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Growth performance of male broilers fed diets varying in digestible threonine to lysine ratio from 1 to 14 days of age1
C 2015 Poultry Science Association Inc.
Growth performance of male broilers fed diets varying in digestible threonine to lysine ratio from 1 to 14 days of age1 W. A. Dozier, III,∗,2 K. J. Meloche,∗ P. B. Tillman,† and Z. Jiang‡ Department of Poultry Science, Auburn University, Auburn, AL 36849; † Poultry Technical Nutrition Services, Buford, GA 30518; and ‡ Ajinomoto Heartland Inc., Chicago, IL
Primary Audience: Live Production Personnel, Nutritionists SUMMARY Threonine (Thr) is the third limiting amino acid for broilers fed corn-soybean meal–based diets. Digestible Thr to lysine (Lys) ratios utilized by commercial nutritionists vary from 0.63 to 0.68 in the starter period. Low Thr to Lys ratios used during the early growth period can limit performance. This study examined growth responses of broilers provided experimental diets varying in digestible Thr from 1 to 14 d of age. Dietary treatments were formulated at 8 digestible Thr to Lys ratios (0.55, 0.58, 0.61, 0.64, 0.67, 0.70, 0.73, and 0.76). Two diets (dilution and summit) consisting of corn and soybean meal were formulated to be adequate in all other amino acids with the exception of Thr and Lys. All diets were formulated to contain 1.13% digestible Lys, which is slightly below the digestible Lys requirement for male broilers from 1 to 14 d of age. Digestible Thr to Lys ratios were estimated using broken-line methodology. Linear (P = 0.003) and quadratic (P = 0.005) increases in body weight gain (BWG) were observed for broilers fed progressive additions of digestible Thr. Additionally, linear (P < 0.001) and quadratic (P = 0.018) improvements in feed conversion were observed as digestible Thr consumption increased. Based on linear broken-line methodology, optimal digestible Thr to Lys ratios for Ross × Ross 708 male broilers for BWG and feed conversion were 0.66 and 0.69, respectively. These data support a minimum digestible Thr to Lys ratio of 0.67 for male broilers from 1 to 14 d of age when averaged for BWG and feed conversion. Key words: amino acid, broiler, threonine 2015 J. Appl. Poult. Res. 24:457–462 http://dx.doi.org/10.3382/japr/pfv047
INTRODUCTION Threonine is the third limiting amino acid for broilers fed corn-soybean meal–based diets after total sulfur amino acids (TSAA) and lysine (Lys) [1,2]. Threonine is utilized for mucin and intesti1
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. 2 Corresponding author: [email protected]
nal development, lean meat accretion, feather development, and enzyme formation [3–6]. The ideal protein concept is a popular method to express amino acid requirements relative to Lys [7]. The advantage of this formulation strategy is that when the requirements for Lys have been determined for various weight classes, the ratios for the other essential amino acids can be determined for any given set of factors (gender, age, strain, diet, and growth rate). Amino acid ratios should not change based on dietary
Downloaded from http://japr.oxfordjournals.org/ at Orta Dogu Teknik University Library (ODTU) on February 1, 2016
∗
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MATERIALS AND METHODS Bird Husbandry One thousand, five hundred thirty-six Hubbard × Cobb 500 male chicks were randomly
distributed into 64 floor pens at 1 d of age with 24 birds per pen (0.09 m2 per bird) in a solid-sided house equipped with vent boards, minimum ventilation fans, and electronic controller. Chicks were vaccinated for Marek’s disease, Newcastle disease, and infectious bronchitis at the hatchery. Lighting was set at 30 lux at placement and subsequently dimmed to 10 lux and 5 lux at 7 and 12 d post hatch, respectively. Photoperiod was set to 23L:1D from placement to 7 d of age, and then set to 18L:6D for the remainder of the experiment. Ambient temperature was set at 33◦ C prior to placement, and decreased gradually to a final set point of 27◦ C at the end of the experiment.
Dietary Treatments Corn, soybean meal, distillers’ dried grains with solubles, and peanut meal were analyzed [14] for total amino acids and CP composition prior to diet formulation. Digestible amino acid values for the ingredients used in diet formulation were determined by applying digestibility coefficients [15] to the analyzed total amino acid content of the ingredients. Two diets [dilution (negative control) and summit] were formulated to be adequate in all other amino acids with the exception of Thr and Lys (Table 1). The dilution and summit diets were blended to create 6 intermediate diets, for a total of 8 titration diets resulting in digestible Thr ranging from 0.62 to 0.86% by increments of 0.3% (Table 2). The dilution diet was formulated to be deficient in digestible Thr and was considered as a negative control. All diets were formulated to contain 1.13% digestible Lys, which is slightly below the digestible Lys requirement for Hubbard × Cobb male broilers from 1 to 14 d of age [13] in order to prevent overestimation of the optimal Thr to Lys ratio. Birds received 8 experimental diets from 1 to 14 d of age with each treatment being represented by 8 replicate pens. Body weight was measured at d 1 and d 14 post hatch. Body weight gain, feed intake, digestible Thr intake, digestible Thr intake/BWG, feed conversion ratio, and mortality were assessed for the experimental period.
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nutrient specifications such as protein and energy content. Published values for digestible Thr to Lys ratios in young chicks have been inconsistent [8,9,10]. Rostagno [8] reported a digestible Thr to Lys ratio of 0.65 for 1- to 21-day-old broilers, however, this result was in disagreement with research conducted with older broilers estimating an optimum digestible Thr to Lys ratio 0.68 [11,12]. Neto et al. [9] conducted research in male Cobb 500 broilers from 1 to 7 d, in which a digestible Thr to Lys ratio of 0.65 was determined for body weight gain (BWG), while other measurements (fat content, fat deposition, and crude protein / fat content ratio) provided estimates between 0.68 and 0.69. Moreover, Mehri et al. [10] evaluated responses of Met, Lys, and Thr in 3 to 16 d old Ross × Ross 708 male broilers using a central composite design. Body weight gain and feed conversion were maximized with digestible Thr to Lys ratios of 0.70 and 0.66, respectively. However, these data were based upon only 24 chicks per treatment and the ratios were based upon 5 treatments from each amino acid. Higher Lys requirements and digestible TSAA to Lys ratios have recently been reported with Ross × Ross 708 and Cobb × Cobb 500 chicks from 1 to 14 d of age compared with previous research [12,13]. The increased amino acid requirements may be attributable to the selection of broilers for higher lean meat accretion, and consequently the higher rate of muscle cell development during first few weeks post hatch. Hence, research is warranted to ascertain an optimum digestible Thr to Lys ratio of broilers having the potential of high lean meat accretion during the starter period. Therefore, the objective of this study was to determine a digestible threonine to digestible lysine ratio to optimize growth performance of male Hubbard × Cobb 500 broilers from 1 to 14 d of age.
DOZIER ET AL.: THREONINE NEEDS OF BROILERS IN THE STARTER PHASE 459 Table 1. Ingredient and calculated composition of diets formulated with low or high dietary Thr concentrations fed to Hubbard × Cobb 500 male broilers from 1 to 14 d of age. Ingredient, % “as-fed”
Dilution Diet 59.96 21.60 6.00 4.00 3.00 1.43 1.21 0.93 0.35 0.33 0.25 0.25 0.25 – 0.16 0.11 0.08 0.03 0.01 0.05
Calculated Analysis6 , % basis unless otherwise noted 3,019 AMEn , kcal/kg CP 20.90 Digestible Lys 1.13 Digestible TSAA 0.87 Digestible Thr 0.62 Digestible Val 0.88 Digestible Ile 0.78 Digestible Trp 0.20 Digestible Arg 1.23 Ca 0.98 Non-phytate P 0.48 Na 0.22
Summit Diet Blended7
59.72 21.60 6.00 4.00 3.00 1.43 1.21 0.93 0.35 0.33 0.25 0.25 0.25 0.24 0.16 0.11 0.08 0.03 0.01 0.05
3,020 21.10 1.13 0.87 0.86 0.88 0.78 0.20 1.23 0.98 0.48 0.22
DDGS = distillers’ dried grains with solubles; SBOM = Soybean meal; PBM = Poultry by-product meal. Vitamin premix provided 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, 5.4 mg; niacin (niacinamide), 45 mg; thiamine (thiamine mononitrate), 1 mg; D-biotin, 0.05 mg; pyridoxine (pyridoxine hydrochloride), 2.2 mg; and choline (choline chloride), 500 mg. 3 Mineral premix provided 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; Se (sodium selenite), 0.3 mg. 4 Phytase from DSM, Parsippany, NJ. 5 BioCox 60 provided 60 g/907 kg of salinomycin (Alpharma, Fort Lee, NJ). 6 Values reported as percentages unless noted otherwise. Digestible amino acid values were determined from digestibility coefficients and calculated total amino acid content of the ingredients [15]. 7 Low- and high-Thr diets were blended in specific ratios to create 6 additional treatments (Table 2). 1 2
Statistics Growth performance data was analyzed as a one-way treatment structure in a randomized complete block design with pen location as the blocking factor, and pen was considered the ex-
perimental unit. All data was analyzed by PROC MIXED [16] using a mixed model with fixed treatment effects and a random blocking effect. Linear and quadratic effects were determined using PROC REG [16] on all growth performance measures. Digestible Thr to Lys ratios
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Corn SBOM1 Peanut Meal DDGS1 PBM1 Poultry oil Calcium carbonate Defluorinated P L-Lysine-HCl DL-Methionine Vitamin Premix2 Mineral Premix3 Sodium chloride L-Threonine Sodium bicarbonate L-Valine L-Isoleucine L-Tryptophan Phytase4 Salinomycin5
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460 Table 2. Specific blends of high- and low-Thr basal diets to create the 8 treatment diets with progressive increases in dietary Thr fed to Hubbard × Cobb 500 male broilers from 1 to 14 d of age. Diet Blend Digestible Thr to Lys Ratio1
Low-Thr Basal, %
High-Thr Basal, %
1 2 3 4 5 6 7 8
0.55 0.58 0.61 0.64 0.67 0.70 0.73 0.76
100.0 85.7 71.5 57.2 42.8 28.5 14.3 0.0
0.0 14.3 28.6 28.5 57.2 71.5 85.7 100.0
1 Calculated digestible Thr to Lys ratio; digestible Lys content was 1.13% in all treatment diets.
were estimated using broken-line methodology using PROC NLIN [16] according to the method of Robbins et al. [17].
RESULTS AND DISCUSSION Amino acid requirement studies should utilize a dose-response diet that is deficient in the test amino acid to generate accurate requirement estimates. In the current research, the diet formulated to contain the lowest Thr concentration was determined to be deficient in Thr. Total Thr concentrations generally increased with the dose-
Table 3. Growth performance of Hubbard × Cobb 500 male broilers fed diets varying in digestible (dig) Thr from 1 to 14 d of age.1 BW (kg)
BWG (kg)
Feed Intake (kg)
1 0.55 (NC)3 2 0.58 3 0.61 4 0.64 5 0.67 6 0.70 7 0.73 8 0.76 SEM4 Source of Variation
0.466 0.478 0.485 0.491 0.489 0.500 0.502 0.494 0.004
0.424 0.435 0.444 0.447 0.446 0.458 0.459 0.452 0.004
0.526 0.532 0.532 0.532 0.532 0.539 0.542 0.529 0.005
Linear Quadratic Linear R2 Quadratic R2
0.003 0.006 0.79 0.93
0.003 0.005 0.80 0.92
0.19 0.23 0.27 0.44
Treatment
1
Dig Thr to Dig Lys ratio
Thr Intake (mg) 233 248 262 271 287 304 319 324 2.9 Probabilities 0.001 0.08 0.99 0.99
Values are least-square means of 8 replicate pens with 24 broilers per pen at 1 d of age. Feed conversion ratio corrected for mortality. 3 NC = negative control. 4 Pooled standard error. 2
Thr Intake/ BWG (mg/g)
FCR2
Mortality (%)
7.72 8.00 8.27 8.59 9.03 9.31 9.74 10.04 0.04
1.243 1.221 1.200 1.189 1.191 1.176 1.180 1.170 0.006
1.68 0.54 1.63 1.63 1.09 1.09 1.63 1.63 0.81
0.001 0.018 0.86 0.96
0.77 0.72 0.042 0.10
0.001 0.08 0.99 0.99
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Treatment
response diets and were determined to be 0.79, 0.82, 0.82, 0.86, 0.88, 0.93, 0.93, and 0.95%, for diets formulated to contain digestible Thr to Lys ratio of 0.55, 0.58, 0.61, 0.64, 0.67, 0.70, 0.73, and 0.76, respectively. Moreover, dose-response diets should be marginal in Lys so a ratio can be accurately determined. Total Lys concentrations of the dose-response diets were 1.29, 1.31, 1.28, 1.30, 1.32, 1.34, 1.30, and 1.30%, for diets formulated to contain digestible Thr to Lys ratios of 0.55, 0.58, 0.61, 0.64, 0.67, 0.70, 0.73, and 0.76, respectively. These results indicate that the diets were marginal when compared with the Lys requirement estimates reported by previous research [13]. Progressive additions of digestible Thr increased BWG and decreased feed conversion ratio quadratically (P ≤ 0.02) in broiler chicks from 1 to 14 d of age (Table 3). Treatment 1 (digestible Thr to Lys ratio of 0.55) was considered the negative control. Broilers receiving this treatment had 8% lower BWG and 6% higher feed conversion when compared with treatment 6 (digestible Thr to Lys of 0.67). Feed intake and the incidence of mortality were similar for broilers fed the 8 dietary treatments. Digestible Thr intake and digestible Thr intake/BWG increased (P ≤ 0.001) with broilers consuming diets containing gradient concentrations of digestible Thr. Broilers consumed 287 and 304 mg
DOZIER ET AL.: THREONINE NEEDS OF BROILERS IN THE STARTER PHASE 461 Table 4. Digestible Thr to Lys ratios of male Hubbard × Cobb 500 broilers from 1 to 14 d of age based on 2 broken-line model analyses. Response Criteria Quadratic Model2 BWG (kg) Feed conversion ratio (kg:kg) Linear Model3 BWG (kg) Feed conversion ratio (kg:kg)
Estimated Ratio
95% CI1
SEM
Probability Value
0.738 0.734
0.64–0.83 0.68–0.79
0.048 0.028
0.0001 0.0001
0.658 0.686
0.62–0.70 0.66–0.71
0.019 0.014
0.0001 0.0001
95% confidence interval of the digestible Thr to Lys ratio. The one-slope quadratic broken-line model is y = L + V × (z1) × (z1) where L is the asymptote segment (L), V is the slope for the line segment, and z1 = (x < R) ∗ (R – x) is defined as zero if (x > R). 3 The linear broken-line model is y = L + U × (R – x), where L is the ordinate, R is the abscissa of the break point, and the value (R – x) is zero at values of x > R. 2
of digestible Thr when provided diets formulated to contain digestible Thr to Lys ratios of 0.67 and 0.70, respectively, from 1 to 14 d of age. Optimal digestible Thr to Lys ratios for BWG and feed conversion ratio were determined at 0.66 and 0.68 based on linear broken-line methodology and 0.74 and 0.73 determined with quadratic broken-line methodology, respectively (Table 4). Broilers having the potential of high lean meat accretion have higher amino acid needs than birds used in previous research [12–13], and the ratio estimates reported herein support previous research using Ross × Ross TP16 broilers from 14 to 28 d of age [11]. It is important to note that the chicks used in the present research were raised in very well controlled conditions (management, environment, disease control, and prevention), but this may not be the case when these birds are raised under commercial settings. Digestible Thr to Lys ratios for optimum performance have varied in the published literature. Rostagno et al. [8] reported an optimal digestible Thr to Lys ratio of 0.65 for broiler chicks from 1 to 21 d of age. Neto et al. [9] examined the digestible Thr to Lys ratio in Cobb 500 broiler chicks from 1 to 7 d of age. Six digestible Thr ratios were provided ranging from 0.50 to 0.75 in increments of 0.06 to 0.07. A digestible Thr to Lys ratio of 0.65 was estimated for BWG, but a minimum ratio was not estimated for feed conversion ratio. Mehri et al. [9] evaluated digestible Met, Lys, and Thr responses on the basis of response surface methodology. The experimental design consisted of 15 dietary treatments in a central composite, rotatable design containing 5 concentrations of digestible Met (0.42 to 0.58%), digestible Lys (0.88 to 1.32%), and di-
gestible Thr (0.53 to 0.87%) fed to Ross × Ross 308 male broilers. Digestible Thr to Lys ratios were estimated at 0.70 and 0.66, respectively, for BWG and feed conversion, which was based on digestible Lys at 1.12 and 1.13% for BWG and feed conversion. These results were only based on 24 birds per treatment, whereas the current study utilized 192 broilers per treatment. Conversely, Baker et al. [7] reported a digestible Thr to Lys ratio of 0.56 of New Hampshire × Columbian Plymouth broiler chicks from 7 to 21 d post hatch. This digestible Thr to Lys ratio was based on nutrient excretion data. It is important to note that the chicks used in that study are not representative of broilers used in commercial practice. Estimates for amino acid requirements can vary due to statistical analysis [18]. The straightline analysis may underestimate the requirement with curvilinear data, whereas the quadraticbroken line model can overestimate the requirement [17]. In the current research, digestible Thr to Lys ratios for BWG and feed conversion varied among the straight and quadratic broken-line models. The linear broken-line models for BWG and feed conversion had smaller numerical differences for the 95% confidence intervals and SEM compared with the quadratic broken-line models. Hence, the linear brokenline model was a better fit for the data set than the quadratic broken-line model. The requirement for feed conversion was higher than the estimate for BWG with the linear broken-line model, but requirement estimates for the 2 response variables were similar when the quadratic broken-line model was used.
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CONCLUSIONS AND APPLICATIONS
REFERENCES AND NOTES 1. Han, Y., H. Suzuki, C. M. Parsons, and D. H. Baker. 1992. Amino acid fortification of a low-protein corn and soybean meal diet for chicks. Poult. Sci. 71:1168–1178. 2. Baker, D. H., and Y. Han. 1994. Ideal amino acid profile for chicks during the first three weeks posthatching. Poult. Sci. 73:1441–1447. 3. Kidd, M. T., and B. J. Kerr. 1996. L-Threonine for poultry: A review. J. Appl. Poult. Res. 5:358–367. 4. Kidd, M. T. 2000. Nutritional considerations concerning threonine in broilers. World’s Poult. Sci. J. 56:139– 151. 5. Dozier, W. A., III, E. T. Moran, and M. T. Kidd. 2001. Male and female broiler responses to low and adequate dietary threonine on nitrogen and energy balance. Poult. Sci. 80:926–930. 6. Horn, N. L., S. S. Donkin, T. J. Applegate, and O. Adeola. 2009. Intestinal mucin dynamics: response of broiler chicks and White Pekin ducklings to dietary threonine. Poult. Sci. 88:1906–1914. 7. Baker, D. H., A. B. Batal, T. M. Parr, N. R. Augspurger, and C. M. Parsons. 2002. Ideal ratio (relative to
Downloaded from http://japr.oxfordjournals.org/ at Orta Dogu Teknik University Library (ODTU) on February 1, 2016
1. Broilers fed progressive additions of digestible Thr resulted in linear and quadratic improvements in BWG and feed conversion ratio. 2. Optimal digestible Thr to Lys ratios for Hubbard × Cobb 500 male broilers for BWG and feed conversion were 0.66 and 0.69, respectively, based on linear brokenline methodology. Quadratic broken-line methodology determined optimal digestible Thr to Lys ratios for BWG and feed conversion at 0.74 and 0.73, respectively. 3. Broilers fed diets formulated to contain digestible Thr to Lys ratios of 0.67 and 0.70 had digestible Thr intakes of 287 and 304 mg, respectively, from 1 to 14 d of age.
lysine) of tryptophan, threonine, isoleucine, and valine for chicks during the second and third weeks posthatch. Poult. Sci. 81:485–494. 8. Rostagno, H. R., L. F. T. Albino, J. L. Donzele, P. C. Gomes, R. F. de Olveira, D. C. Lopes, A. S. Firiera, and S. L. de T. Barreto. 2011. Brazilian Tables for Poultry and Swine. Composition of Feedstuffs and Nutritional Requirements. 3rd ed. In Rostagno, H. S., ed. Universidade Federal de Vicosa, Dept. Zootecnia, Vicosa, MG, Brazil. 9. Neto, R. C. L., F. G. P. Costa, R. L. Furlan, P. E. N. Givisiez, C. C. Goulart, C. F. S. Oliveira, S. A. N. Morais, R. M. Bezzera, and M. R. Lima. 2012. Levels of digestible threonine for male broilers from 1 to 7 days of age. J. Appl. Poult. Res. 21:757–763. 10. Mehri, M., A. A. Davarpanah, and H. R. Miraei. 2012. Estimation of ideal ratios of methionine and threonine to lysine in starting broiler chicks using response surface methodology. Poult. Sci. 91:771–777. 11. 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. 12. Dozier, W. A., III, and Y. Mercier. 2013. Ratio of digestible total sulfur amino acids to lysine of broiler chicks from 1 to 15 days of age. J. Appl. Poult. Res. 22:862–871. 13. Dozier, W. A., III, and R. L. Payne. 2012. Digestible Lys requirements of female broilers from 1 to 15 days of age. J. Appl. Poult. Res. 21:348–357. 14. Association of Official Analytical Chemists International. 2006. Official Methods of Analysis. 18th ed. Association of Official Analytical Chemists, Arlington, VA. Total amino acids were determined accordingly by the methods of AOAC International, 2006; 985.28, 994.12, whereas CP composition was estimated by the standard procedure of AOAC International, 2006; 968.06. 15. Ajinomoto Heartland LLC. 2009. True Digestibility of Essential Amino Acids for Poultry. Ajinomoto Heartland LLC, Chicago, IL. http://aaa. lysine.com/AATable/Ingredients.aspx R User’s Guide. Statistics. 16. SAS Institute. 2004. SAS Version 9.1 ed. SAS Institute Inc., Cary, NC. 17. Robbins, K. R., A. M. Saxton, and L. L. Southern. 2006. Estimation of nutrient requirements using broken-line regression analysis. J. Anim. Sci. 84: E155-E165. 18. Pesti, G. M., D. Vedenov, J. Cason, and L. Billard. 2009. A comparison of methods to estimate nutritional requirements from experimental data. Br. Poult. Sci. 50: 16–32.
Growth performance of male broilers fed diets varying in digestible threonine to lysine ratio from 1 to 14 days of age1 W. A. Dozier, III,∗,2 K. J. Meloche,∗ P. B. Tillman,† and Z. Jiang‡ Department of Poultry Science, Auburn University, Auburn, AL 36849; † Poultry Technical Nutrition Services, Buford, GA 30518; and ‡ Ajinomoto Heartland Inc., Chicago, IL
Primary Audience: Live Production Personnel, Nutritionists SUMMARY Threonine (Thr) is the third limiting amino acid for broilers fed corn-soybean meal–based diets. Digestible Thr to lysine (Lys) ratios utilized by commercial nutritionists vary from 0.63 to 0.68 in the starter period. Low Thr to Lys ratios used during the early growth period can limit performance. This study examined growth responses of broilers provided experimental diets varying in digestible Thr from 1 to 14 d of age. Dietary treatments were formulated at 8 digestible Thr to Lys ratios (0.55, 0.58, 0.61, 0.64, 0.67, 0.70, 0.73, and 0.76). Two diets (dilution and summit) consisting of corn and soybean meal were formulated to be adequate in all other amino acids with the exception of Thr and Lys. All diets were formulated to contain 1.13% digestible Lys, which is slightly below the digestible Lys requirement for male broilers from 1 to 14 d of age. Digestible Thr to Lys ratios were estimated using broken-line methodology. Linear (P = 0.003) and quadratic (P = 0.005) increases in body weight gain (BWG) were observed for broilers fed progressive additions of digestible Thr. Additionally, linear (P < 0.001) and quadratic (P = 0.018) improvements in feed conversion were observed as digestible Thr consumption increased. Based on linear broken-line methodology, optimal digestible Thr to Lys ratios for Ross × Ross 708 male broilers for BWG and feed conversion were 0.66 and 0.69, respectively. These data support a minimum digestible Thr to Lys ratio of 0.67 for male broilers from 1 to 14 d of age when averaged for BWG and feed conversion. Key words: amino acid, broiler, threonine 2015 J. Appl. Poult. Res. 24:457–462 http://dx.doi.org/10.3382/japr/pfv047
INTRODUCTION Threonine is the third limiting amino acid for broilers fed corn-soybean meal–based diets after total sulfur amino acids (TSAA) and lysine (Lys) [1,2]. Threonine is utilized for mucin and intesti1
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. 2 Corresponding author: [email protected]
nal development, lean meat accretion, feather development, and enzyme formation [3–6]. The ideal protein concept is a popular method to express amino acid requirements relative to Lys [7]. The advantage of this formulation strategy is that when the requirements for Lys have been determined for various weight classes, the ratios for the other essential amino acids can be determined for any given set of factors (gender, age, strain, diet, and growth rate). Amino acid ratios should not change based on dietary
Downloaded from http://japr.oxfordjournals.org/ at Orta Dogu Teknik University Library (ODTU) on February 1, 2016
∗
JAPR: Research Report
458
MATERIALS AND METHODS Bird Husbandry One thousand, five hundred thirty-six Hubbard × Cobb 500 male chicks were randomly
distributed into 64 floor pens at 1 d of age with 24 birds per pen (0.09 m2 per bird) in a solid-sided house equipped with vent boards, minimum ventilation fans, and electronic controller. Chicks were vaccinated for Marek’s disease, Newcastle disease, and infectious bronchitis at the hatchery. Lighting was set at 30 lux at placement and subsequently dimmed to 10 lux and 5 lux at 7 and 12 d post hatch, respectively. Photoperiod was set to 23L:1D from placement to 7 d of age, and then set to 18L:6D for the remainder of the experiment. Ambient temperature was set at 33◦ C prior to placement, and decreased gradually to a final set point of 27◦ C at the end of the experiment.
Dietary Treatments Corn, soybean meal, distillers’ dried grains with solubles, and peanut meal were analyzed [14] for total amino acids and CP composition prior to diet formulation. Digestible amino acid values for the ingredients used in diet formulation were determined by applying digestibility coefficients [15] to the analyzed total amino acid content of the ingredients. Two diets [dilution (negative control) and summit] were formulated to be adequate in all other amino acids with the exception of Thr and Lys (Table 1). The dilution and summit diets were blended to create 6 intermediate diets, for a total of 8 titration diets resulting in digestible Thr ranging from 0.62 to 0.86% by increments of 0.3% (Table 2). The dilution diet was formulated to be deficient in digestible Thr and was considered as a negative control. All diets were formulated to contain 1.13% digestible Lys, which is slightly below the digestible Lys requirement for Hubbard × Cobb male broilers from 1 to 14 d of age [13] in order to prevent overestimation of the optimal Thr to Lys ratio. Birds received 8 experimental diets from 1 to 14 d of age with each treatment being represented by 8 replicate pens. Body weight was measured at d 1 and d 14 post hatch. Body weight gain, feed intake, digestible Thr intake, digestible Thr intake/BWG, feed conversion ratio, and mortality were assessed for the experimental period.
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nutrient specifications such as protein and energy content. Published values for digestible Thr to Lys ratios in young chicks have been inconsistent [8,9,10]. Rostagno [8] reported a digestible Thr to Lys ratio of 0.65 for 1- to 21-day-old broilers, however, this result was in disagreement with research conducted with older broilers estimating an optimum digestible Thr to Lys ratio 0.68 [11,12]. Neto et al. [9] conducted research in male Cobb 500 broilers from 1 to 7 d, in which a digestible Thr to Lys ratio of 0.65 was determined for body weight gain (BWG), while other measurements (fat content, fat deposition, and crude protein / fat content ratio) provided estimates between 0.68 and 0.69. Moreover, Mehri et al. [10] evaluated responses of Met, Lys, and Thr in 3 to 16 d old Ross × Ross 708 male broilers using a central composite design. Body weight gain and feed conversion were maximized with digestible Thr to Lys ratios of 0.70 and 0.66, respectively. However, these data were based upon only 24 chicks per treatment and the ratios were based upon 5 treatments from each amino acid. Higher Lys requirements and digestible TSAA to Lys ratios have recently been reported with Ross × Ross 708 and Cobb × Cobb 500 chicks from 1 to 14 d of age compared with previous research [12,13]. The increased amino acid requirements may be attributable to the selection of broilers for higher lean meat accretion, and consequently the higher rate of muscle cell development during first few weeks post hatch. Hence, research is warranted to ascertain an optimum digestible Thr to Lys ratio of broilers having the potential of high lean meat accretion during the starter period. Therefore, the objective of this study was to determine a digestible threonine to digestible lysine ratio to optimize growth performance of male Hubbard × Cobb 500 broilers from 1 to 14 d of age.
DOZIER ET AL.: THREONINE NEEDS OF BROILERS IN THE STARTER PHASE 459 Table 1. Ingredient and calculated composition of diets formulated with low or high dietary Thr concentrations fed to Hubbard × Cobb 500 male broilers from 1 to 14 d of age. Ingredient, % “as-fed”
Dilution Diet 59.96 21.60 6.00 4.00 3.00 1.43 1.21 0.93 0.35 0.33 0.25 0.25 0.25 – 0.16 0.11 0.08 0.03 0.01 0.05
Calculated Analysis6 , % basis unless otherwise noted 3,019 AMEn , kcal/kg CP 20.90 Digestible Lys 1.13 Digestible TSAA 0.87 Digestible Thr 0.62 Digestible Val 0.88 Digestible Ile 0.78 Digestible Trp 0.20 Digestible Arg 1.23 Ca 0.98 Non-phytate P 0.48 Na 0.22
Summit Diet Blended7
59.72 21.60 6.00 4.00 3.00 1.43 1.21 0.93 0.35 0.33 0.25 0.25 0.25 0.24 0.16 0.11 0.08 0.03 0.01 0.05
3,020 21.10 1.13 0.87 0.86 0.88 0.78 0.20 1.23 0.98 0.48 0.22
DDGS = distillers’ dried grains with solubles; SBOM = Soybean meal; PBM = Poultry by-product meal. Vitamin premix provided 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, 5.4 mg; niacin (niacinamide), 45 mg; thiamine (thiamine mononitrate), 1 mg; D-biotin, 0.05 mg; pyridoxine (pyridoxine hydrochloride), 2.2 mg; and choline (choline chloride), 500 mg. 3 Mineral premix provided 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; Se (sodium selenite), 0.3 mg. 4 Phytase from DSM, Parsippany, NJ. 5 BioCox 60 provided 60 g/907 kg of salinomycin (Alpharma, Fort Lee, NJ). 6 Values reported as percentages unless noted otherwise. Digestible amino acid values were determined from digestibility coefficients and calculated total amino acid content of the ingredients [15]. 7 Low- and high-Thr diets were blended in specific ratios to create 6 additional treatments (Table 2). 1 2
Statistics Growth performance data was analyzed as a one-way treatment structure in a randomized complete block design with pen location as the blocking factor, and pen was considered the ex-
perimental unit. All data was analyzed by PROC MIXED [16] using a mixed model with fixed treatment effects and a random blocking effect. Linear and quadratic effects were determined using PROC REG [16] on all growth performance measures. Digestible Thr to Lys ratios
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Corn SBOM1 Peanut Meal DDGS1 PBM1 Poultry oil Calcium carbonate Defluorinated P L-Lysine-HCl DL-Methionine Vitamin Premix2 Mineral Premix3 Sodium chloride L-Threonine Sodium bicarbonate L-Valine L-Isoleucine L-Tryptophan Phytase4 Salinomycin5
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460 Table 2. Specific blends of high- and low-Thr basal diets to create the 8 treatment diets with progressive increases in dietary Thr fed to Hubbard × Cobb 500 male broilers from 1 to 14 d of age. Diet Blend Digestible Thr to Lys Ratio1
Low-Thr Basal, %
High-Thr Basal, %
1 2 3 4 5 6 7 8
0.55 0.58 0.61 0.64 0.67 0.70 0.73 0.76
100.0 85.7 71.5 57.2 42.8 28.5 14.3 0.0
0.0 14.3 28.6 28.5 57.2 71.5 85.7 100.0
1 Calculated digestible Thr to Lys ratio; digestible Lys content was 1.13% in all treatment diets.
were estimated using broken-line methodology using PROC NLIN [16] according to the method of Robbins et al. [17].
RESULTS AND DISCUSSION Amino acid requirement studies should utilize a dose-response diet that is deficient in the test amino acid to generate accurate requirement estimates. In the current research, the diet formulated to contain the lowest Thr concentration was determined to be deficient in Thr. Total Thr concentrations generally increased with the dose-
Table 3. Growth performance of Hubbard × Cobb 500 male broilers fed diets varying in digestible (dig) Thr from 1 to 14 d of age.1 BW (kg)
BWG (kg)
Feed Intake (kg)
1 0.55 (NC)3 2 0.58 3 0.61 4 0.64 5 0.67 6 0.70 7 0.73 8 0.76 SEM4 Source of Variation
0.466 0.478 0.485 0.491 0.489 0.500 0.502 0.494 0.004
0.424 0.435 0.444 0.447 0.446 0.458 0.459 0.452 0.004
0.526 0.532 0.532 0.532 0.532 0.539 0.542 0.529 0.005
Linear Quadratic Linear R2 Quadratic R2
0.003 0.006 0.79 0.93
0.003 0.005 0.80 0.92
0.19 0.23 0.27 0.44
Treatment
1
Dig Thr to Dig Lys ratio
Thr Intake (mg) 233 248 262 271 287 304 319 324 2.9 Probabilities 0.001 0.08 0.99 0.99
Values are least-square means of 8 replicate pens with 24 broilers per pen at 1 d of age. Feed conversion ratio corrected for mortality. 3 NC = negative control. 4 Pooled standard error. 2
Thr Intake/ BWG (mg/g)
FCR2
Mortality (%)
7.72 8.00 8.27 8.59 9.03 9.31 9.74 10.04 0.04
1.243 1.221 1.200 1.189 1.191 1.176 1.180 1.170 0.006
1.68 0.54 1.63 1.63 1.09 1.09 1.63 1.63 0.81
0.001 0.018 0.86 0.96
0.77 0.72 0.042 0.10
0.001 0.08 0.99 0.99
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Treatment
response diets and were determined to be 0.79, 0.82, 0.82, 0.86, 0.88, 0.93, 0.93, and 0.95%, for diets formulated to contain digestible Thr to Lys ratio of 0.55, 0.58, 0.61, 0.64, 0.67, 0.70, 0.73, and 0.76, respectively. Moreover, dose-response diets should be marginal in Lys so a ratio can be accurately determined. Total Lys concentrations of the dose-response diets were 1.29, 1.31, 1.28, 1.30, 1.32, 1.34, 1.30, and 1.30%, for diets formulated to contain digestible Thr to Lys ratios of 0.55, 0.58, 0.61, 0.64, 0.67, 0.70, 0.73, and 0.76, respectively. These results indicate that the diets were marginal when compared with the Lys requirement estimates reported by previous research [13]. Progressive additions of digestible Thr increased BWG and decreased feed conversion ratio quadratically (P ≤ 0.02) in broiler chicks from 1 to 14 d of age (Table 3). Treatment 1 (digestible Thr to Lys ratio of 0.55) was considered the negative control. Broilers receiving this treatment had 8% lower BWG and 6% higher feed conversion when compared with treatment 6 (digestible Thr to Lys of 0.67). Feed intake and the incidence of mortality were similar for broilers fed the 8 dietary treatments. Digestible Thr intake and digestible Thr intake/BWG increased (P ≤ 0.001) with broilers consuming diets containing gradient concentrations of digestible Thr. Broilers consumed 287 and 304 mg
DOZIER ET AL.: THREONINE NEEDS OF BROILERS IN THE STARTER PHASE 461 Table 4. Digestible Thr to Lys ratios of male Hubbard × Cobb 500 broilers from 1 to 14 d of age based on 2 broken-line model analyses. Response Criteria Quadratic Model2 BWG (kg) Feed conversion ratio (kg:kg) Linear Model3 BWG (kg) Feed conversion ratio (kg:kg)
Estimated Ratio
95% CI1
SEM
Probability Value
0.738 0.734
0.64–0.83 0.68–0.79
0.048 0.028
0.0001 0.0001
0.658 0.686
0.62–0.70 0.66–0.71
0.019 0.014
0.0001 0.0001
95% confidence interval of the digestible Thr to Lys ratio. The one-slope quadratic broken-line model is y = L + V × (z1) × (z1) where L is the asymptote segment (L), V is the slope for the line segment, and z1 = (x < R) ∗ (R – x) is defined as zero if (x > R). 3 The linear broken-line model is y = L + U × (R – x), where L is the ordinate, R is the abscissa of the break point, and the value (R – x) is zero at values of x > R. 2
of digestible Thr when provided diets formulated to contain digestible Thr to Lys ratios of 0.67 and 0.70, respectively, from 1 to 14 d of age. Optimal digestible Thr to Lys ratios for BWG and feed conversion ratio were determined at 0.66 and 0.68 based on linear broken-line methodology and 0.74 and 0.73 determined with quadratic broken-line methodology, respectively (Table 4). Broilers having the potential of high lean meat accretion have higher amino acid needs than birds used in previous research [12–13], and the ratio estimates reported herein support previous research using Ross × Ross TP16 broilers from 14 to 28 d of age [11]. It is important to note that the chicks used in the present research were raised in very well controlled conditions (management, environment, disease control, and prevention), but this may not be the case when these birds are raised under commercial settings. Digestible Thr to Lys ratios for optimum performance have varied in the published literature. Rostagno et al. [8] reported an optimal digestible Thr to Lys ratio of 0.65 for broiler chicks from 1 to 21 d of age. Neto et al. [9] examined the digestible Thr to Lys ratio in Cobb 500 broiler chicks from 1 to 7 d of age. Six digestible Thr ratios were provided ranging from 0.50 to 0.75 in increments of 0.06 to 0.07. A digestible Thr to Lys ratio of 0.65 was estimated for BWG, but a minimum ratio was not estimated for feed conversion ratio. Mehri et al. [9] evaluated digestible Met, Lys, and Thr responses on the basis of response surface methodology. The experimental design consisted of 15 dietary treatments in a central composite, rotatable design containing 5 concentrations of digestible Met (0.42 to 0.58%), digestible Lys (0.88 to 1.32%), and di-
gestible Thr (0.53 to 0.87%) fed to Ross × Ross 308 male broilers. Digestible Thr to Lys ratios were estimated at 0.70 and 0.66, respectively, for BWG and feed conversion, which was based on digestible Lys at 1.12 and 1.13% for BWG and feed conversion. These results were only based on 24 birds per treatment, whereas the current study utilized 192 broilers per treatment. Conversely, Baker et al. [7] reported a digestible Thr to Lys ratio of 0.56 of New Hampshire × Columbian Plymouth broiler chicks from 7 to 21 d post hatch. This digestible Thr to Lys ratio was based on nutrient excretion data. It is important to note that the chicks used in that study are not representative of broilers used in commercial practice. Estimates for amino acid requirements can vary due to statistical analysis [18]. The straightline analysis may underestimate the requirement with curvilinear data, whereas the quadraticbroken line model can overestimate the requirement [17]. In the current research, digestible Thr to Lys ratios for BWG and feed conversion varied among the straight and quadratic broken-line models. The linear broken-line models for BWG and feed conversion had smaller numerical differences for the 95% confidence intervals and SEM compared with the quadratic broken-line models. Hence, the linear brokenline model was a better fit for the data set than the quadratic broken-line model. The requirement for feed conversion was higher than the estimate for BWG with the linear broken-line model, but requirement estimates for the 2 response variables were similar when the quadratic broken-line model was used.
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CONCLUSIONS AND APPLICATIONS
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1. Broilers fed progressive additions of digestible Thr resulted in linear and quadratic improvements in BWG and feed conversion ratio. 2. Optimal digestible Thr to Lys ratios for Hubbard × Cobb 500 male broilers for BWG and feed conversion were 0.66 and 0.69, respectively, based on linear brokenline methodology. Quadratic broken-line methodology determined optimal digestible Thr to Lys ratios for BWG and feed conversion at 0.74 and 0.73, respectively. 3. Broilers fed diets formulated to contain digestible Thr to Lys ratios of 0.67 and 0.70 had digestible Thr intakes of 287 and 304 mg, respectively, from 1 to 14 d of age.
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