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Animal Science Department, Faculty of Agriculture, University of Zabol, Zabol, Iran 98661- ..... 2011. Effect of varying dietary energy to protein ratio on produc-.

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 98661-5538 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 91:2958–2962 http://dx.doi.org/10.3382/ps.2012-02170

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, 2012. Accepted July 29, 2012. 1 Corresponding author: [email protected]

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.

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QUAIL ENERGY AND PROTEIN REQUIREMENTS 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 premix1   Mineral premix2 Calculated nutrient analysis   ME (kcal/kg)   CP (%)   Ca (%)   Available P (%)   Digestible Lys (%)   Digestible Met (%)   Digestible Met + Cys (%)   Digestible Thr (%)   Digestible Trp (%)   Digestible Ile (%)   Digestible Val (%)   Digestible Arg (%)  DEB3 (mEq/kg)

1

2

3

4

5

6

7

8

9

56.32 30.99 9.25 — — — 1.41 0.75 0.27 0.16 0.17 0.03 0.15 0.25 0.25

63.34 27.20 — 3.00 1.34 2.00 1.24 0.41 0.54 0.14 0.14 0.02 0.12 0.25 0.25

43.88 35.00 12.24 3.00 2.32 0.85 1.22 0.33 0.04 0.17 0.18 0.03 0.28 0.25 0.25

54.87 29.55 — 3.00 7.36 2.00 1.25 0.37 0.53 0.32 0.15 0.05 0.07 0.25 0.25

51.15 35.00 9.48 1.34 — — 1.31 0.55 0.08 0.12 0.18 0.03 0.27 0.25 0.25

59.97 24.89 — 3.00 6.70 2.00 1.26 0.41 0.71 0.32 0.13 0.05 0.07 0.25 0.25

67.33 26.45 — 3.00 — 0.12 1.24 0.42 0.54 0.11 0.13 0.02 0.13 0.25 0.25

45.64 35.00 6.98 3.00 4.54 2.00 1.22 0.33 0.16 0.22 0.18 0.04 0.20 0.25 0.25

58.01 34.72 — 3.00 — 1.58 1.22 0.35 0.22 0.06 0.17 0.01 0.16 0.25 0.25

2,850 20 0.80 0.30 1.06 0.45 0.72 0.68 0.21 0.76 0.83 1.22 250

3,050 20 0.80 0.30 1.06 0.45 0.71 0.68 0.20 0.76 0.85 1.19 250

2,850 24 0.80 0.30 1.27 0.53 0.85 0.81 0.25 0.92 1.01 1.44 250

3,050 24 0.80 0.30 1.27 0.53 0.85 0.81 0.22 0.90 1.00 1.33 250

2,809 22 0.80 0.30 1.17 0.49 0.79 0.75 0.24 0.84 0.93 1.36 250

3,092 22 0.80 0.30 1.17 0.49 0.79 0.75 0.20 0.82 0.91 1.19 250

2,950 19.2 0.80 0.30 1.02 0.43 0.69 0.65 0.20 0.73 0.81 1.15 250

2,950 24.8 0.80 0.30 1.31 0.55 0.88 0.84 0.25 0.95 1.04 1.45 250

2,950 22 0.80 0.30 1.17 0.49 0.78 0.75 0.24 0.86 0.94 1.38 250

1Vitamin 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 B12, 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. 2Mineral premix provided per kilogram of diet: Mn (from MnSO ·H O), 65 mg; Zn (from ZnO), 55 mg; Fe (from FeSO ·7H O), 50 mg; Cu (from 4 2 4 2 CuSO4·5H2O), 8 mg; I [from Ca(IO3)2·H2O], 1.8 mg; Se, 0.30 mg; Co (from Co2O3), 0.20 mg; Mo, 0.16 mg. 3DEB = dietary electrolyte balance.

Experimental Diets

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

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

Table 2. The ratio of indispensible amino acids to lysine in the experimental diets Experimental diet Amino acid Digestible Digestible Digestible Digestible Digestible Digestible Digestible Digestible

Lys Met Met + Cys Thr Trp Ile Val Arg

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2

3

4

5

6

7

8

9

100 42 68 64 20 72 78 115

100 42 67 64 19 72 80 112

100 42 67 64 20 72 80 113

100 42 67 64 17 71 79 105

100 42 67 64 20 72 79 116

100 42 67 64 17 70 78 102

100 42 67 64 20 72 79 112

100 42 67 64 19 72 79 111

100 42 67 64 20 73 80 117

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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 replications1

BWG (g/bird)

±SD

FCR (g/g)

±SD

4 4 4 4 4 4 4 4 8

35.6 33.3 40.7 39.5 37.2 37.5 32.4 40.9 36.8

1.27 1.36 0.87 1.49 2.28 1.55 1.46 0.74 1.54

2.47 2.50 2.08 2.24 2.37 2.24 2.67 2.14 2.39

0.04 0.10 0.16 0.08 0.14 0.16 0.11 0.06 0.10

1 2 3 4 5 6 7 8 9 1A

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

k

y = β0 + ∑ βi x i + ∑ ∑ βij x i x j + ∑ βii x i2 + ε, i =1

i