietry Met stedily incresed FCR whenever dietry Met ws reduced (p<0.05). Bsed on broken-line regression equtions, Met nd TSAA requirements were 0.309 nd 0.585% (244 nd 461 mg/h/d), respectively (Tble 7). Incresing dietry Met content from 0.24 to 0.34% significntly incresed FI (p<0.05; Tble 6). Feed Tble 6 Performnce of commercil lying hens in response to different Met nd TSAA levels Dietry Met (TSAA) (%) Initil body weight (g) Body weight chnge (g) Egg production (%) (g) Egg mss (g/h/d) (g) FCR (g feed/g egg) Feed intke (g/h/d) 0.24 (0.52) 1061.47 84.97 b 50.52 c 48.80 c 23.24 c 21.50 c 2.87 64.53 c 0.29 (0.57) 1081.94 143.22 70.40 b 51.02 b 35.96 b 31.40 b 2.22 b 78.93 b 0.34 (0.62) 1079.36 180.97 81.11 53.63 44.00 40.49 1.94 c 84.42 0.39 (0.67) 1069.78 181.31 74.95 b 53.40 40.24 b 35.60 b 2.10 bc 81.53 b 0.44 (0.72) 1088.19 179.48 68.73 b 54.18 41.89 b 35.84 b 1.97 c 80.63 b 0.49 (0.77) 1091.97 178.22 72.16 b 54.62 43.95 40.45 1.90 c 83.20 MSE 60.05 34.90 27.15 0.76 17.52 19.58 0.02 16.38 P 0.8640 0.0016 0.0006 Mens in the sme column without common superscript significntly differ (p<0.05). 213 rev_v14_03_8_nu_514.indd 213 05/11/12 16:17
Ski AA, Nseri Hrsini R, Tbtbei MM, Zmni P, Hghight M Estimtes of Methionine nd Sulfur Amino Acid Requirements for Lying Hens using Different Models Tble 7 Broken-line regression equtions of Met nd TSAA requirements for performnce prmeters Mesurement Met b TSAA Body weight chnge y = 181.8 + 1.165 (x 0.323) 0.63 y = 181.8 + 1.165 (x 0.603) 0.63 y = 80.78 + 0.397 (x 0.316) 0.64 y = 80.78 + 0.397 (x 0.596) 0.64 y = 53.95 + 0.044 (x 0.303) 0.85 y = 53.31 + 0.045 (x 0.620) 0.87 Egg mss y = 42.52 + 0.254 (x 0.316) 0.77 y = 42.21 + 0.254 (x 0.595) 0.77 y = 38.07 + 0.198 (x 0.324) 0.68 y = 38.07 + 0.198 (x 0.604) 0.68 Feed conversion rtio y = 1.98 + 0.013 (x 0.309) 0.83 y = 2.03 + 0.013 (x 0.585) 0.84 Feed intke y = 83.44 + 0.288 (x 0.306) 0.76 y = 83.44 + 0.288 (x 0.586) 0.76 Averge requirement 0.31 0.60 Determined by the procedure of Robbins et l. (2006). b Coefficient of determintion. y, performnce prmeter; X, vlue of X less thn R. intke ws not significntly different mong hens tht received diets contining 0.34 to 0.49% Met (0.62 to 0.77% TSAA). According to the broken-line regression equtions, Met nd TSAA requirements for FI were 0.306 nd 0.586% (241 nd 462 mg/h/d), respectively (Tble 7). DISCUSSION There re two min dvntges of using the brokenline method compred with the exponentil nd the second-order methods. Firstly, the broken-line method estimtes AA requirements bsed on the best response, not tking into ccount sfety mrgins or economic spects. Secondly, the broken-line method pplies to rel conditions nd objective cses, wheres the other methods re bsed on hypotheses nd subjective cses, such s economic issues. Non-liner exponentil nd second-order models use confidence intervl (in most cses 95%) with probbility of error (5 %), which reduces the ccurcy of these two models (Mck et l., 1999; Bker et l., 2002). Also, the highest coefficient of determintion of ech performnce prmeters (except for EC) ws obtined with broken-line regression. Thus, broken-line regression provided the best estimtes of AA requirements. Mny reserchers reported tht broken-line regression is the best method for estimting mino cid requirements (Mck et l., 1999; Bker et l., 2002; Bregendhl et l., 2008), which is consistent with the findings of the present experiment. In this experiment, Met supplementtion resulted in n increse in BWG. This result is in greement with the 214 reports of Hrms & Russell (1998) nd Nrváez-Solrte et l. (2005) with lying hens. However, Shfer et l. (1998) reported tht dietry Met content did not ffect verge BWG of lyers. It should be mentioned tht the minimum dietry Met level used by Shfer et l. (1998) ws 0.18% higher thn the minimum level used in our study, nd possibly, Met deficiency effects were not evluted by Shfer et l. (1998). McDevitt et l. (2000) nlyzed body mss dt using feed intke s covrite (becuse FI ws different mong tretments) in their experiment, nd observed tht chick BWG ws still highly influenced by the ddition of DL-Met to the diet. The TSAA requirement estimted by Nrváez- Solrte et l. (2005) for mximum BWG (0.683%) ws 8% higher thn the vlue obtined in the present study (0.603%). Also, the TSAA requirements estimted by Nrváez-Solrte et l. (2005) for ech production prmeter were higher those obtined here, nd the resons for these differences re discussed below. The increse in EP due to incresing dietry Met level observed in the present study hs lredy been reported in literture (Keshvrz, 2003; Hrms & Russell, 2003; Liu et l., 2005; Nrváez-Solrte et l., 2005; Wu et l., 2005; Novk et l., 2006). Hrms & Russell (2003) recommended 245.6 mg Met/h/d, which is very close to our estimte (249 mg/h/d). However, the TSAA requirements reported by Nrváez-Solrte et l. (2005) for mximum EP (0.658%) ws 6.3% higher thn our estimte (0.596%). In the present experiment, the heviest eggs were produced by hens fed diets contining more thn 0.34% Met. This observtion is consistent with the findings of Keshvrz (2003), Hrms & Russell (2003), rev_v14_03_8_nu_514.indd 214 05/11/12 16:17
Ski AA, Nseri Hrsini R, Tbtbei MM, Zmni P, Hghight M Estimtes of Methionine nd Sulfur Amino Acid Requirements for Lying Hens using Different Models Liu et l. (2005), Nrváez-Solrte et l. (2005), nd Wu et l. (2005). Met requirement for EW in our study ws 239 mg/h/d, which is 72.2 mg lower thn the vlue estimted by Hrms & Russell (2003) (311.2 mg/ h/d). Hens in the study conducted by Hrms & Russell (2003) were pproximtely 23 wks older thn those in the present study; therefore, their hens produced lrger eggs. Lyer ge my be led to differences in recommended Met requirements. On the other hnd, the TSAA requirement determined by Nrváez-Solrte et l. (2005) for EW (0.681%) ws higher thn vlues estimted in present study. Egg mss ws incresed in 22.76 g/h/d when 0.1% DL-Met ws supplemented to the bsl diet. The negtive effect of low Met diets on EM hs been lso reported by other reserchers (Liu et l., 2005; Nrváez- Solrte et l., 2005; Wu et l., 2005; Novk et l., 2006). In the current experiment, TSAA requirement for mximum EM ws 0.595%, which is 6.9% lower thn the requirement reported by Nrváez-Solrte et l. (2005). exhibited similr trend s EM, with decline s dietry Met decresed. This reduction ws expected s reduced Met levels resulted in lower EP nd EW. This observtion grees with the results reported by Crey et l. (1991) nd Hrms & Russell (1998, 2003). Met supplementtion in the bsl diet significntly decresed FCR up to the 0.34% level (0.62% TSAA). The results of mny studies hve led to the ssumption tht FCR of lying hens improves when Met is supplemented in the diets (Novk et l., 2004; Nrváez- Solrte et l., 2005; Wu et l., 2005). The explntion for the improved FCR with incresing Met nd TSAA levels my be ttributed to better AA blnce (Nrváez-Solrte et l., 2005). It is lso possible tht hens become more efficient in utilizing the vilble dietry Met. There re few studies determining Met nd TSAA requirement for FCR. Incresing dietry Met content from 0.24 to 0.34% significntly incresed FI. A similr effect of dietry Met content on lyer FI ws lso reported by Hrms & Russell (2003), Nrváez-Solrte et l. (2005) nd Novk et l. (2006). In contrst, Schutte & Pck (1995b) suggested tht TSAA hs no effect on FI. It seems tht Met nd TSAA levels my regulte lyer FI. Hrper et l. (1970), Austic (1986), nd Hurwitz et l. (1998) reported tht Met nd TSAA my modify plsm AA profile in order to stimulte ppetite. Feed intke reduction when highly deficient Met diets re fed lso reduces the intke of non-essentil AA, such s glutmic cid, cystine nd glycine, which re importnt N sources. 215 These AA my become limiting or essentil AA my be used for non-essentil purposes, which my limit protein (egg) synthesis. In the current experiment, bsed on broken-line regression equtions, the verge Met nd TSAA requirements for mximum BWG, EP, EW, EM, EC nd FI, nd minimum FCR ws 0.31 nd 0.60% from 22 to 36 wks of ge, respectively. According to the verge FI clculted in this experiment (78.87 g/h/d), these vlues re equivlent to 245.50 nd 469.25 mg/h/d, respectively. Mrtin et l. (1969) nd Novcek & Crlson (1969) reported tht lying hens required 250 mg Met nd 460 mg TSAA/h/d, which re close to the requirements estimted in the current experiment. Met nd TSAA requirements estimted by Rostngo (1990) (0.310 nd 0.567%, respectively) lso re very close to those of present study. The Met requirement determined in this study (0.31%) ws similr to the 0.30% reported by Jensen et l. (1974) nd Sell nd Johnson (1974). The TSAA requirements for ech production prmeter nd their men vlue (0.67%) determined by Nrváez-Solrte et l. (2005) were higher thn vlues determined in the present study. Nrváez-Solrte et l. (2005) used bout 25% sorghum in diet. Investigtions conducted by Rhone-Poulenc Animl Nutrition (1993) showed tht if sorghum tnnin content is higher thn 0.50%, AA digestibility is reduced, which my led to requirement overestimtion. Met nd TSAA requirements estimted in present study (0.30 nd 0.60%, respectively) re very close to those of 0.30 nd 0.58%, respectively reported by NRC (1994). ACKNOWLEDGMENT Our specil thnks to Bu-Ali Sin University for providing fcilities nd finncil support for this study. We lso wish to thnk the stff of the Deprtment of Animl Science of this university for their excellent scientific collbortion. REFERENCES ARC. The nutrient requirements of frm livestock. 2nd ed. London: Agriculturl Reserch Council; 1975. Ahmd HA, Brynt MM. Kucukts S, Rolnd DA. Econometric feeding nd mngement for first cycle phse two Deklb Delt hens. Poultry Science 1997;76:1256-1263. AOAC. Officil methods of nlysis. 15th ed. Wshington: Assocition of Officil Anlyticl Chemists; 1990. Austic RE. 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