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Digestible lysine requirements of male broilers from 28 to 42 days of age1
Digestible lysine requirements of male broilers from 28 to 42 days of age1 W. A. Dozier III,*2 A. Corzo,† M. T. Kidd,† P. B. Tillman,‡ J. P. McMurtry,§ and S. L. Branton# *Department of Poultry Science, Auburn University, Auburn, AL 38649; †Department of Poultry Science, Mississippi State University, Mississippi State, MS 39762; ‡Ajinomoto Heartland LLC, Chicago, IL 60631; §USDA-Agricultural Research Service, Animal and Natural Resources Institute, Beltsville, MD 20705; and #USDA-Agricultural Research Service, Poultry Research Unit, Mississippi State, MS 39762 were estimated using a quadratic broken-line model. In experiment 1, the digestible Lys requirement for male Ross × Ross TP16 broilers was determined at 0.988, 1.053, 0.939, and 0.962%, respectively, for BW gain, feed conversion, carcass weight, and total breast meat weight. In experiment 2, the digestible Lys requirement for male Cobb × Cobb 700 broilers ranged from 0.965, 1.012, 1.029, 0.987, and 0.981%, respectively, for 28- to 42-d BW gain, feed conversion, carcass weight, total breast meat weight, and total breast meat yield. Digestible Lys requirements for male Ross × Ross TP16 and Cobb × Cobb 700 broilers were estimated at 1.001 and 0.995%, respectively, based upon averages of live performance and meat yield responses. Both strains required the highest requirement estimate of digestible Lys to optimize feed conversion.
Key words: broiler, lysine, live performance, carcass part, physiological variable 2010 Poultry Science 89:2173–2182 doi:10.3382/ps.2010-00710
INTRODUCTION Lysine is typically the second-limiting amino acid for broiler chickens. Defining the optimum Lys requirement is economically important because feeding diets either deficient or in excess of Lys need can translate to poor performance or increased diet cost. Today’s highperforming broiler consumes less feed per unit of BW gain than birds of previous decades (Havenstein et al., 2003a,b; Dozier et al., 2008a,b). The modern broiler responds to higher dietary amino acid levels than the commercial broiler used in previous decades due to improvements in genetic selection, such as decreased feed intake per unit of BW gain and greater accretion rate ©2010 Poultry Science Association Inc. Received February 16, 2010. Accepted June 27, 2010. 1 Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by Auburn University, Mississippi State University, or the USDA. 2 Corresponding author: [email protected]
for meat yield (Kidd et al., 2004; Dozier et al., 2008b, 2009a; Corzo et al., 2009). Dozier et al. (2009a) reported that the digestible Lys requirement for male broilers from 14 to 28 d of age was 18% higher than the NRC (1994) recommendations. Moreover, these authors determined a 162% increase in 14- to 28-d BW gain than that reported by NRC (1994). The increased BW gain of the modern broiler suggests higher amino acid needs compared with birds used in previous research. Dietary Lys requirement has been evaluated more extensively in the starter (Han and Baker, 1991; Knowles and Southern, 1998; Labadan et al., 2001; Baker et al., 2002; Sklan and Noy, 2003; Garcia and Batal, 2005) and less extensively in the grower (Labadan et al., 2001; Dozier et al., 2009a), finisher (Han and Baker, 1994; Leclercq, 1998; Mack et al.,1999), and withdrawal (Corzo et al., 2002, 2006; Dozier et al., 2008a) periods. Dietary Lys requirement is dependent upon the response criteria, with requirements often being the highest for feed conversion (Han and Baker, 1994; Leclercq, 1998; Mack et al., 1999; Baker et al., 2002; Corzo et
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ABSTRACT Research addressing digestible Lys requirement data of modern broilers from 4 to 6 wk of age is limited. Male broilers (1,632 Ross × Ross TP16 and 3,000 Cobb × Cobb 700) were used in separate experiments to determine the digestible Lys requirements from 28 to 42 d. In each experiment, 2 diets (dilution and summit) consisting of corn, soybean meal, animal protein meal, and peanut meal were formulated to be adequate in all other amino acids. The dilution and summit diets were blended to create 9 titration diets. A control diet formulated to contain corn, soybean meal, and animal protein meal as the primary ingredients was used for comparison with the titration diets. Body weight gain, feed intake, digestible Lys intake, digestible Lys intake:BW gain, feed conversion, mortality, carcass yields, and physiological measurements were assessed during experimentation. Digestible Lys requirements
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MATERIALS AND METHODS Dietary Treatments Ten experimental diets were fed from 28 to 42 d of age consisting of 9 graded concentrations of digestible Lys plus a positive control. Two diets consisting of corn, soybean meal, animal protein meal, and peanut meal were formulated to meet or exceed NRC (1994) nutrient requirements (Tables 1 and 2). Diets were formulated based on amino acid ratios to ensure adequacy of essential amino acids so the digestible Lys response would not be limited. The 2 diets were mixed in varying proportions to create 9 dose-response diets ranging from 0.64 to 1.20% digestible Lys in 0.07% increments. Diet dilution technique was used as the high-Lys diet was formulated to contain 0.71% of l-Lys·HCl and the low-Lys diet contained no added l-Lys·HCl. Treatment differences were not due solely to digestible Lys percentage from added l-Lys-HCl because the amount of corn, soybean meal, poultry oil, Gly, and l-Glu differed between the low-Lys and the high-Lys diets in experiment 1 (Table 1). In experiment 2, the diets differed in the content of ground corn and Gly (Table 2). The control diet was formulated to contain 0.99% digestible Lys and was used to validate the dose-response diet (0.99% digestible Lys level). Corn, soybean meal, animal protein meals, and peanut meal were analyzed for total amino acids (methods 985.28 and 994.12; AOAC, 2006) and CP (method 968.06; AOAC, 2006) composi-
tion before diet formulation. Digestible amino acid values were determined from digestible coefficients (Ajinomoto Heartland LLC, 2009) and analyzed total amino acid content of the ingredients. Digestible TSAA, Thr, Val, Ile, Arg, and Trp ratios to Lys were formulated based on a modification of digestible ratios reported by Lemme et al. (2004), with the ratios being increased by 2 percentage points to ensure that these essential amino acids were not limiting. Digestibility coefficients for ingredients were subtracted by 0.5 of the SD to add a margin of safety. Digestibility coefficients for corn, soybean meal, meat and bone meal, peanut meal, and poultry by-product meal were based on 45, 85, 124, 7, and 57 sample assays, respectively. Diets were manufactured as pellets. Representative samples were obtained to validate the dietary Lys concentrations of the experimental diets (Table 3).
Experiments 1 and 2 All procedures relating to the use of live birds were approved by the USDA-Agricultural Research Service Animal Care and Use Committee at the Mississippi State location and Auburn University Institutional Animal Care and Use Committee. Ross × Ross TP16 and Cobb × Cobb 700 male broiler chicks (experiment 1 = 1,632; experiment 2 = 3,000) were obtained from a primary breeder hatchery and were vaccinated for Marek’s disease, Newcastle disease, and infectious bronchitis. Experiments were conducted at the USDA-Agricultural Research Service Poultry Research Unit at Mississippi State (Ross × Ross TP16 strain) and at Auburn University (Cobb × Cobb 700 strain); hence, location and strain differences make comparison between studies difficult. Chicks were reared in a solid-side wall facility and were fed common diets until 28 d of age (starter = digestible TSAA, 0.92%; digestible Lys, 1.22%; digestible Thr, 0.83%; CP, 23.0%; AMEn, 3,075 kcal/ kg; grower = digestible TSAA, 0.86%; digestible Lys, 1.13%; digestible Thr, 0.74%; CP, 20.9%; AMEn, 3,140 kcal/kg). At 28 d of age, chicks were equalized among floor pens (0.09 m2/bird; experiment 1 = 15 birds/pen; experiment 2 = 23 birds/pen). Each pen was equipped with a hanging feeder, a nipple drinker line, and used litter. Birds consumed feed and water on an ad libitum basis and experimental diets were provided in whole pellet form. Ambient temperature set points consisted of 33°C at placement until 4 d of age, 32°C from 5 to 9 d of age, 29°C from 10 to 14 d of age, 27°C from 15 to 23 d of age, 25°C from 24 to 28 d of age, 23°C from 29 to 33 d of age, 21°C from 34 to 38 d of age, and 19°C from 39 to 42 d of age. Actual average ambient temperatures during experimentation were 23.6°C ± 1.2 SD for experiment 1 and 23.1°C ± 3.0 SD for experiment 2. Photoperiod was a continuous schedule with lighting intensities of 30 lx from 0 to 7 d of age, 10 lx from 8 to 12 d of age, and 3 lx from 23 to 28 d of age for Ross × Ross TP16 male broilers in experiment 1 and the lighting schedule for experiment 2 consisted of a 23L:1D
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al., 2006; Dozier et al., 2008a, 2009a). Leclercq (1998) reported the total Lys requirements at 0.92, 0.97, and 1.01%, respectively, for BW gain, breast meat yield, and feed conversion for 20- to 40-d-old male broilers. Han and Baker (1994) determined the digestible Lys requirement for 21- to 42-d-old male broilers at 0.89% for feed conversion; however, a requirement for BW gain was estimated to be 0.85%. In addition, Mack et al. (1999) estimated dietary Lys requirements of Ross and ISA broilers from 20 to 40 d of age at 0.95 and 0.89%, respectively, using feed conversion as the response criterion. In commercial practice, market weights and anticoccidial programs often dictate feeding schedules. Daily growth rate typically reaches a maximum from 4 to 6 wk of age during the life cycle of the broiler (Simmons et al., 2003), and this age interval coincides with finishing periods. In addition, approximately 43% of the broilers marketed in the US industry are 2.9 kg or greater. Research determining the digestible Lys requirement in modern broilers from 1.5 to 3.0 kg of BW is sparse. Research reported herein evaluated digestible Lys requirements of Ross × Ross TP16 and Cobb × Cobb 700 male broilers. Measurements encompassed live performance, yields of carcass parts, and physiological variables such as plasma insulin-like growth factor I (IGF-I), blood urea nitrogen, and uric acid concentrations.
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DIETARY LYSINE NEEDS OF BROILERS Table 1. Ingredient and calculated composition of diets provided during a 28- to 42-d production period, experiment 1 Low Lys
High Lys
Control
Ingredient, % as fed Ground corn Soybean meal (48% CP) Peanut meal (41% CP) Poultry by-product meal Poultry oil Dicalcium phosphate Calcium carbonate Sodium chloride Sodium bicarbonate dl-Met l-Lys·HCl l-Thr l-Val l-Ile l-Arg l-Trp Gly l-Glu Choline chloride Vitamin and mineral premix1 Coccidiostat2 Calculated analysis AMEn, kcal/kg CP, % Digestible TSAA, % Digestible Lys, % Digestible Thr, % Digestible Ile, % Digestible Val, % Digestible Trp, % Digestible Arg, % Digestible TSAA:Lys ratio Digestible Thr:Lys ratio Digestible Val:Lys ratio Digestible Ile:Lys ratio Digestible Arg:Lys ratio Digestible Trp:Lys ratio Ca, % Nonphytate P, % Na, %
70.30 11.91 7.50 2.69 2.40 1.33 0.90 0.13 0.40 0.46 — 0.31 0.25 0.25 0.20 0.07 0.33 0.33 0.06 0.13 0.05 3,186 17.75 0.92 0.64 0.81 0.81 0.92 0.20 1.25 144 127 144 127 196 32 0.84 0.42 0.23
69.80 12.16 7.50 2.69 2.22 1.33 0.90 0.13 0.40 0.46 0.71 0.31 0.25 0.25 0.20 0.07 0.19 0.19 0.06 0.13 0.05 3,186 18.25 0.92 1.20 0.81 0.81 0.92 0.20 1.25 77 68 77 68 105 17 0.84 0.42 0.23
69.51 20.80 — 4.00 2.47 1.11 0.84 0.32 0.25 0.23 0.17 0.06 — — — — — 0.06 0.13 0.05 3,186 18.20 0.77 0.99 0.67 0.67 0.77 0.17 1.10 78 68 78 68 111 17 0.84 0.42 0.22
1Vitamin and mineral premix included the following per kilogram of diet: vitamin A (vitamin A acetate), 4,960 IU; vitamin D (cholecalciferol), 1,653 IU; vitamin E (dl-α-tocopherol acetate), 27 IU; menadione (menadione sodium bisulfate complex), 0.99 mg; vitamin B12 (cyanocobalamin), 0.015 mg; folic (folic acid), 0.8 mg; d-pantothenic acid (calcium pantothenate), 15 mg; riboflavin (riboflavin), 5.4 mg; niacin (niacinamide), 45 mg; thiamin (thiamin mononitrate), 2.7 mg; d-biotin (biotin), 0.07 mg; pyridoxine (pyridoxine hydrochloride), 5.3 mg, Mn (manganous oxide), 90 mg; Zn (zinc oxide), 83 mg; Fe (iron sulfate monohydrate), 121 mg; Cu (copper sulfate pentahydrate), 12 mg; I (calcium iodate), 0.5 mg; and Se (sodium selenite), 0.3 mg. 2BioCox 60 provided 60 g/907 kg of salinomycin from Alpharma (Fort Lee, NJ).
photoperiod with an intensity of 30 lx from 0 to 7 d of age, 18L:6D photoperiod with an intensity of 10 lx from 8 to 12 d of age, 15L:9D photoperiod with an intensity of 5 lx from 13 to 28 d of age, 18L:6D photoperiod with an intensity of 2.5 lx from 29 to 39 d of age, and 23L:1D photoperiod with an intensity of 2.5 lx from 40 to 42 d of age for Cobb × Cobb 700 male broilers in experiment 2. Light intensity settings were verified at bird level (30 cm) using a photometric sensor with National Institute of Standards and Technology-traceable calibration (403125, Extech Instruments, Waltham, MA) for each intensity adjustment. Birds and feed were weighed on d 28 and 42 for the determination of BW gain, feed intake, digestible Lys intake, digestible intake:BW gain, and feed conversion. Mortality was recorded daily.
On d 43, five birds per pen were randomly selected for processing, weighed, placed in coops, and transported to a pilot poultry processing plant (experiment 1 = Mississippi State University; experiment 2 = Auburn University). Feed was removed 12 h before processing. Birds were electrically stunned, bled, scalded, picked, and mechanically eviscerated. Whole carcass (without abdominal fat) and abdominal fat were weighed. Carcasses were split into front and back halves and placed on ice for 18 h. Afterward, the front halves were deboned to obtain weights of pectoralis major and minor muscles. Carcass, abdominal fat, and total breast meat (pectoralis major and minor muscles) yields were expressed as a percentage of 43-d BW of selected broilers.
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Blood Analysis Experiment 1. On d 39, blood was collected via the ulnar vein [heparinized (4.5 mL; 50 IU/mL−1) monovette syringe equipped with a 20-gauge needle that was 25.4 mm in length] from 2 birds per pen of 7 replicates from broilers fed dose-response diets formulated to 0.64, 0.99, and 1.20% digestible Lys directly into tubes containing EDTA. Plasma concentrations of IGF-I were determined using RIA as described by McMurtry et al. (1994). Samples were analyzed in a single assay to avoid interassay variation and the CV was 3.9%.
Experiment 2. Plasma urea nitrogen and uric acid were measured in this experiment as response criteria for determining the digestible Lys requirement. On d 44, blood was collected from 2 birds from 6 replicate pens of birds receiving the 10 dietary treatments via the ulnar vein directly into a heparinized (50 IU/mL−1) monovette syringe. Samples from each bird were centrifuged at 2,000 × g for 5 min and 1 mL of plasma was obtained and stored at −20°C for later analysis. Plasma concentrations of blood urea nitrogen (Talke and Schubert, 1965) and uric acid (Town et al., 1985) were determined using an auto chemistry analyzer (Hitachi 911, Roche Diagnostics, Indianapolis, IN).
Table 2. Ingredient and calculated composition of diets provided during a 28- to 42-d production period, experiment 2 Low Lys
High Lys
Control
Ingredient, % as fed Ground corn Soybean meal (48% CP) Peanut meal (41% CP) Meat and bone meal Poultry oil Defluorinated phosphate Calcium carbonate Sodium chloride Sodium bicarbonate dl-Met l-Lys·HCl l-Thr l-Val l-Ile l-Arg l-Trp Gly Mineral premix1 Vitamin premix2 Phytase3 Coccidiostat4 Calculated analysis AMEn, kcal/kg CP, % Digestible TSAA, % Digestible Lys, % Digestible Thr, % Digestible Ile, % Digestible Val, % Digestible Trp, % Digestible Arg, % Digestible TSAA:Lys ratio Digestible Thr:Lys ratio Digestible Val:Lys ratio Digestible Ile:Lys ratio Digestible Arg:Lys ratio Digestible Trp:Lys ratio Ca, % Nonphytate P, % Na, %
67.51 15.39 7.50 3.00 1.65 0.33 1.15 0.10 0.48 0.52 — 0.34 0.29 0.30 0.22 0.08 0.57 0.25 0.25 0.02 0.05 3,125 18.65 0.92 0.64 0.80 0.83 0.92 0.22 1.28 144 125 144 129 199 33 0.88 0.44 0.22
67.36 15.39 7.50 3.00 1.65 0.33 1.15 0.10 0.48 0.52 0.72 0.34 0.29 0.30 0.22 0.08 — 0.25 0.25 0.02 0.05 3,125 18.65 0.92 1.20 0.80 0.83 0.92 0.22 1.28 77 67 77 69 107 18 0.88 0.44 0.22
62.79 28.23 — 3.00 2.91 0.27 1.15 0.33 0.30 0.27 0.12 0.06 — — — — — 0.25 0.25 0.02 0.05 3,125 19.55 0.76 0.99 0.66 0.68 0.79 0.19 1.16 77 67 77 69 107 18 0.88 0.44 0.22
1Mineral premix included the following per kilogram of diet: Mn (manganous oxide), 65 mg; Zn (zinc oxide), 55 mg; Fe (iron sulfate monohydrate), 55 mg; Cu (copper sulfate pentahydrate), 6 mg; I (calcium iodate), 1 mg; and Se (sodium selenite), 0.3 mg. 2Vitamin premix included the following per kilogram of diet: vitamin A (vitamin A acetate), 8,000 IU; vitamin D (cholecalciferol), 2,000 IU; vitamin E (dl-α-tocopherol acetate), 8 IU; menadione (menadione sodium bisulfate complex), 2 mg; vitamin B12 (cyanocobalamin), 0.02 mg; folic (folic acid), 0.5 mg: d-pantothenic acid (calcium pantothenate), 15 mg; riboflavin (riboflavin), 5.4 mg; niacin (niacinamide), 45 mg; thiamin (thiamin mononitrate), 1 mg; d-biotin (biotin), 0.05 mg; pyridoxine (pyridoxine hydrochloride), 2.2 mg; and choline (choline chloride), 500 mg. 3Quantum Phytase from AB Vista (Marlborough, Wiltshire, UK). 4BioCox 60 provided 60 g/907 kg of salinomycin from Alpharma (Fort Lee, NJ).
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RESULTS Experiment 1 Ross × Ross TP16 male broilers fed gradient concentrations of digestible Lys displayed significant (P ≤ 0.05) quadratic responses for BW, BW gain, feed intake, Lys intake, Lys intake:BW gain, feed conversion, carcass weight, and total breast meat weight (Tables 4 and 5). Linear responses (P ≤ 0.03) were observed for
abdominal fat weight, abdominal fat percentage, and breast meat yield. Plasma IGF-I concentrations (grand mean = 38.49 µmol/L ± 1.78 SEM; data not shown) were not different (P > 0.05) from broilers fed diets formulated to contain 0.64, 0.99, or 1.20% digestible Lys. Control-fed broilers grew faster (P ≤ 0.002) and consumed more feed (P ≤ 0.001) than broilers fed the dose-response diet formulated to 0.99% digestible Lys, but other variables measured were similar (P > 0.05). Digestible Lys requirements were estimated at 0.988, 1.053, 0.939, 0.921, and 0.962%, respectively, for BW gain, feed conversion, carcass weight, carcass yield, and total breast weight based on quadratic broken-line methodology (Table 6).
Experiment 2 Feeding Cobb × Cobb 700 male broilers progressive concentrations of digestible Lys resulted in quadratic responses (P ≤ 0.02) in BW, BW gain, feed intake, Lys intake, Lys intake:BW gain, feed conversion, carcass weight, carcass yield, total breast meat, and total breast meat yield, and linear responses (P ≤ 0.04) were observed for abdominal fat weight, abdominal fat percentage, and plasma uric acid concentration (Tables 7 and 8; Figure 1). Plasma nitrogen (grand mean = 2.44 mg/dL ± 0.18 SEM; data not shown) was similar among the dietary treatments. Broilers fed the 0.99% digestible Lys dose-response diet had greater (P ≤ 0.03) BW and BW gain and lower (P ≤ 0.001) feed conversion over the control-fed birds, but meat yield criteria were not different. Digestible Lys requirements were determined at 0.965, 1.012, 1.029, 0.963, 0.987, and 0.981%, respectively, for BW gain, feed conversion, carcass weight, carcass yield, total breast meat weight, and total breast meat weight yield using a quadratic broken-line model (Table 9).
Table 3. Analyzed amino acid composition of the experimental diets1 Experiment 1 Amino acid, % as fed Lys Met Cys Thr Ile Val Arg Trp Leu His Phe Ala Asp Glu Pro Ser Tyr 1Amino
Experiment 2
Low Lys
High Lys
Control
Low Lys
High Lys
Control
0.72 0.69 0.22 0.81 0.79 0.92 1.29 0.22 1.28 0.42 0.78 0.80 1.46 2.94 0.79 0.74 0.48
1.23 0.67 0.23 0.82 0.80 0.92 1.30 0.22 1.30 0.41 0.79 0.87 1.48 2.86 0.89 0.75 0.46
1.08 0.52 0.26 0.73 0.70 0.82 1.19 0.21 1.51 0.48 1.74 0.98 1.74 3.09 1.03 0.86 0.50
0.77 0.69 0.22 0.82 0.83 0.94 1.34 0.27 1.28 0.43 0.79 0.80 1.53 2.66 0.94 0.76 0.50
1.23 0.65 0.23 0.83 0.86 0.96 1.37 0.25 1.33 0.44 0.82 0.84 1.59 2.76 0.80 0.78 0.54
1.17 0.52 0.27 0.80 0.82 0.92 1.33 0.26 1.60 0.53 0.99 0.96 1.99 3.36 1.03 0.95 0.61
acid values were determined in duplicate (AOAC, 2006).
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Statistics. In both experiments, gradient treatment structure was conducted as a randomized complete block design. The 9 dose-response diets were represented with 9 and 12 replicate pens, respectively, in experiments 1 and 2. Six analyses were conducted using the following (SAS Institute, 2004): 1) PROC REG using linear response to explain potential digestible Lys effects; 2) PROC REG using quadratic response to explain potential digestible Lys effects; multiple coefficient determination values presented are based on proportion of the treatment effect that is explained by the response; 3) PROC MIXED using linear response to explain potential digestible Lys effects; 4) PROC MIXED using quadratic response to explain potential digestible Lys effects; lack of fit for this analysis is the treatment effect that is not being explained by the response (a measure of lack of fit as a component of variance was obtained from PROC MIXED); 5) an orthogonal contrast was conducted to compare the control diet (0.99% digestible Lys) versus the 0.99% digestible Lys doseresponse diet; and 6) a quadratic broken-line model was conducted using PROC NLIN based on Robbins et al. (2006). Digestible Lys requirement was estimated using quadratic broken-line methodology when a significant breakpoint was observed. Statistical significance was considered P ≤ 0.05 for dietary treatment differences.
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Table 4. Growth performance of Ross × Ross TP16 male broilers fed gradient levels of digestible Lys from 28 to 42 d of age, experiment 11 BW gain, kg
Feed intake, kg
Digestible Lys, % 0.64 0.71 0.78 0.85 0.92 0.99 1.06 1.13 1.20 Control (0.99%) SEM Source of variation
2.669 2.748 2.825 2.922 2.947 2.922 2.964 2.927 2.964 3.013 0.020
1.033 1.113 1.190 1.287 1.312 1.287 1.329 1.292 1.329 1.378 0.020
2.326 2.394 2.457 2.528 2.521 2.485 2.559 2.491 2.518 2.630 0.028
Linear trend Quadratic trend Control vs. 0.99%3 R2 CV, %
0.003 0.002 0.002 0.95 0.87
0.003 0.002 0.002 0.95 2.13
0.019 0.011 0.001 0.86 1.23
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Digestible Lys intake, mg/d 1,063 1,213 1,369 1,535 1,656 1,757 1,938 2,011 2,157 1,860 20 Probabilities 0.001 0.044 0.001 0.99 1.24
Digestible Lys intake:BW gain, mg:g
FCR,2 kg:kg
Mortality, %
14.40 15.29 16.10 16.73 17.69 19.13 20.46 21.80 22.75 18.91 0.20
2.222 2.199 2.036 1.977 1.924 1.918 1.862 1.924 1.895 1.928 0.033
0.8 0.7 0.8 0.7 0.7 0.7 2.2 0.0 0.7 1.5 0.9
0.002 0.003 0.84 0.95 1.66
0.94 0.68 0.54 0.04 76.82
0.001 0.009 0.44 0.99 1.18
1Values are least squares means of 9 replicate pens with 15 broilers per pen at 28 d of age. Grand BW mean at 28 d of age was 1.635 kg and 28-d BW was not significantly different among the treatments (P = 0.21). 2FCR = feed conversion ratio. 3Orthogonal contrast.
DISCUSSION
that extensive variability exists between batches of the same ingredient. Assays determining amino acid requirements should use test diets that are deficient in the amino acid under investigation and adequate in other amino acids. In the current research, the low-Lys diet with no added l-Lys was formulated to contain 0.64% digestible Lys. Amino acid analysis determined that the low-Lys diet had 0.71 and 0.77% total Lys, whereas total Lys for the highLys diets approximated 1.22 and 1.23% for experiments
Diets were formulated based on digestible coefficient ingredients of previously established values (Ajinomoto Heartland LLC, 2009), which were determined from an extensive number of assays. We elected to use digestible coefficients averaged across several assays rather than conducting digestible amino acid assays with feed ingredients or complete feeds due to the variation associated with this measurement. However, we do acknowledge
Table 5. Processing yields of Ross × Ross TP16 male broilers fed gradient levels of digestible Lys from 28 to 42 d of age, experiment 11 Chilled carcass 43-d BW, kg
Weight, kg
Yield, %
Digestible Lys, % 0.64 0.71 0.78 0.85 0.92 0.99 1.06 1.13 1.20 Control (0.99%) SEM Source of variation
2.798 2.876 2.949 3.065 3.060 2.981 3.074 3.036 3.080 3.099 0.037
1.978 2.052 2.127 2.196 2.023 2.169 2.203 2.183 2.229 2.235 0.029
70.7 71.4 72.1 71.6 72.0 72.8 71.7 71.9 72.4 72.1 0.3
Linear trend Quadratic trend Control vs. 0.99%2 R2 CV, %
0.008 0.046 0.027 0.77 1.57
0.005 0.015 0.11 0.89 1.44
Item
1Vaules
0.06 0.15 0.13 0.60 0.61
are least squares means of 9 replicate pens with 5 broilers at 43 d of age. contrast.
2Orthogonal
Abdominal fat Weight, kg 0.067 0.071 0.068 0.069 0.067 0.065 0.063 0.064 0.064 0.065 0.002 Probabilities 0.023 0.79 0.90 0.66 2.36
Total breast
Yield, %
Weight, kg
2.40 2.47 2.31 2.24 2.19 2.20 2.07 2.12 2.10 2.10 0.08
0.575 0.618 0.649 0.678 0.686 0.666 0.684 0.670 0.703 0.683 0.011
0.001 0.33 0.34 0.89 2.35
0.005 0.036 0.32 0.89 2.15
Yield, % 20.5 21.5 22.0 22.1 22.4 22.4 22.2 22.1 22.8 22.0 0.3 0.009 0.07 0.58 0.87 2.15
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BW, kg
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DIETARY LYSINE NEEDS OF BROILERS Table 6. Digestible Lys requirement of Ross × Ross TP16 based on quadratic broken-line model analyses, experiment 1 Response criteria
Estimated requirement1
95% CI
SEM
Probability value
Performance BW gain FCR2 Processing yields Carcass weight Carcass yield Breast weight
0.988 1.053 0.939 0.921 0.962
0.909 to 1.066 0.942 to 1.163 0.809 to 1.068 0.784 to 1.061 0.792 to 1.132
0.039 0.055 0.065 0.070 0.085
0.001 0.001 0.001 0.001 0.001
1The quadratic broken-line model is as follows: y = L + U × (R − x) × (R − x), where L is the ordinate, U is the slope of the line at values of x < R, R is the abscissa of the breakpoint, and the value R − is zero at values of x > R. 2FCR = feed conversion ratio.
was estimated at 0.994% when averaged across experiments for feed conversion, growth rate, and total breast meat weight. Han and Baker (1994) determined the digestible Lys requirement at 0.89 and 0.85% for feed conversion and BW gain, respectively, using brokenline analysis for 21- to 42-d-old male Ross broilers. Moreover, digestible Lys requirement for feed conversion was reported at 0.95 and 0.89%, respectively, for Ross and ISA male broilers from 20 to 40 d of age utilizing broken-line methodology (Mack et al., 1999). The higher digestible Lys requirement for the modern broiler compared with birds used in research from previous decades relates to less feed intake per unit of BW gain and a greater rate of meat accretion (Havenstein et al., 2003a,b; Dozier et al., 2008a, 2009a). In the present research, BW gain approximated 92 and 103 g/d for experiments 1 and 2, respectively. The accelerated growth rate of broilers used in the present research resulted in 10 to 12% higher digestible Lys requirements
Table 7. Growth performance of Cobb × Cobb 700 male broilers fed gradient additions of digestible Lys from 28 to 42 d of age, experiment 21
BW, kg
BW gain, kg
Feed intake, kg
Digestible Lys, % 0.64 0.71 0.78 0.85 0.92 0.99 1.06 1.13 1.20 Control (0.99%) SEM Source of variation
2.800 2.961 2.983 3.082 3.114 3.101 3.137 3.092 3.126 3.042 0.020
1.138 1.288 1.326 1.431 1.443 1.450 1.479 1.437 1.454 1.377 0.015
2.473 2.612 2.575 2.644 2.639 2.606 2.643 2.570 2.580 2.557 0.024
Linear response Quadratic response Control vs. 0.99%3 R2 CV, %
0.004 0.002 0.03 0.94 1.01
0.005 0.0007 0.001 0.96 1.84
0.37 0.017 0.16 0.67 1.36
Item
Digestible Lys intake, mg/d 1,130 1,324 1,434 1,605 1,734 1,843 2,001 2,074 2,211 1,808 17 Probabilities 0.0001 0.016 0.15 0.99 1.16
Digestible Lys intake:BW gain, mg:g 13.91 14.39 15.17 15.71 16.82 17.79 18.94 20.20 21.29 18.38 0.11 0.0001 0.0001 0.0003 0.99 0.64
FCR,2 kg:kg
Mortality, %
2.172 2.028 1.941 1.847 1.812 1.789 1.782 1.782 1.774 1.852 0.013
0.3 0.7 0.3 0.3 0.3 1.4 0.7 0.7 0.0 0.3 0.43
0.001 0.0001 0.001 0.98 0.96
0.91 0.28 0.07 0.19 75.37
1Values are least squares means of 12 replicate pens with 23 broilers per pen at 28 d of age. Grand BW mean at 28 d of age was 1.661 kg and 28-d BW was not significantly different among the treatments (P = 0.64). 2FCR = feed conversion ratio. 3Orthogonal contrast.
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1 and 2, respectively. The coefficient of determination for BW gain and feed conversion ranged from 0.94 to 0.98 in experiments 1 and 2, indicating that the lowLys diet was clearly deficient. The control-fed broilers had similar feed conversion and meat yield as birds fed the dose-response diet at 0.99% digestible Lys in experiment 1, and the dose-response diet formulated to 0.99% digestible Lys had better or similar growth performance and meat yield responses than control-fed birds in experiment 2. The good performance observed with the dose-response diets in both experiments provides evidence that digestible Lys requirements were not underestimated. Digestible Lys requirement varied from 0.921 to 1.053% and 0.965 to 1.029% for experiments 1 and 2, respectively, with the estimate being dependent upon the response criterion. Digestible Lys requirement was more pronounced for feed conversion than growth rate or breast meat accretion. Digestible Lys requirement
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Table 8. Processing weights and yields of Cobb × Cobb 700 male broilers fed gradient additions of digestible Lys from 28 to 42 d of age, experiment 21 Chilled carcass Yield,2 %
Digestible Lys, % 0.64 0.71 0.78 0.85 0.92 0.99 1.06 1.13 1.20 Control (0.99%) SEM Source of variation
2.099 2.144 2.236 2.264 2.300 2.300 2.339 2.267 2.335 2.263 0.020
71.2 71.6 71.6 72.5 72.5 72.7 73.1 72.6 72.7 72.9 0.35
Linear response Quadratic response Control vs. 0.99%3 R2 CV, %
0.003 0.014 0.21 0.91 1.26
0.002 0.018 0.81 0.90 0.30
Weight, kg
Yield, %
0.048 1.64 0.046 1.53 0.045 1.45 0.049 1.60 0.045 1.44 0.044 1.39 0.046 1.44 0.042 1.34 0.042 1.33 0.042 1.35 0.001 0.055 Probabilities 0.038 0.002 0.47 0.91 0.37 0.56 0.52 0.74 4.34 4.26
Total breast Weight, kg
Yield, %
0.618 0.656 0.697 0.731 0.752 0.742 0.763 0.730 0.756 0.737 0.009
21.0 21.9 22.3 23.4 23.7 23.4 23.8 23.4 23.5 23.7 0.22
0.004 0.002 0.70 0.94 1.92
0.006 0.001 0.39 0.95 1.06
1Values
are least squares means of 12 replicate pens with 5 broilers per pen processed at 43 d of age. are defined as grams of tissue per 100 g of live weight. 3Orthogonal contrast. 2Yields
when expressed as a percentage of the diet than birds used in previous research. The requirement for feed conversion was approximately 6% higher than for BW gain and total breast meat weight when averaged across both experiments in the research reported herein. Other research has also found higher Lys requirements for feed conversion than BW gain (Han and Baker, 1994; Leclercq, 1998; Baker et al., 2002; Dozier et al., 2008a, 2009a). As digestible Lys exceeds the concentration for the requirement of BW gain, feed intake decreases without a change in BW gain, translating to a higher requirement for feed conversion (Baker et al., 2002). Digestible Lys requirements for feed conversion were determined at 1.05 and 1.01% in experiments 1 and 2, respectively. Feed conversion of broilers fed at optimum digestible Lys requirement differed between the 2 experiments, with broilers in experiment 2 having 0.073 lower feed conversion (1.789 vs. 1.862) than birds in experiment 1. Moreover, broilers in experiment 2 were 163 g heavier and consumed 121 g more feed than birds in experiment 1. The accelerated growth rate exhibited by broilers in experiment 2 may have translated to a lower feed conversion than birds in experiment 1. A direct comparison between experiments is precluded due to differences in experimental facilities, season, genetic strain, pellet quality, feed ingredients, lighting schedule, and management. Postnatal muscle accretion is influenced by an increase in protein synthesis or decreased protein degradation, or both. Insulin-like growth-factor I increases protein synthesis and decreases protein degradation of muscle cells (Vandenburgh et al., 1991). Broilers fed diets varying in dietary CP have been shown to regu-
late IGF-I (Farhat and Chaver, 1999; Tesseraud et al., 2003). Rosebrough et al. (1996) reported a 56% increase in IGF-I plasma concentrations with broilers fed diets formulated to 21.0 versus 12.0% CP. In the current research, it was shown that broilers fed deficient dietary Lys concentrations did not exhibit altered plasma IGFI concentrations. Based on this finding, we chose not to evaluate this measurement in experiment 2. Dietary amino acid requirements for broiler chickens are typically based on growth performance and meat yield measurements. In swine, response criteria for determining amino requirements may include growth performance, carcass yield, and plasma urea nitrogen mea-
Figure 1. Effects of digestible Lys on plasma uric acid concentration (experiment 2). Means are represented by 6 replicates (2 birds per replicate). Error bars denote SEM.
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Weight, kg
Item
Abdominal fat
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DIETARY LYSINE NEEDS OF BROILERS Table 9. Digestible Lys requirement of Cobb × Cobb 700 based on quadratic broken-line model analyses, experiment 2 Response criteria
Estimated requirement1
95% CI
SEM
Probability value
Performance BW gain FCR2 Processing yields Carcass weight Carcass yield Breast weight Breast yield
0.965 1.012 1.029 0.963 0.987 0.981
0.903 to 1.026 0.969 to 1.055 0.900 to 1.158 0.808 to 1.118 0.906 to 1.068 0.885 to 1.076
0.031 0.021 0.065 0.070 0.040 0.048
0.001 0.001 0.001 0.001 0.001 0.001
1The quadratic broken-line model is as follows: y = L + U × (R − x) × (R − x), where L is the ordinate, U is the slope of the line at values of x < R, R is the abscissa of the breakpoint, and the value R − is zero at values of x > R. 2FCR = feed conversion ratio.
experiment 2 than experiment 1. Broilers fed the doseresponse diet consuming 0.99% digestible Lys consumed 1,843 mg/d of digestible Lys in experiment 2, whereas digestible Lys intake approximated 1,757 mg/d when broilers were fed a diet containing 0.99% digestible Lys in experiment 1. Overall average requirements based on BW gain, feed conversion, and breast meat yield were 1.001 and 0.986%, respectively, for experiments 1 and 2. It is important to note that these requirements were averaged across 2 broiler strains. These data support a higher digestible Lys requirement (0.99%) of male broilers from 28 to 42 d of age on a percentage basis than previous research (Han and Baker, 1994; Leclercq, 1998; Mack et al., 1999) as noted by less feed intake per unit of BW gain and a greater meat accretion rate. Digestible Lys requirements (percentage basis) were in close agreement between strains, indicating that these 2 genetic sources had similar Lys needs to optimize growth and meat yield.
REFERENCES Ajinomoto Heartland LLC. 2009. True Digestibility of Essential Amino Acids for Poultry. Ajinomoto Heartland LLC, Chicago, IL. AOAC. 2006. Official Methods of Analysis. 18th ed. Association of Official Analytical Chemists, Arlington, VA. Baker, D. H., A. B. Batal, T. M. Parr, N. R. Augspurger, and C. M. Parsons. 2002. Ideal ratio (relative to lysine) of tryptophan, threonine, isoleucine, and valine for chicks during the second and third posthatch. Poult. Sci. 81:485–494. Corzo, A., W. A. Dozier III, and M. T. Kidd. 2006. Dietary lysine needs of late-developing heavy broilers. Poult. Sci. 85:457–461. Corzo, A., W. A. Dozier III, R. E. Loar, M. T. Kidd, and P. B. Tillman. 2009. Assessing the threonine-to-lysine ratio of female broilers from 14 to 28 days of age. J. Appl. Poult. Res. 18:237– 243. Corzo, A., E. T. Moran Jr., and D. Hoehler. 2002. Lysine need of heavy broiler males applying the ideal protein concept. Poult. Sci. 81:1863–1868. Corzo, A., E. T. Moran Jr., and D. Hoehler. 2003. Lysine needs of summer-reared male broilers from six to eight weeks of age. Poult. Sci. 82:1602–1607. Donsbough, A. L., S. Powell, A. Waguespack, T. D. Bidner, and L. L. Southern. 2010. Uric acid, urea, and ammonia concentrations in serum and uric acid concentration in excreta as indicators of amino acid utilization in diets for broilers. Poult. Sci. 89:287–294.
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surements. Because uric acid is the main end product in nitrogen metabolism for poultry, plasma uric acid may be a more sensitive measurement for determining amino acid requirements than plasma urea nitrogen. In experiment 2, significant quadratic responses of plasma urea nitrogen and plasma uric acid were not observed for digestible Lys; hence, requirements were not determined. In agreement with the present research, plasma urea concentration was not altered when broilers were fed increasing dietary Lys concentrations (Corzo et al., 2003). Dozier et al. (2009b) reported a decreasing linear response of plasma urea nitrogen with progressive additions of digestible Lys, but a quadratic response was not obtained; therefore, a requirement could not be estimated. In contrast, Donsbough et al. (2010) have reported that serum uric acid, serum urea nitrogen, and excreta uric acid concentrations are indicators of amino acid utilization for broilers. These authors suggested a fasting and refeeding schedule to obtain the most consistent results with blood collection occurring at 2 h refeeding. In the research reported herein and Dozier et al. (2009b), blood was collected with broilers fed ad libitum. Dietary Lys alters carcass composition of broilers (Han and Baker, 1994; Leclercq, 1998; Mack et al., 1999; Corzo et al., 2002, 2006; Dozier et al., 2008a). Lipid accretion rate is decreased by gradient increases of dietary Lys (Han and Baker, 1994; Leclercq, 1998; Mack et al., 1999). Broilers fed diets containing 1.18% total Lys had the lowest abdominal fat percentage, whereas optimum BW gain and feed conversion responses were obtained with 0.92 and 1.01% total dietary Lys (Leclercq, 1998). Significant linear responses were observed for abdominal fat percentage in experiments 1 and 2. Variation was more pronounced with abdominal fat percentage than other response criteria in experiment 2, which may have led to the inability to detect a significant quadratic response. Conversely, abdominal fat percentage was similar with broilers fed progressive concentrations of dietary Lys (Corzo et al., 2006; Dozier et al., 2008a). Digestible Lys intake needed to optimize growth performance and meat yield for male broilers was higher in
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Dozier et al. Lemme, A., V. Ravindran, and W. L. Bryden. 2004. Standardized ileal amino acid digestibility of raw materials in broilers. Proceedings of the Multi-State Poultry Feeding and Nutrition and Health and Management Conference and Degussa Corporation’s Technical Symposium, Indianapolis, IN. CD-ROM. Mack, S., D. Bercovici, G. De Groote, B. Leclercq, M. Lippens, M. Pack, J. B. Schutte, and S. Van Cauwenberghe. 1999. Ideal amino acid profile and dietary lysine specification for broiler chickens of 20 to 40 days of age. Br. Poult. Sci. 40:257–265. McMurtry, J. P., G. L. Francis, F. Z. Upton, G. Rosselot, and D. M. Brocht. 1994. Developmental changes in chicken and turkey insulin-like growth factor-I (IGF-I) studies with a homologous radioimmunoassay for chicken IGF-I. J. Endocrinol. 142:225–234. NRC. 1994. Nutrient Requirements of Poultry. 9th rev. ed. National Academy Press, Washington, DC. Robbins, K. R., A. M. Sexton, and L. L. Southern. 2006. Estimation of nutrient requirements using broken-line regression analysis. J. Anim. Sci. 84(E. Suppl.):E155–E165. Rosebrough, R. W., A. D. Mitchell, and P. J. McMurtry. 1996. Dietary crude protein changes rapidly alter metabolism and plasma insulin-like growth factor I concentrations in broiler chickens. J. Nutr. 126:2888–2898. SAS Institute. 2004. SAS User’s Guide: Statistics. Version 9.1 ed. SAS Institute Inc., Cary, NC. Simmons, J. D., B. D. Lott, and D. M. Miles. 2003. The effects of high air velocity on broiler performance. Poult. Sci. 82:232– 234. Sklan, D., and Y. Noy. 2003. Crude protein and essential amino acid requirements in chicks during the first week posthatch. Br. Poult. Sci. 44:266–274. Talke, H., and G. E. Schubert. 1965. Enzymatic urea determination in the blood and serum in the Warburg optical test. Klin. Wochenschr. 43:174–175. Tesseraud, S., R. A. E. Pym, E. Le Bihon-Duval, and M. J. Duculos. 2003. Response of broilers selected on carcass quality to dietary protein supply: Live performance, muscle development, and circulating insulin-like growth factor (IGF-I and -II). Poult. Sci. 82:1011–1016. Town, M. H., S. Gehm, B. Hammer, and J. Ziegenhorn. 1985. A sensitive colorimetric method for the enzymatic determination of uric acid. J. Clin. Chem. Clin. Biochem. 23:591–599. Vandenburgh, H. H., P. Karlish, J. Shansky, and R. Feldstein. 1991. Insulin and IGF-1 induce pronounced hypertrophy of skeletal myofibers in tissue culture. Am. J. Physiol. 260:C475–C484.
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Dozier, W. A., III, A. Corzo, M. T. Kidd, and M. W. Schilling. 2008a. Dietary digestible lysine requirements of male and female broilers from forty-nine to sixty-three days of age. Poult. Sci. 87:1385–1391. Dozier, W. A., III, A. Corzo, M. T. Kidd, P. B. Tillman, and S. L. Branton. 2009a. Digestible lysine requirements of male and female broilers from fourteen to twenty-eight days of age. Poult. Sci. 88:1676–1682. Dozier, W. A., III, A. Corzo, M. T. Kidd, P. B. Tillman, J. L. Purswell, and B. J. Kerr. 2009b. Dietary lysine responses of male broilers from fourteen to twenty-eight days of age subjected to different environmental conditions. J. Appl. Poult. Res. 18:690– 698. Dozier, W. A., III, M. T. Kidd, and A. Corzo. 2008b. Dietary amino acid responses of broiler chickens. J. Appl. Poult. Res. 17:157– 167. Farhat, A., and E. R. Chaver. 1999. Effects of line, dietary protein, sex, age, and feed withdrawal on insulin-like growth factor-I concentrations in broiler chickens. Poult. Sci. 78:1307–1312. Garcia, A., and A. B. Batal. 2005. Changes in the digestible lysine and sulfur amino acid needs of broiler chicks during the first three weeks posthatching. Poult. Sci. 84:1350–1355. Han, Y., and D. H. Baker. 1991. Lysine requirements of fast- and slow-growing broiler chicks. Poult. Sci. 70:2108–2114. Han, Y., and D. H. Baker. 1994. Digestible lysine requirement of male and female broiler chicks during the period three to six weeks posthatching. Poult. Sci. 73:1739–1745. Havenstein, G. B., P. R. Ferket, and M. A. Qureshi. 2003a. Growth, livability, and feed conversion of 1957 versus 2001 broilers when fed representative 1957 and 2001 broiler diets. Poult. Sci. 82:1500–1508. Havenstein, G. B., P. R. Ferket, and M. A. Qureshi. 2003b. Carcass composition and yield of 1957 versus 2001 broilers when fed representative 1957 and 2001 broiler diets. Poult. Sci. 82:1509– 1518. Kidd, M. T., C. D. McDaniel, S. L. Branton, E. R. Miller, B. B. Boren, and B. I. Fancher. 2004. Increasing amino acid density improves live performance and carcass yields of commercial broilers. J. Appl. Poult. Res. 13:593–604. Knowles, T. A., and L. L. Southern. 1998. The lysine requirement and ratio of total sulfur amino acids to lysine for chicks fed adequate or inadequate lysine. Poult. Sci. 77:564–569. Labadan, M. C., K. N. Hsu, and R. E. Austic. 2001. Lysine and arginine requirements of broiler chickens at two- to three-week intervals to eight weeks of age. Poult. Sci. 80:599–606. Leclercq, B. 1998. Specific effects of lysine on broiler production: Comparison with threonine and valine. Poult. Sci. 77:118–123.
Key words: broiler, lysine, live performance, carcass part, physiological variable 2010 Poultry Science 89:2173–2182 doi:10.3382/ps.2010-00710
INTRODUCTION Lysine is typically the second-limiting amino acid for broiler chickens. Defining the optimum Lys requirement is economically important because feeding diets either deficient or in excess of Lys need can translate to poor performance or increased diet cost. Today’s highperforming broiler consumes less feed per unit of BW gain than birds of previous decades (Havenstein et al., 2003a,b; Dozier et al., 2008a,b). The modern broiler responds to higher dietary amino acid levels than the commercial broiler used in previous decades due to improvements in genetic selection, such as decreased feed intake per unit of BW gain and greater accretion rate ©2010 Poultry Science Association Inc. Received February 16, 2010. Accepted June 27, 2010. 1 Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by Auburn University, Mississippi State University, or the USDA. 2 Corresponding author: [email protected]
for meat yield (Kidd et al., 2004; Dozier et al., 2008b, 2009a; Corzo et al., 2009). Dozier et al. (2009a) reported that the digestible Lys requirement for male broilers from 14 to 28 d of age was 18% higher than the NRC (1994) recommendations. Moreover, these authors determined a 162% increase in 14- to 28-d BW gain than that reported by NRC (1994). The increased BW gain of the modern broiler suggests higher amino acid needs compared with birds used in previous research. Dietary Lys requirement has been evaluated more extensively in the starter (Han and Baker, 1991; Knowles and Southern, 1998; Labadan et al., 2001; Baker et al., 2002; Sklan and Noy, 2003; Garcia and Batal, 2005) and less extensively in the grower (Labadan et al., 2001; Dozier et al., 2009a), finisher (Han and Baker, 1994; Leclercq, 1998; Mack et al.,1999), and withdrawal (Corzo et al., 2002, 2006; Dozier et al., 2008a) periods. Dietary Lys requirement is dependent upon the response criteria, with requirements often being the highest for feed conversion (Han and Baker, 1994; Leclercq, 1998; Mack et al., 1999; Baker et al., 2002; Corzo et
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ABSTRACT Research addressing digestible Lys requirement data of modern broilers from 4 to 6 wk of age is limited. Male broilers (1,632 Ross × Ross TP16 and 3,000 Cobb × Cobb 700) were used in separate experiments to determine the digestible Lys requirements from 28 to 42 d. In each experiment, 2 diets (dilution and summit) consisting of corn, soybean meal, animal protein meal, and peanut meal were formulated to be adequate in all other amino acids. The dilution and summit diets were blended to create 9 titration diets. A control diet formulated to contain corn, soybean meal, and animal protein meal as the primary ingredients was used for comparison with the titration diets. Body weight gain, feed intake, digestible Lys intake, digestible Lys intake:BW gain, feed conversion, mortality, carcass yields, and physiological measurements were assessed during experimentation. Digestible Lys requirements
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MATERIALS AND METHODS Dietary Treatments Ten experimental diets were fed from 28 to 42 d of age consisting of 9 graded concentrations of digestible Lys plus a positive control. Two diets consisting of corn, soybean meal, animal protein meal, and peanut meal were formulated to meet or exceed NRC (1994) nutrient requirements (Tables 1 and 2). Diets were formulated based on amino acid ratios to ensure adequacy of essential amino acids so the digestible Lys response would not be limited. The 2 diets were mixed in varying proportions to create 9 dose-response diets ranging from 0.64 to 1.20% digestible Lys in 0.07% increments. Diet dilution technique was used as the high-Lys diet was formulated to contain 0.71% of l-Lys·HCl and the low-Lys diet contained no added l-Lys·HCl. Treatment differences were not due solely to digestible Lys percentage from added l-Lys-HCl because the amount of corn, soybean meal, poultry oil, Gly, and l-Glu differed between the low-Lys and the high-Lys diets in experiment 1 (Table 1). In experiment 2, the diets differed in the content of ground corn and Gly (Table 2). The control diet was formulated to contain 0.99% digestible Lys and was used to validate the dose-response diet (0.99% digestible Lys level). Corn, soybean meal, animal protein meals, and peanut meal were analyzed for total amino acids (methods 985.28 and 994.12; AOAC, 2006) and CP (method 968.06; AOAC, 2006) composi-
tion before diet formulation. Digestible amino acid values were determined from digestible coefficients (Ajinomoto Heartland LLC, 2009) and analyzed total amino acid content of the ingredients. Digestible TSAA, Thr, Val, Ile, Arg, and Trp ratios to Lys were formulated based on a modification of digestible ratios reported by Lemme et al. (2004), with the ratios being increased by 2 percentage points to ensure that these essential amino acids were not limiting. Digestibility coefficients for ingredients were subtracted by 0.5 of the SD to add a margin of safety. Digestibility coefficients for corn, soybean meal, meat and bone meal, peanut meal, and poultry by-product meal were based on 45, 85, 124, 7, and 57 sample assays, respectively. Diets were manufactured as pellets. Representative samples were obtained to validate the dietary Lys concentrations of the experimental diets (Table 3).
Experiments 1 and 2 All procedures relating to the use of live birds were approved by the USDA-Agricultural Research Service Animal Care and Use Committee at the Mississippi State location and Auburn University Institutional Animal Care and Use Committee. Ross × Ross TP16 and Cobb × Cobb 700 male broiler chicks (experiment 1 = 1,632; experiment 2 = 3,000) were obtained from a primary breeder hatchery and were vaccinated for Marek’s disease, Newcastle disease, and infectious bronchitis. Experiments were conducted at the USDA-Agricultural Research Service Poultry Research Unit at Mississippi State (Ross × Ross TP16 strain) and at Auburn University (Cobb × Cobb 700 strain); hence, location and strain differences make comparison between studies difficult. Chicks were reared in a solid-side wall facility and were fed common diets until 28 d of age (starter = digestible TSAA, 0.92%; digestible Lys, 1.22%; digestible Thr, 0.83%; CP, 23.0%; AMEn, 3,075 kcal/ kg; grower = digestible TSAA, 0.86%; digestible Lys, 1.13%; digestible Thr, 0.74%; CP, 20.9%; AMEn, 3,140 kcal/kg). At 28 d of age, chicks were equalized among floor pens (0.09 m2/bird; experiment 1 = 15 birds/pen; experiment 2 = 23 birds/pen). Each pen was equipped with a hanging feeder, a nipple drinker line, and used litter. Birds consumed feed and water on an ad libitum basis and experimental diets were provided in whole pellet form. Ambient temperature set points consisted of 33°C at placement until 4 d of age, 32°C from 5 to 9 d of age, 29°C from 10 to 14 d of age, 27°C from 15 to 23 d of age, 25°C from 24 to 28 d of age, 23°C from 29 to 33 d of age, 21°C from 34 to 38 d of age, and 19°C from 39 to 42 d of age. Actual average ambient temperatures during experimentation were 23.6°C ± 1.2 SD for experiment 1 and 23.1°C ± 3.0 SD for experiment 2. Photoperiod was a continuous schedule with lighting intensities of 30 lx from 0 to 7 d of age, 10 lx from 8 to 12 d of age, and 3 lx from 23 to 28 d of age for Ross × Ross TP16 male broilers in experiment 1 and the lighting schedule for experiment 2 consisted of a 23L:1D
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al., 2006; Dozier et al., 2008a, 2009a). Leclercq (1998) reported the total Lys requirements at 0.92, 0.97, and 1.01%, respectively, for BW gain, breast meat yield, and feed conversion for 20- to 40-d-old male broilers. Han and Baker (1994) determined the digestible Lys requirement for 21- to 42-d-old male broilers at 0.89% for feed conversion; however, a requirement for BW gain was estimated to be 0.85%. In addition, Mack et al. (1999) estimated dietary Lys requirements of Ross and ISA broilers from 20 to 40 d of age at 0.95 and 0.89%, respectively, using feed conversion as the response criterion. In commercial practice, market weights and anticoccidial programs often dictate feeding schedules. Daily growth rate typically reaches a maximum from 4 to 6 wk of age during the life cycle of the broiler (Simmons et al., 2003), and this age interval coincides with finishing periods. In addition, approximately 43% of the broilers marketed in the US industry are 2.9 kg or greater. Research determining the digestible Lys requirement in modern broilers from 1.5 to 3.0 kg of BW is sparse. Research reported herein evaluated digestible Lys requirements of Ross × Ross TP16 and Cobb × Cobb 700 male broilers. Measurements encompassed live performance, yields of carcass parts, and physiological variables such as plasma insulin-like growth factor I (IGF-I), blood urea nitrogen, and uric acid concentrations.
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DIETARY LYSINE NEEDS OF BROILERS Table 1. Ingredient and calculated composition of diets provided during a 28- to 42-d production period, experiment 1 Low Lys
High Lys
Control
Ingredient, % as fed Ground corn Soybean meal (48% CP) Peanut meal (41% CP) Poultry by-product meal Poultry oil Dicalcium phosphate Calcium carbonate Sodium chloride Sodium bicarbonate dl-Met l-Lys·HCl l-Thr l-Val l-Ile l-Arg l-Trp Gly l-Glu Choline chloride Vitamin and mineral premix1 Coccidiostat2 Calculated analysis AMEn, kcal/kg CP, % Digestible TSAA, % Digestible Lys, % Digestible Thr, % Digestible Ile, % Digestible Val, % Digestible Trp, % Digestible Arg, % Digestible TSAA:Lys ratio Digestible Thr:Lys ratio Digestible Val:Lys ratio Digestible Ile:Lys ratio Digestible Arg:Lys ratio Digestible Trp:Lys ratio Ca, % Nonphytate P, % Na, %
70.30 11.91 7.50 2.69 2.40 1.33 0.90 0.13 0.40 0.46 — 0.31 0.25 0.25 0.20 0.07 0.33 0.33 0.06 0.13 0.05 3,186 17.75 0.92 0.64 0.81 0.81 0.92 0.20 1.25 144 127 144 127 196 32 0.84 0.42 0.23
69.80 12.16 7.50 2.69 2.22 1.33 0.90 0.13 0.40 0.46 0.71 0.31 0.25 0.25 0.20 0.07 0.19 0.19 0.06 0.13 0.05 3,186 18.25 0.92 1.20 0.81 0.81 0.92 0.20 1.25 77 68 77 68 105 17 0.84 0.42 0.23
69.51 20.80 — 4.00 2.47 1.11 0.84 0.32 0.25 0.23 0.17 0.06 — — — — — 0.06 0.13 0.05 3,186 18.20 0.77 0.99 0.67 0.67 0.77 0.17 1.10 78 68 78 68 111 17 0.84 0.42 0.22
1Vitamin and mineral premix included the following per kilogram of diet: vitamin A (vitamin A acetate), 4,960 IU; vitamin D (cholecalciferol), 1,653 IU; vitamin E (dl-α-tocopherol acetate), 27 IU; menadione (menadione sodium bisulfate complex), 0.99 mg; vitamin B12 (cyanocobalamin), 0.015 mg; folic (folic acid), 0.8 mg; d-pantothenic acid (calcium pantothenate), 15 mg; riboflavin (riboflavin), 5.4 mg; niacin (niacinamide), 45 mg; thiamin (thiamin mononitrate), 2.7 mg; d-biotin (biotin), 0.07 mg; pyridoxine (pyridoxine hydrochloride), 5.3 mg, Mn (manganous oxide), 90 mg; Zn (zinc oxide), 83 mg; Fe (iron sulfate monohydrate), 121 mg; Cu (copper sulfate pentahydrate), 12 mg; I (calcium iodate), 0.5 mg; and Se (sodium selenite), 0.3 mg. 2BioCox 60 provided 60 g/907 kg of salinomycin from Alpharma (Fort Lee, NJ).
photoperiod with an intensity of 30 lx from 0 to 7 d of age, 18L:6D photoperiod with an intensity of 10 lx from 8 to 12 d of age, 15L:9D photoperiod with an intensity of 5 lx from 13 to 28 d of age, 18L:6D photoperiod with an intensity of 2.5 lx from 29 to 39 d of age, and 23L:1D photoperiod with an intensity of 2.5 lx from 40 to 42 d of age for Cobb × Cobb 700 male broilers in experiment 2. Light intensity settings were verified at bird level (30 cm) using a photometric sensor with National Institute of Standards and Technology-traceable calibration (403125, Extech Instruments, Waltham, MA) for each intensity adjustment. Birds and feed were weighed on d 28 and 42 for the determination of BW gain, feed intake, digestible Lys intake, digestible intake:BW gain, and feed conversion. Mortality was recorded daily.
On d 43, five birds per pen were randomly selected for processing, weighed, placed in coops, and transported to a pilot poultry processing plant (experiment 1 = Mississippi State University; experiment 2 = Auburn University). Feed was removed 12 h before processing. Birds were electrically stunned, bled, scalded, picked, and mechanically eviscerated. Whole carcass (without abdominal fat) and abdominal fat were weighed. Carcasses were split into front and back halves and placed on ice for 18 h. Afterward, the front halves were deboned to obtain weights of pectoralis major and minor muscles. Carcass, abdominal fat, and total breast meat (pectoralis major and minor muscles) yields were expressed as a percentage of 43-d BW of selected broilers.
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Blood Analysis Experiment 1. On d 39, blood was collected via the ulnar vein [heparinized (4.5 mL; 50 IU/mL−1) monovette syringe equipped with a 20-gauge needle that was 25.4 mm in length] from 2 birds per pen of 7 replicates from broilers fed dose-response diets formulated to 0.64, 0.99, and 1.20% digestible Lys directly into tubes containing EDTA. Plasma concentrations of IGF-I were determined using RIA as described by McMurtry et al. (1994). Samples were analyzed in a single assay to avoid interassay variation and the CV was 3.9%.
Experiment 2. Plasma urea nitrogen and uric acid were measured in this experiment as response criteria for determining the digestible Lys requirement. On d 44, blood was collected from 2 birds from 6 replicate pens of birds receiving the 10 dietary treatments via the ulnar vein directly into a heparinized (50 IU/mL−1) monovette syringe. Samples from each bird were centrifuged at 2,000 × g for 5 min and 1 mL of plasma was obtained and stored at −20°C for later analysis. Plasma concentrations of blood urea nitrogen (Talke and Schubert, 1965) and uric acid (Town et al., 1985) were determined using an auto chemistry analyzer (Hitachi 911, Roche Diagnostics, Indianapolis, IN).
Table 2. Ingredient and calculated composition of diets provided during a 28- to 42-d production period, experiment 2 Low Lys
High Lys
Control
Ingredient, % as fed Ground corn Soybean meal (48% CP) Peanut meal (41% CP) Meat and bone meal Poultry oil Defluorinated phosphate Calcium carbonate Sodium chloride Sodium bicarbonate dl-Met l-Lys·HCl l-Thr l-Val l-Ile l-Arg l-Trp Gly Mineral premix1 Vitamin premix2 Phytase3 Coccidiostat4 Calculated analysis AMEn, kcal/kg CP, % Digestible TSAA, % Digestible Lys, % Digestible Thr, % Digestible Ile, % Digestible Val, % Digestible Trp, % Digestible Arg, % Digestible TSAA:Lys ratio Digestible Thr:Lys ratio Digestible Val:Lys ratio Digestible Ile:Lys ratio Digestible Arg:Lys ratio Digestible Trp:Lys ratio Ca, % Nonphytate P, % Na, %
67.51 15.39 7.50 3.00 1.65 0.33 1.15 0.10 0.48 0.52 — 0.34 0.29 0.30 0.22 0.08 0.57 0.25 0.25 0.02 0.05 3,125 18.65 0.92 0.64 0.80 0.83 0.92 0.22 1.28 144 125 144 129 199 33 0.88 0.44 0.22
67.36 15.39 7.50 3.00 1.65 0.33 1.15 0.10 0.48 0.52 0.72 0.34 0.29 0.30 0.22 0.08 — 0.25 0.25 0.02 0.05 3,125 18.65 0.92 1.20 0.80 0.83 0.92 0.22 1.28 77 67 77 69 107 18 0.88 0.44 0.22
62.79 28.23 — 3.00 2.91 0.27 1.15 0.33 0.30 0.27 0.12 0.06 — — — — — 0.25 0.25 0.02 0.05 3,125 19.55 0.76 0.99 0.66 0.68 0.79 0.19 1.16 77 67 77 69 107 18 0.88 0.44 0.22
1Mineral premix included the following per kilogram of diet: Mn (manganous oxide), 65 mg; Zn (zinc oxide), 55 mg; Fe (iron sulfate monohydrate), 55 mg; Cu (copper sulfate pentahydrate), 6 mg; I (calcium iodate), 1 mg; and Se (sodium selenite), 0.3 mg. 2Vitamin premix included the following per kilogram of diet: vitamin A (vitamin A acetate), 8,000 IU; vitamin D (cholecalciferol), 2,000 IU; vitamin E (dl-α-tocopherol acetate), 8 IU; menadione (menadione sodium bisulfate complex), 2 mg; vitamin B12 (cyanocobalamin), 0.02 mg; folic (folic acid), 0.5 mg: d-pantothenic acid (calcium pantothenate), 15 mg; riboflavin (riboflavin), 5.4 mg; niacin (niacinamide), 45 mg; thiamin (thiamin mononitrate), 1 mg; d-biotin (biotin), 0.05 mg; pyridoxine (pyridoxine hydrochloride), 2.2 mg; and choline (choline chloride), 500 mg. 3Quantum Phytase from AB Vista (Marlborough, Wiltshire, UK). 4BioCox 60 provided 60 g/907 kg of salinomycin from Alpharma (Fort Lee, NJ).
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RESULTS Experiment 1 Ross × Ross TP16 male broilers fed gradient concentrations of digestible Lys displayed significant (P ≤ 0.05) quadratic responses for BW, BW gain, feed intake, Lys intake, Lys intake:BW gain, feed conversion, carcass weight, and total breast meat weight (Tables 4 and 5). Linear responses (P ≤ 0.03) were observed for
abdominal fat weight, abdominal fat percentage, and breast meat yield. Plasma IGF-I concentrations (grand mean = 38.49 µmol/L ± 1.78 SEM; data not shown) were not different (P > 0.05) from broilers fed diets formulated to contain 0.64, 0.99, or 1.20% digestible Lys. Control-fed broilers grew faster (P ≤ 0.002) and consumed more feed (P ≤ 0.001) than broilers fed the dose-response diet formulated to 0.99% digestible Lys, but other variables measured were similar (P > 0.05). Digestible Lys requirements were estimated at 0.988, 1.053, 0.939, 0.921, and 0.962%, respectively, for BW gain, feed conversion, carcass weight, carcass yield, and total breast weight based on quadratic broken-line methodology (Table 6).
Experiment 2 Feeding Cobb × Cobb 700 male broilers progressive concentrations of digestible Lys resulted in quadratic responses (P ≤ 0.02) in BW, BW gain, feed intake, Lys intake, Lys intake:BW gain, feed conversion, carcass weight, carcass yield, total breast meat, and total breast meat yield, and linear responses (P ≤ 0.04) were observed for abdominal fat weight, abdominal fat percentage, and plasma uric acid concentration (Tables 7 and 8; Figure 1). Plasma nitrogen (grand mean = 2.44 mg/dL ± 0.18 SEM; data not shown) was similar among the dietary treatments. Broilers fed the 0.99% digestible Lys dose-response diet had greater (P ≤ 0.03) BW and BW gain and lower (P ≤ 0.001) feed conversion over the control-fed birds, but meat yield criteria were not different. Digestible Lys requirements were determined at 0.965, 1.012, 1.029, 0.963, 0.987, and 0.981%, respectively, for BW gain, feed conversion, carcass weight, carcass yield, total breast meat weight, and total breast meat weight yield using a quadratic broken-line model (Table 9).
Table 3. Analyzed amino acid composition of the experimental diets1 Experiment 1 Amino acid, % as fed Lys Met Cys Thr Ile Val Arg Trp Leu His Phe Ala Asp Glu Pro Ser Tyr 1Amino
Experiment 2
Low Lys
High Lys
Control
Low Lys
High Lys
Control
0.72 0.69 0.22 0.81 0.79 0.92 1.29 0.22 1.28 0.42 0.78 0.80 1.46 2.94 0.79 0.74 0.48
1.23 0.67 0.23 0.82 0.80 0.92 1.30 0.22 1.30 0.41 0.79 0.87 1.48 2.86 0.89 0.75 0.46
1.08 0.52 0.26 0.73 0.70 0.82 1.19 0.21 1.51 0.48 1.74 0.98 1.74 3.09 1.03 0.86 0.50
0.77 0.69 0.22 0.82 0.83 0.94 1.34 0.27 1.28 0.43 0.79 0.80 1.53 2.66 0.94 0.76 0.50
1.23 0.65 0.23 0.83 0.86 0.96 1.37 0.25 1.33 0.44 0.82 0.84 1.59 2.76 0.80 0.78 0.54
1.17 0.52 0.27 0.80 0.82 0.92 1.33 0.26 1.60 0.53 0.99 0.96 1.99 3.36 1.03 0.95 0.61
acid values were determined in duplicate (AOAC, 2006).
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Statistics. In both experiments, gradient treatment structure was conducted as a randomized complete block design. The 9 dose-response diets were represented with 9 and 12 replicate pens, respectively, in experiments 1 and 2. Six analyses were conducted using the following (SAS Institute, 2004): 1) PROC REG using linear response to explain potential digestible Lys effects; 2) PROC REG using quadratic response to explain potential digestible Lys effects; multiple coefficient determination values presented are based on proportion of the treatment effect that is explained by the response; 3) PROC MIXED using linear response to explain potential digestible Lys effects; 4) PROC MIXED using quadratic response to explain potential digestible Lys effects; lack of fit for this analysis is the treatment effect that is not being explained by the response (a measure of lack of fit as a component of variance was obtained from PROC MIXED); 5) an orthogonal contrast was conducted to compare the control diet (0.99% digestible Lys) versus the 0.99% digestible Lys doseresponse diet; and 6) a quadratic broken-line model was conducted using PROC NLIN based on Robbins et al. (2006). Digestible Lys requirement was estimated using quadratic broken-line methodology when a significant breakpoint was observed. Statistical significance was considered P ≤ 0.05 for dietary treatment differences.
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Table 4. Growth performance of Ross × Ross TP16 male broilers fed gradient levels of digestible Lys from 28 to 42 d of age, experiment 11 BW gain, kg
Feed intake, kg
Digestible Lys, % 0.64 0.71 0.78 0.85 0.92 0.99 1.06 1.13 1.20 Control (0.99%) SEM Source of variation
2.669 2.748 2.825 2.922 2.947 2.922 2.964 2.927 2.964 3.013 0.020
1.033 1.113 1.190 1.287 1.312 1.287 1.329 1.292 1.329 1.378 0.020
2.326 2.394 2.457 2.528 2.521 2.485 2.559 2.491 2.518 2.630 0.028
Linear trend Quadratic trend Control vs. 0.99%3 R2 CV, %
0.003 0.002 0.002 0.95 0.87
0.003 0.002 0.002 0.95 2.13
0.019 0.011 0.001 0.86 1.23
Item
Digestible Lys intake, mg/d 1,063 1,213 1,369 1,535 1,656 1,757 1,938 2,011 2,157 1,860 20 Probabilities 0.001 0.044 0.001 0.99 1.24
Digestible Lys intake:BW gain, mg:g
FCR,2 kg:kg
Mortality, %
14.40 15.29 16.10 16.73 17.69 19.13 20.46 21.80 22.75 18.91 0.20
2.222 2.199 2.036 1.977 1.924 1.918 1.862 1.924 1.895 1.928 0.033
0.8 0.7 0.8 0.7 0.7 0.7 2.2 0.0 0.7 1.5 0.9
0.002 0.003 0.84 0.95 1.66
0.94 0.68 0.54 0.04 76.82
0.001 0.009 0.44 0.99 1.18
1Values are least squares means of 9 replicate pens with 15 broilers per pen at 28 d of age. Grand BW mean at 28 d of age was 1.635 kg and 28-d BW was not significantly different among the treatments (P = 0.21). 2FCR = feed conversion ratio. 3Orthogonal contrast.
DISCUSSION
that extensive variability exists between batches of the same ingredient. Assays determining amino acid requirements should use test diets that are deficient in the amino acid under investigation and adequate in other amino acids. In the current research, the low-Lys diet with no added l-Lys was formulated to contain 0.64% digestible Lys. Amino acid analysis determined that the low-Lys diet had 0.71 and 0.77% total Lys, whereas total Lys for the highLys diets approximated 1.22 and 1.23% for experiments
Diets were formulated based on digestible coefficient ingredients of previously established values (Ajinomoto Heartland LLC, 2009), which were determined from an extensive number of assays. We elected to use digestible coefficients averaged across several assays rather than conducting digestible amino acid assays with feed ingredients or complete feeds due to the variation associated with this measurement. However, we do acknowledge
Table 5. Processing yields of Ross × Ross TP16 male broilers fed gradient levels of digestible Lys from 28 to 42 d of age, experiment 11 Chilled carcass 43-d BW, kg
Weight, kg
Yield, %
Digestible Lys, % 0.64 0.71 0.78 0.85 0.92 0.99 1.06 1.13 1.20 Control (0.99%) SEM Source of variation
2.798 2.876 2.949 3.065 3.060 2.981 3.074 3.036 3.080 3.099 0.037
1.978 2.052 2.127 2.196 2.023 2.169 2.203 2.183 2.229 2.235 0.029
70.7 71.4 72.1 71.6 72.0 72.8 71.7 71.9 72.4 72.1 0.3
Linear trend Quadratic trend Control vs. 0.99%2 R2 CV, %
0.008 0.046 0.027 0.77 1.57
0.005 0.015 0.11 0.89 1.44
Item
1Vaules
0.06 0.15 0.13 0.60 0.61
are least squares means of 9 replicate pens with 5 broilers at 43 d of age. contrast.
2Orthogonal
Abdominal fat Weight, kg 0.067 0.071 0.068 0.069 0.067 0.065 0.063 0.064 0.064 0.065 0.002 Probabilities 0.023 0.79 0.90 0.66 2.36
Total breast
Yield, %
Weight, kg
2.40 2.47 2.31 2.24 2.19 2.20 2.07 2.12 2.10 2.10 0.08
0.575 0.618 0.649 0.678 0.686 0.666 0.684 0.670 0.703 0.683 0.011
0.001 0.33 0.34 0.89 2.35
0.005 0.036 0.32 0.89 2.15
Yield, % 20.5 21.5 22.0 22.1 22.4 22.4 22.2 22.1 22.8 22.0 0.3 0.009 0.07 0.58 0.87 2.15
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BW, kg
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Estimated requirement1
95% CI
SEM
Probability value
Performance BW gain FCR2 Processing yields Carcass weight Carcass yield Breast weight
0.988 1.053 0.939 0.921 0.962
0.909 to 1.066 0.942 to 1.163 0.809 to 1.068 0.784 to 1.061 0.792 to 1.132
0.039 0.055 0.065 0.070 0.085
0.001 0.001 0.001 0.001 0.001
1The quadratic broken-line model is as follows: y = L + U × (R − x) × (R − x), where L is the ordinate, U is the slope of the line at values of x < R, R is the abscissa of the breakpoint, and the value R − is zero at values of x > R. 2FCR = feed conversion ratio.
was estimated at 0.994% when averaged across experiments for feed conversion, growth rate, and total breast meat weight. Han and Baker (1994) determined the digestible Lys requirement at 0.89 and 0.85% for feed conversion and BW gain, respectively, using brokenline analysis for 21- to 42-d-old male Ross broilers. Moreover, digestible Lys requirement for feed conversion was reported at 0.95 and 0.89%, respectively, for Ross and ISA male broilers from 20 to 40 d of age utilizing broken-line methodology (Mack et al., 1999). The higher digestible Lys requirement for the modern broiler compared with birds used in research from previous decades relates to less feed intake per unit of BW gain and a greater rate of meat accretion (Havenstein et al., 2003a,b; Dozier et al., 2008a, 2009a). In the present research, BW gain approximated 92 and 103 g/d for experiments 1 and 2, respectively. The accelerated growth rate of broilers used in the present research resulted in 10 to 12% higher digestible Lys requirements
Table 7. Growth performance of Cobb × Cobb 700 male broilers fed gradient additions of digestible Lys from 28 to 42 d of age, experiment 21
BW, kg
BW gain, kg
Feed intake, kg
Digestible Lys, % 0.64 0.71 0.78 0.85 0.92 0.99 1.06 1.13 1.20 Control (0.99%) SEM Source of variation
2.800 2.961 2.983 3.082 3.114 3.101 3.137 3.092 3.126 3.042 0.020
1.138 1.288 1.326 1.431 1.443 1.450 1.479 1.437 1.454 1.377 0.015
2.473 2.612 2.575 2.644 2.639 2.606 2.643 2.570 2.580 2.557 0.024
Linear response Quadratic response Control vs. 0.99%3 R2 CV, %
0.004 0.002 0.03 0.94 1.01
0.005 0.0007 0.001 0.96 1.84
0.37 0.017 0.16 0.67 1.36
Item
Digestible Lys intake, mg/d 1,130 1,324 1,434 1,605 1,734 1,843 2,001 2,074 2,211 1,808 17 Probabilities 0.0001 0.016 0.15 0.99 1.16
Digestible Lys intake:BW gain, mg:g 13.91 14.39 15.17 15.71 16.82 17.79 18.94 20.20 21.29 18.38 0.11 0.0001 0.0001 0.0003 0.99 0.64
FCR,2 kg:kg
Mortality, %
2.172 2.028 1.941 1.847 1.812 1.789 1.782 1.782 1.774 1.852 0.013
0.3 0.7 0.3 0.3 0.3 1.4 0.7 0.7 0.0 0.3 0.43
0.001 0.0001 0.001 0.98 0.96
0.91 0.28 0.07 0.19 75.37
1Values are least squares means of 12 replicate pens with 23 broilers per pen at 28 d of age. Grand BW mean at 28 d of age was 1.661 kg and 28-d BW was not significantly different among the treatments (P = 0.64). 2FCR = feed conversion ratio. 3Orthogonal contrast.
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1 and 2, respectively. The coefficient of determination for BW gain and feed conversion ranged from 0.94 to 0.98 in experiments 1 and 2, indicating that the lowLys diet was clearly deficient. The control-fed broilers had similar feed conversion and meat yield as birds fed the dose-response diet at 0.99% digestible Lys in experiment 1, and the dose-response diet formulated to 0.99% digestible Lys had better or similar growth performance and meat yield responses than control-fed birds in experiment 2. The good performance observed with the dose-response diets in both experiments provides evidence that digestible Lys requirements were not underestimated. Digestible Lys requirement varied from 0.921 to 1.053% and 0.965 to 1.029% for experiments 1 and 2, respectively, with the estimate being dependent upon the response criterion. Digestible Lys requirement was more pronounced for feed conversion than growth rate or breast meat accretion. Digestible Lys requirement
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Table 8. Processing weights and yields of Cobb × Cobb 700 male broilers fed gradient additions of digestible Lys from 28 to 42 d of age, experiment 21 Chilled carcass Yield,2 %
Digestible Lys, % 0.64 0.71 0.78 0.85 0.92 0.99 1.06 1.13 1.20 Control (0.99%) SEM Source of variation
2.099 2.144 2.236 2.264 2.300 2.300 2.339 2.267 2.335 2.263 0.020
71.2 71.6 71.6 72.5 72.5 72.7 73.1 72.6 72.7 72.9 0.35
Linear response Quadratic response Control vs. 0.99%3 R2 CV, %
0.003 0.014 0.21 0.91 1.26
0.002 0.018 0.81 0.90 0.30
Weight, kg
Yield, %
0.048 1.64 0.046 1.53 0.045 1.45 0.049 1.60 0.045 1.44 0.044 1.39 0.046 1.44 0.042 1.34 0.042 1.33 0.042 1.35 0.001 0.055 Probabilities 0.038 0.002 0.47 0.91 0.37 0.56 0.52 0.74 4.34 4.26
Total breast Weight, kg
Yield, %
0.618 0.656 0.697 0.731 0.752 0.742 0.763 0.730 0.756 0.737 0.009
21.0 21.9 22.3 23.4 23.7 23.4 23.8 23.4 23.5 23.7 0.22
0.004 0.002 0.70 0.94 1.92
0.006 0.001 0.39 0.95 1.06
1Values
are least squares means of 12 replicate pens with 5 broilers per pen processed at 43 d of age. are defined as grams of tissue per 100 g of live weight. 3Orthogonal contrast. 2Yields
when expressed as a percentage of the diet than birds used in previous research. The requirement for feed conversion was approximately 6% higher than for BW gain and total breast meat weight when averaged across both experiments in the research reported herein. Other research has also found higher Lys requirements for feed conversion than BW gain (Han and Baker, 1994; Leclercq, 1998; Baker et al., 2002; Dozier et al., 2008a, 2009a). As digestible Lys exceeds the concentration for the requirement of BW gain, feed intake decreases without a change in BW gain, translating to a higher requirement for feed conversion (Baker et al., 2002). Digestible Lys requirements for feed conversion were determined at 1.05 and 1.01% in experiments 1 and 2, respectively. Feed conversion of broilers fed at optimum digestible Lys requirement differed between the 2 experiments, with broilers in experiment 2 having 0.073 lower feed conversion (1.789 vs. 1.862) than birds in experiment 1. Moreover, broilers in experiment 2 were 163 g heavier and consumed 121 g more feed than birds in experiment 1. The accelerated growth rate exhibited by broilers in experiment 2 may have translated to a lower feed conversion than birds in experiment 1. A direct comparison between experiments is precluded due to differences in experimental facilities, season, genetic strain, pellet quality, feed ingredients, lighting schedule, and management. Postnatal muscle accretion is influenced by an increase in protein synthesis or decreased protein degradation, or both. Insulin-like growth-factor I increases protein synthesis and decreases protein degradation of muscle cells (Vandenburgh et al., 1991). Broilers fed diets varying in dietary CP have been shown to regu-
late IGF-I (Farhat and Chaver, 1999; Tesseraud et al., 2003). Rosebrough et al. (1996) reported a 56% increase in IGF-I plasma concentrations with broilers fed diets formulated to 21.0 versus 12.0% CP. In the current research, it was shown that broilers fed deficient dietary Lys concentrations did not exhibit altered plasma IGFI concentrations. Based on this finding, we chose not to evaluate this measurement in experiment 2. Dietary amino acid requirements for broiler chickens are typically based on growth performance and meat yield measurements. In swine, response criteria for determining amino requirements may include growth performance, carcass yield, and plasma urea nitrogen mea-
Figure 1. Effects of digestible Lys on plasma uric acid concentration (experiment 2). Means are represented by 6 replicates (2 birds per replicate). Error bars denote SEM.
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Weight, kg
Item
Abdominal fat
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Estimated requirement1
95% CI
SEM
Probability value
Performance BW gain FCR2 Processing yields Carcass weight Carcass yield Breast weight Breast yield
0.965 1.012 1.029 0.963 0.987 0.981
0.903 to 1.026 0.969 to 1.055 0.900 to 1.158 0.808 to 1.118 0.906 to 1.068 0.885 to 1.076
0.031 0.021 0.065 0.070 0.040 0.048
0.001 0.001 0.001 0.001 0.001 0.001
1The quadratic broken-line model is as follows: y = L + U × (R − x) × (R − x), where L is the ordinate, U is the slope of the line at values of x < R, R is the abscissa of the breakpoint, and the value R − is zero at values of x > R. 2FCR = feed conversion ratio.
experiment 2 than experiment 1. Broilers fed the doseresponse diet consuming 0.99% digestible Lys consumed 1,843 mg/d of digestible Lys in experiment 2, whereas digestible Lys intake approximated 1,757 mg/d when broilers were fed a diet containing 0.99% digestible Lys in experiment 1. Overall average requirements based on BW gain, feed conversion, and breast meat yield were 1.001 and 0.986%, respectively, for experiments 1 and 2. It is important to note that these requirements were averaged across 2 broiler strains. These data support a higher digestible Lys requirement (0.99%) of male broilers from 28 to 42 d of age on a percentage basis than previous research (Han and Baker, 1994; Leclercq, 1998; Mack et al., 1999) as noted by less feed intake per unit of BW gain and a greater meat accretion rate. Digestible Lys requirements (percentage basis) were in close agreement between strains, indicating that these 2 genetic sources had similar Lys needs to optimize growth and meat yield.
REFERENCES Ajinomoto Heartland LLC. 2009. True Digestibility of Essential Amino Acids for Poultry. Ajinomoto Heartland LLC, Chicago, IL. AOAC. 2006. Official Methods of Analysis. 18th ed. Association of Official Analytical Chemists, Arlington, VA. Baker, D. H., A. B. Batal, T. M. Parr, N. R. Augspurger, and C. M. Parsons. 2002. Ideal ratio (relative to lysine) of tryptophan, threonine, isoleucine, and valine for chicks during the second and third posthatch. Poult. Sci. 81:485–494. Corzo, A., W. A. Dozier III, and M. T. Kidd. 2006. Dietary lysine needs of late-developing heavy broilers. Poult. Sci. 85:457–461. Corzo, A., W. A. Dozier III, R. E. Loar, M. T. Kidd, and P. B. Tillman. 2009. Assessing the threonine-to-lysine ratio of female broilers from 14 to 28 days of age. J. Appl. Poult. Res. 18:237– 243. Corzo, A., E. T. Moran Jr., and D. Hoehler. 2002. Lysine need of heavy broiler males applying the ideal protein concept. Poult. Sci. 81:1863–1868. Corzo, A., E. T. Moran Jr., and D. Hoehler. 2003. Lysine needs of summer-reared male broilers from six to eight weeks of age. Poult. Sci. 82:1602–1607. Donsbough, A. L., S. Powell, A. Waguespack, T. D. Bidner, and L. L. Southern. 2010. Uric acid, urea, and ammonia concentrations in serum and uric acid concentration in excreta as indicators of amino acid utilization in diets for broilers. Poult. Sci. 89:287–294.
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surements. Because uric acid is the main end product in nitrogen metabolism for poultry, plasma uric acid may be a more sensitive measurement for determining amino acid requirements than plasma urea nitrogen. In experiment 2, significant quadratic responses of plasma urea nitrogen and plasma uric acid were not observed for digestible Lys; hence, requirements were not determined. In agreement with the present research, plasma urea concentration was not altered when broilers were fed increasing dietary Lys concentrations (Corzo et al., 2003). Dozier et al. (2009b) reported a decreasing linear response of plasma urea nitrogen with progressive additions of digestible Lys, but a quadratic response was not obtained; therefore, a requirement could not be estimated. In contrast, Donsbough et al. (2010) have reported that serum uric acid, serum urea nitrogen, and excreta uric acid concentrations are indicators of amino acid utilization for broilers. These authors suggested a fasting and refeeding schedule to obtain the most consistent results with blood collection occurring at 2 h refeeding. In the research reported herein and Dozier et al. (2009b), blood was collected with broilers fed ad libitum. Dietary Lys alters carcass composition of broilers (Han and Baker, 1994; Leclercq, 1998; Mack et al., 1999; Corzo et al., 2002, 2006; Dozier et al., 2008a). Lipid accretion rate is decreased by gradient increases of dietary Lys (Han and Baker, 1994; Leclercq, 1998; Mack et al., 1999). Broilers fed diets containing 1.18% total Lys had the lowest abdominal fat percentage, whereas optimum BW gain and feed conversion responses were obtained with 0.92 and 1.01% total dietary Lys (Leclercq, 1998). Significant linear responses were observed for abdominal fat percentage in experiments 1 and 2. Variation was more pronounced with abdominal fat percentage than other response criteria in experiment 2, which may have led to the inability to detect a significant quadratic response. Conversely, abdominal fat percentage was similar with broilers fed progressive concentrations of dietary Lys (Corzo et al., 2006; Dozier et al., 2008a). Digestible Lys intake needed to optimize growth performance and meat yield for male broilers was higher in
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