PRODUCTION, MODELING, AND EDUCATION. Response surface of dietary energy and protein in Japanese quail from 7 to 14 days of age

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1 PRODUCTION, MODELING, AND EDUCATION Response surface of dietary energy and protein in Japanese quail from 7 to 14 days of age M. Ghazaghi, M. Mehri, 1 M. Yousef-Elahi, and M. Rokouei Animal Science Department, Faculty of Agriculture, University of Zabol, Zabol, Iran ABSTRACT An experiment was conducted to determine dietary energy (ME) and CP requirements of quail chicks using response surface methodology. A total of 40 floor pens of 20 birds each were assigned to 9 diets of central composite design (CCD) containing 5 levels of ME (2,809 to 3,091 kcal/kg) and CP (19 to 24.8% of diet) from 7 to 14 d of age. The experimental results of CCD were fitted with quadratic response models, and ridge analysis was used to compute the optimal response for BW gain (BWG) and feed conversion ratio (FCR). Regression analysis showed that the linear effect of independent variables was significant on bird responses. The quadratic and cross-product effects did not have significant effects on performance. Dietary levels of CP linearly affected BWG and FCR, but the effect of dietary ME was not significant. The ridge maximum analysis on BWG and minimum analysis on FCR models revealed that the maximum BWG may be achieved with 2,950 kcal of ME/kg and 25% CP; and minimum FCR may be obtained with 2,878 kcal of ME/kg and 24.4% CP. The results of this study showed that response surface analysis with the CCD platform was successfully used to optimize dietary requirements of Japanese quail and this methodology could be used for other nutrients. Key words: Japanese quail, energy, protein, response surface 2012 Poultry Science 91 : INTRODUCTION Dietary energy (ME) and CP are main components of the poultry feed. Feed efficiency and growth rate of Japanese quail were increased with increasing dietary ME (Elangovan et al., 2004), and protein deficiency in the starter diet may impair the development of the reproductive system and decreases the laying rate in adult quail (Soares et al., 2003). On the other hand, it has been accepted that the intake of all nutrients could be regulated by the ME concentration of the diet (NRC, 1994). To maintain a constant intake of essential nutrients (e.g., dietary protein), the specific ratio of each nutrient to dietary ME may be considered. Usually, experiments dealing with determination of requirements of ME and CP were based on the ratio of ME:CP resulting from different levels of CP at a constant dietary ME. However, it should be noted that birds with the same ME:CP ratios may have different productivity and determination of ME:CP ratio would not necessarily guarantee profit maximization. Pesti (1991) clearly showed that better models of performance could 2012 Poultry Science Association Inc. Received January 18, Accepted July 29, Corresponding author: mehri@uoz.ac.ir be obtained by including ME and CP as independent variables than by including ME:CP ratio in the model. Therefore, the estimation of ME and CP requirements over the range of dietary inputs would be preferable. The objective of the present study was to optimize dietary ME and CP in quail chick (Coturnix coturnix japonica) for maximum BWG and minimum FCR from 7 to 14 d of age using response surface methodology (RSM). MATERIALS AND METHODS Bird Management A total of 800 one-day-old Japanese quails were obtained from the Research Center of Special Domestic Animals (University of Zabol, Zabol, Iran). The chicks were fed a standard diet containing 2,900 kcal of ME/ kg, 26% CP, 1.25% digestible lysine (dlys), 0.57% digestible methionine (dmet), and 0.87% digestible threonine (dthr) from 0 to 7 d of age. At 7 d, the chicks were weighed and randomly allotted to 40 floor pens (1 m 1.2 m) of 20 birds each so that chicks had a similar initial BW in each pen. The floor pens were equipped with feeder, bell drinker, and wood shavings. The environmental temperature and humidity were kept at 29 C and 60%, respectively, during the study. 2958

2 QUAIL ENERGY AND PROTEIN REQUIREMENTS 2959 Table 1. Composition of experimental diets based on central composite design Item Ingredient (%) Corn, grain Soybean meal, 44% Wheat, grain Fish meal Corn gluten meal Soybean oil Oyster shell Dicalcium phosphate Sodium bicarbonate l-lys HCl dl-met l-thr NaCl Vitamin premix Mineral premix Calculated nutrient analysis ME (kcal/kg) 2,850 3,050 2,850 3,050 2,809 3,092 2,950 2,950 2,950 CP (%) Ca (%) Available P (%) Digestible Lys (%) Digestible Met (%) Digestible Met + Cys (%) Digestible Thr (%) Digestible Trp (%) Digestible Ile (%) Digestible Val (%) Digestible Arg (%) DEB 3 (meq/kg) Vitamin premix provided per kilogram of diet: vitamin A (from vitamin A acetate), 11,500 IU; cholecalciferol, 2,100 IU; vitamin E (from dl-αtocopheryl acetate), 22 IU; vitamin B 12, 0.60 mg; riboflavin, 4.4 mg; nicotinamide, 40 mg; calcium pantothenate, 35 mg; menadione (from menadione dimethyl-pyrimidinol), 1.50 mg; folic acid, 0.80 mg; thiamine, 3 mg; pyridoxine, 10 mg; biotin, 1 mg; choline chloride, 560 mg; ethoxyquin, 125 mg. 2 Mineral premix provided per kilogram of diet: Mn (from MnSO 4 H 2 O), 65 mg; Zn (from ZnO), 55 mg; Fe (from FeSO 4 7H 2 O), 50 mg; Cu (from CuSO 4 5H 2 O), 8 mg; I [from Ca(IO 3 ) 2 H 2 O], 1.8 mg; Se, 0.30 mg; Co (from Co 2 O 3 ), 0.20 mg; Mo, 0.16 mg. 3 DEB = dietary electrolyte balance. Experimental Diets Before feed formulation, all protein-containing feed ingredients were analyzed for CP and profile of amino acids using near infrared reflectance spectroscopy (Fontaine et al., 2001, 2002). Because of a lack of information on digestibility coefficients of amino acids for quail chicks, digestible amino acid values were calculated from the digestible coefficients for broiler chicks (Degussa, 2010) and analyzed total amino acid content of the ingredients. The experimental diets were formulated based on a central composite design (CCD) pattern to produce 9 treatments (Table 1) providing 5 levels of ME (2,809 to 3,091 kcal/kg) and CP (19 to 24.8% of diet). To keep amino acid profile over the range of experimental CP, the level of dlys was set as 5.3% of CP and remaining essential amino acid including digestible arginine, isoleucine, methionine plus cystine, dmet, dthr, tryptophan, and valine were at least 102, 70, 67, 42, 64, 17, and 78% of dlys, respectively (Table 2). Four replicates were allocated to 8 dietary treatments (e.g., 4 star and 4 factorial points of design), whereas 8 replicates were assigned to the central point of the CCD platform. Adding center points is useful for detecting nonlinearity in the response. Replicated center points also provide an estimate of variance. A 2-factor, 5-level CCD platform was used to fit the second-order models of bird performance. The mean of each pen was used as the experimental unit in the Table 2. The ratio of indispensible amino acids to lysine in the experimental diets Experimental diet Amino acid Digestible Lys Digestible Met Digestible Met + Cys Digestible Thr Digestible Trp Digestible Ile Digestible Val Digestible Arg

3 2960 Ghazaghi et al. Table 3. Experimental response values for BW gain (BWG) and feed conversion ratio (FCR) of quail chicks to different dietary concentrations of ME (kcal/kg) and CP (%) based on central composite design Treatment no. No. of replications 1 BWG (g/bird) ±SD FCR (g/g) ±SD A total of 40 run numbers were provided. statistical analysis. The linear, quadratic, and crossproduct terms for independent variables were evaluated. The general polynomial equation was as follows: k y = β + β x + β xx + β x + ε, 0 i i ij i j i= 1 i< j i= 1 where y is response of the birds (BWG and FCR), β 0 is the intercept, and β i, β ii and β ij are the coefficients estimated by the model; x i represents the input variables (dietary energy and protein concentrations), and ε is the residual associated with the experiment (Mehri, et al., 2012). All data were analyzed by SAS using RSREG procedure. A ridge analysis was also applied to compute the optimal response for BWG and FCR using RIDGE MAX and RIDGE MIN, respectively (SAS, 2002). k RESULTS AND DISCUSSION ii 2 i The bird responses to dietary treatments are shown in Table 3. The first task in analyzing the response surface is to estimate the parameters of the model by least-squares regression. The linear term significantly affected BWG and FCR, but the quadratic and interactive effects were not significant. Analysis of residual did not show lack of fit for the BWG and FCR models (Table 4). The R 2 value for BWG and FCR models was 0.79 and 0.69, respectively; indicating that 70 to 80% of variability in the responses could be explained by RSM models (Figure 1 and 2). The polynomial equations from raw (uncoded) experimental data (SAS, 2002) for BWG (R 2 = 0.79, root MSE = 1.49) and FCR (R 2 = 0.69; root MSE = 0.11) were as follows: BWG (g) = (ME) 2.3(CP) (ME) (ME CP) 0.002(CP) 2. FCR (g/g) = (ME) 0.60(CP) (ME) (ME CP) (CP) 2. The second task in analyzing the response surface is to examine the overall shape of the curve and determine whether the estimated stationary point is a maximum, a minimum, or a saddle point. Canonical analysis showed that the stationary point for both BWG and FCR models is a saddle point. A saddle point yields neither a maximum nor a minimum for the fitted model and has one positive and one negative real eigenvalue, Table 4. Analysis of variance on the experimental results and contribution of each regression term to the statistical fit in response to the surface model for BW gain (BWG) and feed conversion ratio (FCR) of Japanese quail from 7 to 14 d of age BWG model FCR model Source of variation df Sum of squares R 2 P-value Sum of squares R 2 P-value Regression Linear Quadratic Cross-product Total model Residual Lack of fit Pure error Total error Independent variable Dietary ME Dietary CP

4 QUAIL ENERGY AND PROTEIN REQUIREMENTS 2961 Figure 1. Scatter plot of observed vs. predicted values for BW gain (g/bird) of Japanese quail from 7 to 14 d of age. The solid line represents the fitted simple linear regression on scatter points. Figure 2. Scatter plot of observed vs. predicted values for feed conversion ratio (g/g) of Japanese quail from 7 to 14 d of age. The solid line represents the fitted simple linear regression on scatter points. Table 5. Eigenvectors of independent variables for BW gain (BWG) and feed conversion ratio (FCR) Eigenvalue ME CP BWG FCR which are shown in Table 5. In this case, the response value grows as we move away from the surface centersaddle along one axis, and falls along the other axis. The moving direction depends on the target of the researcher and what the researcher is interested in, the maximum or the minimum (Lazić, 2004). For this purpose, ridge analysis could be performed. Ridge analysis computes the estimated ridge of the optimum response for increasing radii from the center of the origin design. The ridge maximum analysis on BWG to optimize response revealed that the maximum BWG may be obtained with 2,950 kcal of ME/kg and 25% CP of diet, whereas the ridge minimum analysis on FCR model indicated that the minimum FCR may be obtained with 2,878 kcal of ME/kg and 24.4% CP of diet. The predicted BWG and FCR at the optimum points were 40.9 g/bird and 2.12 g/g, respectively. The performance of quail chicks improved with increasing dietary protein and was optimized at intermediate energy level, and optimum ME:CP ratio was obtained by 118 (Table 6). Estimation of ME and CP requirements of Japanese quail before sexual maturity is very important because their deficiency may impair the laying rate in the subsequent period (Soares et al., 2003). In this study, the ME requirement was estimated at 2,950 kcal/kg, which was higher than reported by Elangovan et al. (2004). Environmental temperature has a profound effect on the ME requirement, and experimental conditions of these 2 studies may cause this differences. The CP requirement was optimized at 25% of diet, which is higher than those reported by Lee et al. (1977), Shim and Vohra (1984), and Soares et al. (2003). The optimum dietary CP increases the bird performance and the growth depression due to low-protein diets may be related to the low amino acid profile of such diet. On the other hand, breeding companies are improving the commercial strains, and part of these differences may be related to the genetic potential of modern Japanese quail. Siyadati et al. (2011) studied different ratios of ME:CP in Japanese quail and concluded the best ME:CP ratio for starting Japanese quail (0 to 21 d of age) was 107, and it could be increased up to 120 during the finisher period (21 to 45 d of age). However, Pesti (1991) noted that the hens on diets with the same ME:CP ratio may have different productivity, so determination the requirements of each nutrient (e.g., ME and CP) would be critical. In contrast, Tarasewicz et al. (2006) concluded that neither dietary ME or CP level, but rather the ME:CP ratio is the important factor affecting adult quail performance. The major discrepancy between previous reports and our study may be attributed to the experimental methodology and statistical analysis. It is well recognized that poultry have a requirement for indispensible amino acids (IAA) and low-cp diets fortified with crystalline amino acid improve bird performance (Han et al., 1992; Kerr and Kidd, 1999). Therefore, altering the ratio of IAA in the diet may affect performance. In the present study, we kept the ratios of all IAA over the range of experimental treatments (Table 4), which was not considered in some previous reports. Also regarding statistical methods, Pesti et al. (2009) stressed the importance of analyzing continuous data with regression models. In most experiments for determination of dietary requirement of ME and CP in Japanese quail, Table 6. Optimum values of dietary energy and CP for BW gain (BWG) and feed conversion ratio (FCR) in Japanese quail from 7 to 14 d of age with ridge analysis Item BWG FCR ME (kcal/kg) 2,950 2,878 CP (% of diet) ME:CP ratio

5 2962 Ghazaghi et al. Duncan s multiple range has been used (Lee et al., 1977; Shim and Vohra, 1984; Elangovan et al., 2004; Siyadati et al., 2011), which may influence the results. In fact, in such dose-response experiments we are looking for an estimation of a dietary nutrient that optimized performance using the appropriate model. Regression analysis could estimate the optimal point, but the mean comparison approach makes it impossible. In conclusion, a platform of RSM models with ridge analysis was used successfully to estimate the ME and CP requirements of quail chick and 2,950 kcal of ME/ kg and 25% CP resulted in optimum performance. Although the estimated ME and CP for FCR were lower than BWG (2,878 vs. 2,950 kcal/kg and 24.4 vs. 25% of diet, respectively), the same ME:CP ratio for BWG and FCR was achieved (ME:CP = 118). Because of limited information on the nutritional requirements of modern Japanese quail, further studies are warranted to precise feed formulation and profit maximizing. REFERENCES Degussa AmioDat 4.0. Rodenbacher Chaussee, Hanau-Wolfgang, Germany. Elangovan, A. V., A. B. Mandal, P. K. Tyagi, S. Toppo, and T. S. Johri Effects of enzymes in diets with varying energy levels on growth and egg production performance of Japanese quail. J. Sci. Food Agric. 84: Fontaine, J., J. Hörr, and B. Schirmer Near-infrared reflectance spectroscopy enables the fast and accurate prediction of the essential amino acid contents in soy, rapeseed meal, sunflower meal, peas, fishmeal, meat meal products, and poultry meal. J. Agric. Food Chem. 49: Fontaine, J., B. Schirmer, and J. Hörr Near-infrared reflectance spectroscopy (NIRS) enables the fast and accurate prediction of essential amino acid contents. 2. Results for wheat, barley, corn, triticale, wheat bran/middlings, rice bran, and sorghum. J. Agric. Food Chem. 50: Han, Y., H. Suzuki, C. M. Parsons, and D. H. Baker Amino acid fortification of a low-protein corn and soybean meal diet for chicks. Poult. Sci. 71: Kerr, B. J., and M. T. Kidd Amino acid supplementation of low-protein broiler diets: 1. Glutamic acid and indispensable amino acid supplementation. J. Appl. Poult. Res. 8: Lazić, Ž. R Design of experiments in chemical engineering: A practical guide. Vch Verlagsgesellschaft Mbh, Freiburg, Germany. Lee, T. K., K. F. Shim, and E. L. Tan Protein requirement of growing Japanese quail in the tropics. Singapore Journal of Primary Industries 5: Mehri, M., A. A. Davarpanah, and H. R. Mirzaei Estimation of ideal ratios of methionine and threonine to lysine in starting broiler chicks using response surface methodology. Poult. Sci. 91: NRC Nutrient Requirements for Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC. Pesti, G. M Response surface approach to studying the protein and energy requirements of laying hens. Poult. Sci. 70: Pesti, G. M., D. Vedenov, J. A. Cason, and L. Billard A comparison of methods to estimate nutritional requirements from experimental data. Br. Poult. Sci. 50: SAS SAS/STAT 9.1 User s Guide. SAS Institute Inc., Cary, NC. Shim, K., and P. Vohra A review of the nutrition of Japanese quail. World s Poult. Sci. J. 40: Siyadati, S. A., M. Irani, K. Ghazvinian, A. Mirzaei-Aghsaghali, V. Rezaipoor, H. Fathi, K. Alipoor, and S. Zamanzad-Ghavidel Effect of varying dietary energy to protein ratio on productive performance and carcass characteristics of Japanese quail. Ann. Biol. Res. 2: Soares, R. T. R. N., J. B. Fonseca, A. S. O. Santos, and M. B. Mercandante Protein requirement of Japanese quail (Coturnix coturnix japonica) during rearing and laying periods. Rev. Brasileira Ciê. Aví. 5: Tarasewicz, Z., M. L. Szczerbińska, M. Wiercińska, and K. R. Majewska The effect of differentiated dietary protein level on the performance of breeder quails. Anim. Sci. Pap. Rep. 24: