Limiting Amino Acids After Methionine and Lysine with Growing Turkeys Fed Low-Protein Diets 1

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1 Limiting Amino Acids After Methionine and Lysine with Growing Turkeys Fed Low-Protein Diets 1 P. E. Waibel, 2 C. W. Carlson, J. A. Brannon, and S. L. Noll Department of Animal Science, University of Minnesota, 1364 Eckles Avenue, St. Paul, Minnesota ABSTRACT The effectiveness of Thr and other amino sulted in reduced BW and breast meat yield (BMY), and acids (AA) replacing CP in Met- and Lys-adequate diets of Large White male turkeys was studied from 6 wk to supplemental Thr or Trp was ineffective in reversing this reduction, and 3) 77 to 79% of NRC CP resulted in depressed BW and BMY. Supplemental Thr provided a sub- market age. Experiment (EXP) 1 examined efficacy of Thr and an AA grouping in corn-soybean (CS) diets containing 82.8 and 77.0% of NRC CP and in corn-soybeanstantial positive BW but no BMY response, whereas a combination of Thr, Ile, Val, Arg, and Trp completely returned BW and partially returned BMY to that of the canola-meat (CSCM) diets containing 85.2 and 79.4% of normal CP control. Turkeys on CS and CSCM assay diet NRC (1984) CP. Experiment 2 compared AA responses series supported BW responses to CP and AA similarly. in CSCM diets containing 100, 92.5, 85, and 77.5% of NRC We concluded that in low-cp diets containing Met and (1994) CP. Compared with control CP, 1) 92.5% of NRC Lys to requirement, supplemental Thr resulted in improved CP supported maximum BW, and supplemental Thr or Trp was without effect; 2) 82.8 to 85.2% of NRC CP re- BW, whereas Thr, Ile, Val, Trp, and Arg returned BW, but not BMY, to normal CP control. (Key words: turkeys, low protein, breast, threonine, tryptophan) 2000 Poultry Science 79: INTRODUCTION Waibel et al. (1995) reported that with sufficient Met and Lys, the needs for other amino acids (AA) were met in corn-soybean (CS) meal-type diets containing 85% of the NRC (1984) CP requirement. Bowyer and Waldroup (1986) and Cabel and Waldroup (1990) noted that performance of turkeys to market age was limited by deficiencies of AA beyond Lys and Met when CP was reduced to less than 90% of NRC (1984). Understandably, these responses may be altered by rate of gain, temperature, and genetics. Studies by Stas and Potter (1982), Jackson et al. (1983), and Blair and Potter (1987) demonstrated that the protein needs of turkey poults fed sufficient Met could be reduced by supplementation with Lys, Thr, Ile, and Val. In a literature review, Kidd and Kerr (1996) concluded that Thr is the third-limiting AA in CS diets for broilers and turkeys and that dietary protein may be reduced with supplementation of Met, Lys, and Thr while sustaining performance. Received for publication September 29, Accepted for publication March 9, Published as Paper No , Scientific Journal Series, Minnesota Agricultural Experiment Station. 2 To whom correspondence should be addressed: waibe001@ tc.umn.edu. 3 British United Turkeys of America, Ltd., Lewisburg, WV Spectam, Rhone Merieux Inc., Athens, GA Direct experimental evidence has not been available on the AA requirements of turkeys over 6 wk of age, beyond Met and Lys. Hurwitz et al. (1983) calculated AA requirements using a modeling procedure based on growth, maintenance, and body composition and reported that the Thr requirements, by 4-wk intervals from day of age, declined from 1.14 to 0.94 to 0.72 to 0.56 to 0.44%. The respective NRC (1994) requirements are 1.0, 0.95, 0.8, 0.75, and 0.6%. The objective of this study, using low protein diets from 6 wk to market age, was to learn the capacity of Thr, Trp, and other AA to return reduced BW gain and breast yield (BMY) to that achieved with normal protein in growing male turkeys. MATERIALS AND METHODS Day-old Large White Male turkey poults (Big 6 3 ) were injected with spectinomycin (10 mg per poult 4 ) and beakand toe-trimmed at the hatchery. In experiments (EXP) 1 and 2 they were fed CS meal starting diets during 0 to 3 and 3 to 6 wk of age (pre-experimental period). At 5 wk they were transferred to a growing barn and assigned equitably to 96 or 98 floor pens ( m) on the Abbreviation Key: AA = amino acids; BMY = breast meat yield; CSCM = corn-soybean-canola-meat; CS = corn-soybean; EXP = experiment; TRT = treatment. 1290

2 AMINO ACIDS FOR TURKEYS 1291 basis of BW. Wood shavings served as litter. There were 12 and 10 turkeys per pen in EXP 1 and 2, allowing and m 2 per bird, respectively. Dietary treatments (TRT) were begun at 6 wk of age. Each TRT was replicated eight times in EXP 1 and seven times in EXP 2. Facility heating and ventilation was by a negative pressure system with gas-fired furnaces and exhaust fans. In EXP 1 room temperatures approximated 19 C from 6 to 20 wk of age (December 6, 1994 through March 13, 1995). In EXP 2 room temperatures ranged from 21 to 26 C from 6 to 20 wk of age (June 27 to October 10, 1995). Diets were adjusted at intervals of 3 wk. The formulation specifications in EXP 1 and 2 were adjusted for equivalence to NRC (1984) and NRC (1994) requirement data, respectively. The diets are presented in Tables 1 through 4. Sodium bicarbonate and potassium chloride were added to avoid excesses of chloride and to meet estimated potassium requirements. Amino acid composition values were as analyzed. Feed formulations were calculated such that nutrient requirements were proportional to diet ME. The two-diet series in EXP 1 (winter study) was CS meal in TRT 1 to 6 (Table 1) and CS-canola-meat (CSCM) in TRT 7 to 12 (Table 2). The diets were formulated to meet the NRC (1984) requirements for Met + Cys and Lys with no minimum for protein. Protein was reduced by constraining Lys. Supplemental Lys was added to low protein TRT such that the level was maintained with age even though the diet level slightly exceeded the NRC requirement. The respective TRT numbers for each diet series, in relation to percentage of NRC Lys, were 1 and 7) 100%; 2 and 8) 87%; 3 and 9) 87% + Thr; 4 and 10) 78%; 5 and 11) 78% + Thr; and 6 and 10) 78% + Thr + Ile + Val + Arg, and, after 16 wk of age, Trp. Supplemental AA levels are shown in Table 5. Averaged over the feeding periods, the 100, 87, and 78% Lys levels for CS and CSCM diet series contained 91.0 or 93.4%, 82.8 or 85.2%, and 77.0 or 79.4% of the stated NRC CP requirement, respectively. In EXP 2, a summer growout study, the Met + Cys and Lys specifications for all TRT were at 107.5% of NRC (1994). The CP levels, in relation to NRC as 100%, by TRT were 1) 107.5%; 2) 100%; 3) as 2 + Thr; 4) 92.5%; 5) as 4 + Thr; 6) as 5 + Trp; 7) 85%; 8) as 7 + Thr; 9) as 8 + Trp; 10) 77.5%; 11) as 10 + Thr; 12) as 11 + Trp; 13) as 12 + Ile, Val, Arg; 14) as 13 + Glu. Diets are in Tables 3 and 4, and supplemental AA levels are in Table 5. Amino acids other than Met + Cys and Lys were added to 100% of NRC, except Thr in TRT 3, which was added to 107.5% of NRC. Tryptophan was added as Tryptosine,5 as described in Table 6; the AA contained therein, other than Trp, were calculated into the diets, except Val, which became slightly higher when added Val was not an intended diet addition. Glutamine was added to achieve equivalent dietary N to TRT 2. The turkeys were weighed individually at the outset of EXP 1 and 2 (6 wk of age), at each change of diets, 5 Archer Daniels Midland Co., Decatur, IL and at EXP completion. Feed consumption data were obtained for each period. The BW averages do not include birds removed because of death, wrong sex, injury, lameness, or pendulous crop. Gains of such birds were included in feed efficiency calculations. At 17 wk of age, litter samples were taken for moisture analyses, and birds were walked about through the pen to record the incidence of problems (lameness, bow legs, knock knees, quick step, shaky leg, or reluctance to move). The turkeys were processed in a commercial processing plant. All birds were subjected to carcass yield evaluations, including boneless breast, thigh and drum, wings, tail, skin, and rack. Only BMY is reported in Tables 5 and 6. Body weight, feed efficiency, and BMY TRT means were analyzed as complete randomized block designs with analysis of variance procedures. Experiment 1 was analyzed using SAS 5.18 (1985) procedures. In addition to error mean square and SEM statistics, probabilities of significance of diet factorial components (diet series and variables), their interactions, and LSD for components are presented in Tables 1 and 2. Statistical analyses for Exp 2 used Statistix 4.0 (1992) and included probability, LSD, error mean square, and SEM statistics. Tukey s w-procedure (Steel and Torrie, 1960) was used to calculate column mean comparisons in each EXP. Experimental units were pens, and blocks comprised localized sections of pens within the EXP facility. RESULTS Experiment 1 (Table 5) Comparison of Diet Series. The BW responses (after 6 wk of age) to protein and AA supplementation within and between the CS and CSCM diet series (TRT 1 to 6 vs. TRT 7 to 12) were similar. The CSCM diet series resulted in reduced feed:gain and litter moisture and greater BMY than the CS series. There were no significant interactions between diet series and protein/aa responses. Combined Diet Series Responses at 82.8 and 85.2% of NRC CP. At 12 wk, turkeys that were fed reduced dietary protein (TRT 2 and 8) had significantly less BW than did those on the control diet (TRT 1 and 7). Although supplemental Thr (TRT 3 and 9) did not result in a BW response, the BW achieved was not different than control. At 20 wk, there were no significant differences among TRT with reduced protein, with or without Thr, and the control. Feed:gain and litter moisture were similar. Breast meat yield was lower with reduced protein and was not affected by Thr supplementation. Combined Diet Series Responses at 77.0 and 79.4% of NRC CP. Birds fed low-protein diets (TRT 4 and 10) exhibited reduced BW and BMY compared with those on control diets (TRT 1 and 7). Addition of Thr (TRT 5 and 11) resulted in a positive BW but not BMY response. Further addition of Ile, Val, and Arg (and Trp from 15 to

3 TABLE 1. Corn-soybean meal series diets of varying protein (Experiment 1) Control, 100% of NRC (1984) Lys 87% of NRC Lys 78% of NRC Lys 91.0% of NRC (1984) CP 82.8% of NRC CP 77.0% of NRC CP Item Ingredients, % Corn, ground yellow Soybean meal, dehulled Animal fat Dicalcium phosphate Calcium carbonate Sodium chloride Potassium chloride Sodium bicarbonate DL-methionine L-lysine HCl Trace mineral mix MNTM Vitamin mix MTS Vitamin mix MTG Choline chloride (50%) Nutrients, % Protein, crude Calcium Phosphorus, inorganic Sodium Potassium Chloride Methionine + cystine Lysine Threonine Valine Isoleucine Tryptophan Arginine ME, kcal/kg 2,994 3,069 3,186 3,253 3,041 3,112 3,223 3,283 3,075 3,142 3,246 3,304 Protein, % of control Protein, % of NRC Age (wk) 1292 WAIBEL ET AL. 1 Trace mineral mixture MNTM contains 2% iron from ferrous sulfate, 0.3% copper from copper sulfate, 6% manganese from manganese sulfate, 6% zinc from zinc oxide, 0.12% iodine from ethylene diamine dihydroiodide, 0.02% cobalt from cobalt carbonate, and 0.161% selenium from sodium selenite. 2 Vitamin mixture MTS-93 supplies (per kilogram of mixture) 4,400,000 IU vitamin A (acetate), 1,650,000 IU vitamin D 3 (cholecalciferol), 5,500 IU vitamin E (acetate), 1.1 g menadione dimethyl pyrimidinol bisulfite, 2.65 g riboflavin, 4.0 g d-calcium pantothenate, 26.5 g niacin, 4 mg vitamin B 12, 0.22 g folic acid, 0.55 g pyridoxine HCl, and 22 mg biotin. 3 Vitamin mixture MTG-74 supplies (per kilogram of mixture): 3,300,000 IU vitamin A (acetate), 1,200,000 IU vitamin D 3 (cholecalciferol), 3,300 IU vitamin E (acetate), 0.77 g menadione dimethyl pyrimidinol bisulfite, 1.98 g riboflavin, 2.6 g d-calcium pantothenate, 20 g niacin, g choline chloride, and 2.76 mg vitamin B 12.

4 TABLE 2. Corn-soybean-canola-meat meal series diets of varying protein (Experiment 1) Control, 100% of NRC (1984) Lys 87% of NRC Lys 78% of NRC Lys 93.4% of NRC (1984) CP 85.2% of NRC CP 79.4% of NRC CP Item Ingredients, % Corn, ground yellow Soybean meal, dehulled Canola meal Meat & bone meal Animal fat Dicalcium phosphate Calcium carbonate Sodium chloride Potassium chloride Sodium bicarbonate DL-methionine L-lysine HCL Trace mineral mix MNTM Vitamin mix MTS Vitamin mix MTG Nutrients, % Protein, crude Calcium Phosphorus, inorganic Sodium Potassium Chloride Methionine + cystine Lysine Threonine Valine Isoleucine Tryptophan Arginine ME, kcal/kg 3,019 3,092 3,208 3,273 3,067 3,136 3,244 3,304 3,101 3,166 3,266 3,322 Protein, % of Control Protein, % of NRC Trace mineral mixture MNTM contains 2% iron from ferrous sulfate, 0.3% copper from copper sulfate, 6% manganese from manganese sulfate, 6% zinc from zinc oxide, 0.12% iodine from ethylene diamine dihydroiodide, 0.02% cobalt from cobalt carbonate, and 0.161% selenium from sodium selenite. 2 Vitamin mixture MTS-93 supplies (per kilogram of mixture) 4,400,000 IU vitamin A (acetate), 1,650,000 IU vitamin D 3 (cholecalciferol), 5,500 IU vitamin E (acetate), 1.1 g menadione dimethyl pyrimidinol bisulfite, 2.65 g riboflavin, 4.0 g d-calcium pantothenate, 26.5 g niacin, 4 mg vitamin B 12, 0.22 g folic acid, 0.55 g pyridoxine HCl, and 22 mg biotin. 3 Vitamin mixture MTG-74 supplies (per kilogram of mixture): 3,300,000 IU vitamin A (acetate), 1,200,000 IU vitamin D 3 (cholecalciferol), 3,300 IU vitamin E (acetate), 0.77 g menadione dimethyl pyrimidinol bisulfite, 1.98 g riboflavin, 2.6 g d-calcium pantothenate, 20 g niacin, g choline chloride, and 2.76 mg vitamin B 12. Age (wk) AMINO ACIDS FOR TURKEYS 1293

5 TABLE 3. Diets of varying protein/amino acids from 6 to 15 wk of age (Experiment 2) 6 to 9 wk 9 to 12 wk 12 to 15 wk % of NRC CP Item Ingredients, % Corn, ground yellow Soybean meal, dehulled Canola meal Meat and bone meal Animal fat Dicalcium phosphate Calcium carbonate Sodium chloride Potassium chloride Sodium bicarbonate DL-methionine L-lysine HCl Trace mineral mix MNTM Vitamin mix MTS Vitamin mix MTG Choline chloride (50%) Nutrients, % Protein, crude Calcium Phosphorus, inorganic Sodium Potassium Chloride Methionine + cystine Lysine Threonine Valine Isoleucine Tryptophan Arginine ME, kcal/kg 2,970 3,008 3,047 3,087 3,127 3,060 3,095 3,130 3,166 3,201 3,151 3,183 3, WAIBEL ET AL. 1 Trace mineral mixture MNTM contains 2% iron from ferrous sulfate, 0.3% copper from copper sulfate, 6% manganese from manganese sulfate, 6% zinc from zinc oxide, 0.12% iodine from ethylene diamine dihydroiodide, 0.02% cobalt from cobalt carbonate, and 0.161% selenium from sodium selenite. 2 Vitamin mixture MTS-93 supplies (per kilogram of mixture) 4,400,000 IU vitamin A (acetate), 1,650,000 IU vitamin D 3 (cholecalciferol), 5,500 IU vitamin E (acetate), 1.1 g menadione dimethyl pyrimidinol bisulfite, 2.65 g riboflavin, 4.0 g d-calcium pantothenate, 26.5 g niacin, 4 mg vitamin B 12, 0.22 g folic acid, 0.55 g pyridoxine HCl, and 22 mg biotin. 3 Vitamin mixture MTG-74 supplies (per kilogram of mixture): 3,300,000 IU vitamin A (acetate), 1,200,000 IU vitamin D 3 (cholecalciferol), 3,300 IU vitamin E (acetate), 0.77 g menadione dimethyl pyrimidinol bisulfite, 1.98 g riboflavin, 2.6 g d-calcium pantothenate, 20 g niacin, g choline chloride, and 2.76 mg vitamin B 12.

6 TABLE 4. Diets of varying protein from 12 to 21 wk of age (Experiment 2) 12 to 15 wk 15 to 18 wk 18 to 21 wk (% of NRC CP) Item Ingredients, % Corn, ground yellow Soybean meal, dehulled Canola meal Meat and bone meal Animal fat Dicalcium phosphate Calcium carbonate Sodium chloride Potassium chloride Sodium bicarbonate DL-methionine L-lysine HCl Trace mineral mix MNTM Vitamin mix MTG Nutrients, % Protein, crude Calcium Phosphorus, inorganic Sodium Potassium Chloride Methionine + cystine Lysine Threonine Valine Isoleucine Tryptophan Arginine ME, kcal/kg 3,247 3,280 3,212 3,241 3,271 3,300 3,328 3,267 3,293 3,320 3,346 3,372 1 Trace mineral mixture MNTM contains 2% iron from ferrous sulfate, 0.3% copper from copper sulfate, 6% manganese from manganese sulfate, 6% zinc from zinc oxide, 0.12% iodine from ethylene diamine dihydroiodide, 0.02% cobalt from cobalt carbonate, and 0.161% selenium from sodium selenite. 2 Vitamin mixture MTG-74 supplies (per kilogram of mixture): 3,300,000 IU vitamin A (acetate), 1,200,000 IU vitamin D 3 (cholecalciferol), 3,300 IU vitamin E (acetate), 0.77 g menadione dimethyl pyrimidinol bisulfite, 1.98 g riboflavin, 2.6 g d-calcium pantothenate, 20 g niacin, g choline chloride, and 2.76 mg vitamin B 12. AMINO ACIDS FOR TURKEYS 1295

7 1296 WAIBEL ET AL. TABLE 5. Effect of diet, protein, and amino acids (AA) on performance of turkeys (Experiment 1) BW Litter Breast Diet protein, % of NRC (1984) Feed:gain moisture meat of Treatment (TSAA and Lys at 100% NRC) 12 wk 20 wk 6 20 wk 17 wk carcass (kg) (g:g) (%) Corn-soy series (CS) 1 Control, 91% % As % Thr % As % Thr As 5 + AA Corn-soy-canola-meat series (CSCM) 7 Control, 93.4% % As % Thr % As % Thr As 11 + AA Summary by diet series (S) CS CSCM Summary by protein/aa (PAA) 1, 7 Control 7.07 a a a a a 2, and 85.2% of NRC CP 6.86 b ab ab ab bc 3, 9 As 2, % Thr 6.96 ab a ab a b 4, and 79.4% of NRC CP 6.53 c c a b c 5, 11 As 4, % Thr 6.86 b b ab ab c 6, 12 As 5,11 + AA a a b ab b Statistical analysis P of significance For all 12 treatments < < < Between S Between PAA < < < S PAA Least significant differences (P < 0.05) For all treatments Between S Between PAA PAA (By Tukey w-procedure) Error mean square SEM a c Column means followed by noncommon letter are significantly different at P = 0.05 by Tukey s multiple comparison test. 1 Amino acids: Ile, Val, and Arg at 0.15% from 6 to 20 wk and Trp at 0.025% from 15 to 20 wk. 2 These CSCM and CS factorial diet series means are significantly different at P = wk) resulted in a further gain response, such that BW was returned to that of control. Breast meat yield was also increased with the combination of AA but not to the level of the control. Feed:gain was improved with combined low protein and AA supplementation (TRT 6 and 12) compared with control (TRT 1 and 7). Litter moisture was reduced with low protein (TRT 4 and 10) compared with control (TRT 1 and 7). Incidence of mortality was low (1.7%) and not related to TRT. Incidence of leg problems was also low (4.2%) and not related to TRT. Experiment 2 (Table 6) Responses at 100 and 107.5% of NRC CP. At 12, 18, and 21 wk of age (EXP begun at 6 wk), turkeys fed 100% of NRC CP, with or without added Thr (TRT 2 and 3), were equivalent in BW to turkeys fed 107.5% NRC CP (TRT 1). This equivalence extended to BMY at processing. Responses at 92.5% of NRC CP. At 92.5% CP (TRT 4), BW was similar compared with 100% CP (TRT 2; as was BMY using Tukey s test). Breast meat yield was depressed when the standard LSD value of 0.71% was used; this interpretation is supported when comparing yields of TRT 4 to 6 (92.5% CP) with TRT 1 to 3 (100 and 107.5% CP). Added Thr or Thr + Trp did not result in altered performance at 92.5% CP. Responses at 85% of NRC CP. The BW and BMY were reduced at 21 wk with 85% of NRC CP (TRT 7) compared with 100% CP (TRT 2). Addition of Thr (TRT 8) or Thr + Trp (TRT 9) did not affect these results. Responses at 77.5% of NRC CP. Body weight, feed efficiency, and BMY were reduced markedly at 77.5% of NRC CP (TRT 10) in comparison with the control (TRT 2). The Thr supplementation alone (TRT 11) improved BW but not BMY. Addition of Trp (TRT 12) to Thr (TRT 11) was without effect.

8 AMINO ACIDS FOR TURKEYS 1297 Excellent improvements in BW, feed efficiency, and BMY resulted from addition of Ile, Val, and Arg (TRT 13) to Thr and Trp (TRT 12). Body weight was similar to that of control (TRT 2), as was BMY using Tukey s test. It is noted that BMY fell short of control when the standard LSD was employed, which concurred with the Tukey significant findings in EXP 1. Feed:gain was superior with additionally-supplemented AA (TRT 13) compared with control (TRT 2). Additional Glu generally reduced performance, but not significantly. Mortality was low (average 1.6%) and not related to TRT. Incidence of leg problems averaged 2.7% with no significant differences among TRT. Litter moisture values among TRT were interesting but did not result in any significant differences using Tukey s test. DISCUSSION Generally, Met and Lys are first- and second-limiting AA in CS meal diets for turkeys. Thr is often considered the third-limiting AA (Kidd and Kerr, 1996). Because of variation in dietary protein and in requirements, it is not possible to be certain of a given order of AA limitation. Kidd et al. (1997) observed that reduced performance with 85% of CP was reversed by supplementation of 0.10% Thr in growing turkeys at 18 wk of age. The results in present EXP 1 and 2 at market age show that at 77 to 79% of NRC CP (with adequate Met and Lys) Thr provided substantial BW responses, which were inferior to the complete BW recovery obtained with Thr, Ile, Val, Trp, and Arg. In EXP 2, BMY was depressed at 85% of NRC CP, and here Thr did not reverse this depression. The dilemma whether an identified limiting AA can provide complete BW recovery makes it important to have accurate AA requirement data for next-limiting AA, in this case Val, Ile, Trp, and Arg. To obtain this requirement much research is needed, considering the changing needs of growing market turkeys and the reported influence of protein level on AA requirements. This was not a requirement study, but it was an attempt to study assay diets for future requirement study efforts. The following Thr requirement studies of Lehmann et al. (1997), Waldroup et al. (1998), and Kidd et al. (1998) are included to help understand the Thr responses obtained herein. TABLE 6. Response of male turkeys to dietary protein/amino acids from 6 to 21 wk of age (Experiment 2) 1 BW % of NRC (1994) protein 2 Feed:gain Breast Item with added amino acids Week 12 Week 18 Week 21 6 to 21 wk meat Treatment (kg) (g:g) (% of carcass) ab a abcd bc a (control) 6.93 a a a c a Thr a a ab cd a a a abc cd ab Thr a ab abcd cd ab Thr + TRPS 5, a a abcd cd ab b b cd c b Thr ab ab d cd bc Thr + TRPS ab ab bcd cd bc c d f a c Thr b bc e ab c Thr + TRPS b c e b c 13 As TRT 12 + Ile, Val, Arg a a a d ab 14 As TRT 13 + Glu ab ab abcd d bc Statistics P value < < < < < Least significant difference (P = 0.05) Tukey w-procedure Error mean square SEM a f Values followed by non-common letter within column were different by Tukey s test at P = Treatment mean weights at 8 wk of age averaged 3.69 kg (range 3.68 to 3.70 kg). 2 All treatments contained methionine and lysine supplementation such that methionine + cystine and lysine levels were brought to 107.5% of NRC (1994). 3 Supplementary Thr levels (%) in respective periods were 0.072, 0.136, 0.065, 0.055, Supplementary Thr levels (%) in respective periods were 0.154, 0.142, 0.065, 0.056, TRPS (Tryptosine feed supplement) contains (in %) Trp, 10; Lys, 47.5; Met, 3.5; Cys, 2.5; Val, 1; and Thr, Supplementary TRPS levels (%) in respective periods were 0.044, 0.118, 0.232, 0.195, and Supplementary Thr levels (%) in respective periods were 0.237, 0.215, 0.131, 0.114, and Supplemental TRPS levels (%) in respective periods were 0.336, 0.375, 0.470, 0.406, and Supplemental Thr levels (%) in respective periods were 0.323, 0.289, 0.197, 0.173, and Supplemental TRPS levels (%) in respective periods were 0.637, 0.637, 0.713, 0.621, and Added (% per respective period): Ile 0.316, 0.294, 0.250, 0.221, and 0.202; Val 0.294, 0.259, 0.246, 0.217, and 0.197; and Arg HCl 0.483, 0.469, 0.473, 0.420, and Supplemental Glu levels (%) in respective periods were 8.45, 7.27, 6.60, 5.88, and 5.28.

9 1298 WAIBEL ET AL. Lehmann et al. (1997) quantified gain responses to Thr using BUT Big 6 tom turkeys during 0 to 4, 8 to 12, and 16 to 20 wk of age. Their requirement estimate of 1.8 g Thr/Mcal ME during 16 to 20 wk of age indicates that in the present study Thr was marginally deficient in the 83 to 85% of NRC CP diets and quite deficient in the 77% of NRC CP diets. The Waldroup et al. (1998) requirement estimate of 2.87 g Thr/Mcal ME from 6 to 9 wk is high compared with the Lehmann et al. (1997) value of 2.2 g/mcal ME. From 6 to 9 wk in EXP 2 of the present study, Thr did not result in improved BW at 85 or 92.5% but did improve at 77.5% of NRC CP, suggesting that 2.51 g Thr/Mcal ME was adequate and 2.25 g Thr/Mcal ME was deficient. This result agrees with the requirement data of Kidd et al. (1998), which indicated a requirement of 2.30 g Thr/Mcal ME from 6 to 9 wk of age. The role of Trp in these studies is of interest because of the increasing dependence on protein from corn in age-appropriate diets. There were no responses to Trp in either BW gain or BMY at 92.5 or 85% of NRC protein (EXP 2). When Trp was added at 77.5% of NRC protein, inspection of the BW gain data (TRT 11 and 12) shows no benefit in promotion of BW gain at 18 wk; however, there is the suggestion of a BW gain stimulation between 18 to 21 wk. This response, combined with a 0.57% improvement in breast yield, suggests that Trp may become important at this age and protein level. The inability of AA supplementation to bring breast proportion to that of control is problematic. Deschepper and De Groote (1995) reported that in broilers AA balance was important in achievement of performance with low protein; they found that although gains were similar, the low-protein diet resulted in higher carcass fat content. Bartov and Plavnik (1998) observed, also with broilers, that a moderate excess of dietary protein above the NRC (1994) recommendation was effective in simultaneously increasing BMY and reducing abdominal fat. The turkey would appear to be a good model in study of the relationship between protein level and meat formation proportionality. The reduction in dietary AA N made possible by AA supplementation will help to reduce N in poultry waste, with attendant reduction in pollution of the environment. Unfortunately, the cost of such AA supplementation is presently prohibitive. It is important to learn the interrelationships involved because by the time they are known there may be means available to achieve this ecological goal. ACKNOWLEDGMENTS This study was supported in part by the Midwest Poultry Consortium through funding from the Minnesota Turkey Research and Promotion Council, St. Paul, MN 55114, and Archer Daniels Midland Co., Decatur, IL Meat and bone meal was supplied by Central By-Products, Redwood Falls, MN 56283; canola meal by Canamera Foods, Winnipeg, Manitoba R3H1B3; Met by Degussa Corp., Ridgewood Park, NJ 07660; dicalcium phosphate by Pitman-Moore, Mundelin, IL 60060; and Lys, Thr, Arg, Ile, Val, and Trp by ADM Co., Decatur, IL Degussa Corp. performed feedstuff AA analyses. Appreciation is expressed to Mark Sandstrom and Ken Mainz of the Rosemount Agricultural Experiment Station and to Frank Martin, Department of Applied Statistics, for their support. REFERENCES Bartov, I., and I. Plavnik, Moderate excess of dietary protein increases breast meat yield in broiler chicks. Poultry Sci. 77: Blair, M. E., and L. M. Potter, Deficient AA in protein in dehulled soybean meal for young turkeys. 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