Feeding programs and their effects on broiler performance and economic indexes

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DESCRIPTION OF PROBLEM

The adoption of new technologies in the

Brazilian poultry industry has evolved greatly

when compared with other agricultural

activi-ties, and all this evolution is directly linked to

new achievements in feed. According to ABEF

[1], Brazil is the third largest producer and the

largest exporter of poultry meat, despite the

cri-ses that often plague the country. The Brazilian

poultry industry currently produces the world’s

least expensive poultry, with acknowledged

quality, exporting to over 150 countries. This

progress has improved the main technical

in-dexes, such as feed conversion, age at slaughter,

and mortality.

However, maintaining this success depends

on several factors, such as a stable economic

policy that encourages the sector, stability in

grain production, trained and qualified

Feeding programs and their effects on broiler

performance and economic indexes

R. B. Trevisan ,

1

_{V. S. Nakagi , P. T. Bravo , and D. E. Faria}

Departamento de Zootecnia, Faculdade de Zootecnia e Engenharia de Alimentos,

Universidade de São Paulo, Pirassununga, SP, 13635-900, Brazil

Primary Audience:

Nutritionists, Researchers, Farm Managers, Poultry Extension

Personnel

SUMMARY

Different feeding programs were evaluated with the aim of comparing broiler performance

and economic indexes. Twelve hundred birds were subjected to a completely randomized

ex-perimental design with 5 treatments and 8 replicates with 30 birds per exex-perimental unit. The

feeding programs were based on Cobb Vantress manual (T1), NRC values (T2), and previous

research by Rostagno (T3, T4) and a modified Rostagno diet (T5). Feed intake, BW, weight

gain, feed conversion, viability, energy consumption, caloric conversion, productive efficiency

index, and carcass characteristics were evaluated in the period from 1 to 46 d of age. The

gross trade margin was calculated for economic analysis. The results were evaluated based on

a variance analysis, and the Tukey test was used to compare treatment means. For performance

characteristics, metabolizable energy consumption was similar for treatments T1, T3, and T5,

but was higher for treatment T2 than T1 and T4. Caloric conversion was higher for treatment

T2 than other treatments, and no differences were noted for other performance characteristics.

It was concluded that the T1 feeding program, based on the Cobb Vantress manual, resulted in

higher trade gross margin ($0.821), whereas T2, based on NRC values, was lower ($0.762).

Therefore, the recommendations contained in the Cobb Vantress manual should be used as a

means of achieving greater profitability in broiler production.

Key words:

carcass yield , economic analysis , nutritional recommendation , performance , poultry

2014 J. Appl. Poult. Res. 23 :1–12

http://dx.doi.org/ 10.3382/japr.2013-00884

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cians, and quality genetic material [2]. Today,

the most important factor in poultry production

is feed costs, currently at about 70% [3]. With

the changes in the prices of key input, such as

corn and soybeans, it is necessary to define

strat-egies that allow for better financial results. To

achieve this, it is important to determine the best

feed-formulation strategy.

Thus, technologies have been sought to

in-crease the efficiency and quality of the feed

provided to the birds [3]. Those technologies

in-clude determining nutrient levels for each stage

of development. To have an optimal

feed-for-mulation program, it is necessary to determine

the nutritional requirements for a specific phase

production, feed composition, ingredients costs,

and other related factors. This scenario poses a

challenge to feed formulators because dealing

with cost-benefit ratios requires integrating

bio-logical and economic aspects [4]. Different

nu-tritional recommendations coming from various

regions of Brazil and from several other

coun-tries, distant from the Brazilian climate and

pro-ductive reality, have also been a problem when

establishing the best nutritional

recommenda-tion for broilers [5].

To formulate an appropriate diet (i.e., one

that achieves the maximum performance and

economic results), it is necessary to know the

birds’ nutritional requirements at each stage

of development. It is important to review the

broilers’ nutritional requirements, as the

con-stant progress made in breeding results in the

accumulation of protein mass in the carcass. In

this regard, it is pertinent to evaluate nutrient

requirements while considering the genetic and

sex differences, because the guidelines featured

in the main tables may be outdated [6].

Cobb 500 Slow Feather is the strain of

broil-ers most reared by the Brazilian industry. From

an applied point of view, this is a good

oppor-tunity to compare scientific publications [7–9]

with the Cobb Vantress manual [10].

Consid-ering that the nutritional requirements of the

current high-yield broiler chicken are different

from those raised several years ago and that

sev-eral formulation strategies exist, the purpose of

our study was to compare feeding programs and

evaluate their effects on the economic indexes

of male Cobb 500 Slow Feather broilers.

MATERIALS AND METHODS

Birds and Experimental Design

All procedures used in our experiment were

approved by the Ethics Committee on

Ani-mal Use from the Universidade de São Paulo.

Twelve hundred 1-d-old male Cobb 500 Slow

Feather [10] commercial chicks were used,

weighing an average of 44.50 g and originating

from 43-wk-old commercial breeders. The

ex-periment lasted 46 d. Bird distribution was made

based on a completely randomized design, with

5 treatments and 8 replications, totaling 40

ex-perimental units with 30 birds each. Treatments

consisted of 5 different feeding programs, based

on recommendations in the Cobb 500 broilers

supplement of growing and nutrition (

T1

) [10];

by the NRC (

T2

) [7]; by Rostagno (

T3

and

T4

)

[8, 9]; and by modifying the levels of Met

rela-tive to Lys (

T5

) from Rostagno [9]. The feeding

stages were set pursuant to each

recommenda-tion.

Experimental Diets

All diets were formulated according to the

requirement of each stage and respecting the

nu-tritional levels of each manual. The composition

of all diets was based on corn and soybean meal

and were divided into phases according to each

recommendation, with T1 divided into periods

of 1 to 10 (prestarter stage), 11 to 22 (starter

stage), 23 to 42 (growth stage), and 43 to 46 d

(finisher stage). For T2, the periods were divided

in 1 to 21 (starter stage), 22 to 42 (growth stage),

and 43 to 46 d (finisher stage). Treatments 3, 4,

and 5, meanwhile, were divided into 1 to 7

(pre-starter stage), 8 to 21 ((pre-starter stage), 22 to 33

(growth I stage), 34 to 42 (growth II stage), and

43 to 46 d (finisher stage). The percentage and

calculated composition of the experimental diets

are shown in Tables 1, 2, 3, 4, and 5.

Characteristics Evaluated

The birds, experimental diets, and feed

left-overs were weighed weekly to monitor bird

de-velopment. Dead animals were recorded daily.

Performance characteristics were calculated

weekly as feed intake (

FI

), BW, weight gain

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(

WG

), FCR, viability (

V

), metabolizable energy

consumption (

MEC

), and caloric conversion

(

CC

). The productive efficiency index (

PEI

)

was calculated at 46 d.

Feed intake was determined based on the

dif-ference between the total feed fed to the birds

and the leftovers of each experimental unit

di-vided by the corrected number of birds (i.e.,

considering mortality to correct the number of

birds) [11]. The results were shown in grams

per bird. Weight gain was calculated as the

dif-ference between the average bird weight at end

of the period (g) and the average bird weight at

the beginning of the period (g). Feed conversion

ratio was calculated by dividing the total feed

the animals consumed and weight gain

consider-Table 1. Percentage and calculated composition of prestarter diets1

Item Treatment T1 T3 T4 T5 Ingredient (%) Corn 60.670 59.076 57.991 58.041 45% soybean meal 32.696 34.224 35.344 35.275

60% corn gluten meal 1.000 1.000 1.000 1.000

Soybean oil 1.298 0.892 1.090 1.064 Dicalcium phosphate 2.098 1.933 1.920 1.921 Limestone 0.928 0.872 0.814 0.815 Salt 0.441 0.450 0.439 0.439 Sodium bicarbonate 0.015 0.015 0.015 0.015 l-Lys HCl 0.168 0.487 0.403 0.405 dl-Met 0.242 0.401 0.376 0.418 l-Thr — 0.206 0.163 0.164 Choline chloride 0.030 0.030 0.030 0.030 Supplement2 _0.400 _0.400 _0.400 _0.400 Antioxidant3 _0.015 _0.015 _0.015 _0.015 Total 100.00 100.00 100.00 100.00 Calculated level ME (kcal/kg) 2,988 2,960 2,960 2,960 CP (%) 21.00 22.11 22.40 22.40 Calcium (%) 1.000 0.942 0.920 0.920 Chlorine (%) 0.297 0.301 0.294 0.294 Available phosphorus (%) 0.500 0.471 0.470 0.470 Sodium (%) 0.220 0.224 0.220 0.220 Potassium (%) 0.786 0.809 0.827 0.826 Linoleic acid (%) 2.095 1.856 1.951 1.937 Total Arg (%) 1.332 — — — Total Met (%) 0.571 — — — Total Thr (%) 0.803 — — — Total Trp (%) 0.252 — — — Total Val (%) 0.939 — — — Digestible Arg (%) — 1.291 1.323 1.321 Digestible Lys (%) 1.080 1.363 1.324 1.324 Digestible Met (%) — 0.689 0.670 0.710

Digestible Met + Cys (%) 0.800 0.968 0.953 0.993

Digestible Thr (%) — 0.886 0.861 0.861

Digestible Trp (%) — 0.233 0.239 0.238

Digestible Val (%) — 0.855 0.873 0.872

1_{T1 = Cobb Vantress [10]: 1 to 10 d; T3 = Rostagno [8]; T4 = Rostagno [9]; and T5 = Rostagno [9] modified: 1 to 7 d.} 2_{Vitamin, mineral, and additive supplementation per kilogram of feed: iron, 12,500 g; manganese, 17,500 g; zinc, 12,500 g;} copper 24,950 g ; iodine, 300 mg; selenium, 50 mg; vitamin A, 1,750,000 IU; vitamin D3, 550,000 IU; vitamin E, 2,750 IU; vitamin K, 400 mg; vitamin B1, 500 mg; vitamin B2, 1,250 mg; vitamin B6, 750 mg; vitamin B12, 3,000 µg; niacin, 8,750 mg; choline, 82,000 g; pantothenic acid, 3,250 mg; folic acid, 200 mg; phytase, 125,000 ftu (units of phytase activity); monensin sodium, 25 g; halquinol, 7,500 mg.

3_{Feedguard: Butil Hidroxi Toulen (minimum) 3%; ethoxyquin (minimum) 11.3%; terc-butil-hidroquinona (minimum) 1%,} citric acid (minimum) 4%.

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ing the correction by mortality (i.e., birds dying

during the experimental period are added to the

final weight), and this result is subtracted from

the initial weight of the experimental unit [11].

Viability was calculated as (shown in

percent-age) V = 100% − mortality %. The MEC was

determined by adding feed consumption in each

feeding phase (g/bird) multiplied by the

cor-responding ME (expressed in kilocalories per

bird). Caloric conversion was determined based

Table 2. Percentage and calculated composition of starter diets1

Item Treatment T1 T2 T3 T4 T5 Ingredient (%) Corn 65.764 52.627 60.016 60.509 60.555 45% soybean meal 27.251 32.628 32.585 32.468 32.404

60% corn gluten meal 1.000 5.826 1.000 1.000 1.000

Soybean oil 1.795 5.000 2.155 1.950 1.925 Dicalcium phosphate 2.024 1.832 1.826 1.566 1.566 Limestone 0.913 1.099 0.842 0.859 0.860 Salt 0.372 0.404 0.437 0.417 0.417 Sodium bicarbonate 0.015 — 0.015 0.015 0.015 l-Lys HCl 0.216 0.004 0.314 0.352 0.354 dl-Met 0.236 0.135 0.290 0.322 0.361 l-Thr — — 0.107 0.127 0.128 Choline chloride — 0.030 — — — Supplement2 _0.400 _0.400 _0.400 _0.400 _0.400 Antioxidant3 _0.015 _0.015 _0.015 _0.015 _0.015 Total 100.00 100.00 100.00 100.00 100.00 Calculated level ME (kcal/kg) 3,083 3,200 3,050 3,050 3,050 CP (%) 19.00 23.00 21.14 21.20 21.20 Calcium (%) 0.960 1.000 0.899 0.841 0.841 Chlorine (%) 0.257 0.270 0.294 0.282 0.282 Available phosphorus (%) 0.480 0.450 0.449 0.401 0.401 Sodium (%) 0.190 0.200 0.218 0.210 0.210 Potassium (%) 0.701 0.773 0.782 0.781 0.780 Linoleic acid (%) 2.421 3.940 2.544 2.442 2.430 Total Arg (%) 1.171 1.297 — — — Total Lys (%) — 1.100 — — — Total Met (%) 0.539 0.530 — — —

Total Met + Cys (%) — 0.900 — — —

Total Thr (%) 0.723 0.876 — — — Total Trp (%) 0.219 0.260 — — — Total Val (%) 0.844 0.906 — — — Digestible Arg (%) — — 1.243 1.241 1.239 Digestible Lys (%) 0.990 — 1.189 1.217 1.217 Digestible Met (%) — — 0.572 0.604 0.641

Digestible Met + Cys (%) 0.750 — 0.844 0.876 0.913

Digestible Thr (%) — — 0.773 0.791 0.791

Digestible Trp (%) — — 0.224 0.223 0.223

Digestible Val (%) — — 0.827 0.827 0.826

1_{T1 = Cobb Vantress [10]: 11 to 22 d; T2 = NRC [7]: 1 to 21 d; T3 = Rostagno[8]; T4 = Rostagno [9]; and T5 = Rostagno [9]} modified: 8 to 21 d.

2_{Vitamin, mineral, and additive supplementation per kilogram of feed: iron, 12,500 g; manganese, 17,500 g; zinc, 12,500 g;} copper, 24,950 g; iodine, 300 mg; selenium, 50 mg; vitamin A, 1,750,000 IU; vitamin D3, 550,000 IU; vitamin E, 2,750 IU; vitamin K, 400 mg; vitamin B1, 500 mg; vitamin B2, 1,250 mg; vitamin B6, 750 mg; vitamin B12, 3,000 µg; niacin, 8,750 mg; choline, 82,000 g; pantothenic acid, 3,250 mg; folic acid, 200 mg; phytase, 125,000 ftu (units of phytase activity); monensin sodium, 25 g; halquinol, 7,500 mg.

3_{Feedguard: butyl hidroxi toulen (minimum) 3%; ethoxyquin (minimum) 11.3%; terc-butil-hidroquinona (minimum) 1%, citric} acid (minimum) 4%.

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on the ratio between MEC and WG (shown in

kilocalories per kilogram of weight gain). The

PEI was calculated using the formula: PEI =

[(daily WG × V)/(FC × 10)].

At 46 d of age, 3 birds per experimental unit

were selected randomly for carcass yield,

com-mercial cuts, and relative abdominal fat weight

assessments. The birds had fasted from feed

Table 3. Percentage and calculated composition of grower I diets1

60% corn gluten meal 1.000 0.211 1.000 1.000 1.000

Soybean oil 2.861 4.801 3.145 2.903 2.893 Dicalcium phosphate 1.881 1.302 1.683 1.335 1.335 Limestone 0.869 1.187 0.800 0.819 0.819 Salt 0.375 0.267 0.416 0.396 0.396 Sodium bicarbonate 0.015 0.015 0.015 0.015 0.015 l-Lys HCl 0.244 — 0.306 0.347 0.347 dl-Met 0.250 0.0847 0.267 0.301 0.336 l-Thr — — 0.095 0.117 0.117 Choline chloride 0.006 0.006 0.006 0.006 0.006 Supplement2 _0.400 _0.400 _0.400 _0.400 _0.400 Antioxidant3 _0.015 _0.015 _0.015 _0.015 _0.015 Total 100.00 100.00 100.00 100.00 100.00 Calculated level ME (kcal/kg) 3,176 3,200 3,150 3,150 3,150 CP (%) 18.00 20.00 19.73 19.84 19.86 Calcium (%) 0.900 0.900 0.837 0.758 0.758 Chlorine (%) 0.260 0.192 0.282 0.270 0.270 Available phosphorus (%) 0.450 0.350 0.418 0.354 0.354 Sodium (%) 0.190 0.150 0.208 0.200 0.200 Potassium (%) 0.659 0.774 0.725 0.726 0.726 Linoleic acid (%) 3.010 3.959 3.107 2.986 2.981 Total Arg (%) 1.091 1.315 — — — Total Lys (%) — 1.050 — — — Total Met (%) 0.538 0.398 — — —

Total Met + Cys (%) — 0.720 — — —

Digestible Thr (%) — — 0.714 0.735 0.735

Digestible Trp (%) — — 0.204 0.204 0.204

Digestible Val (%) — — 0.769 0.771 0.771

1_{Grower: T1 = Cobb Vantress [10]: 23 to 42 d; T2 = NRC [7]: 22 to 42 d; Grower I: T3 = Rostagno [8]; T4 = Rostagno [9]; and} T5 = Rostagno [9] modified: 22 to 33 d.

2_{Vitamin, mineral, and additive supplementation per kilogram of feed: iron, 12,500 mg; manganese, 17,500 g; zinc, 12,500 g;} copper, 24,950 g; iodine, 300 mg; selenium, 50 mg; vitamin A, 1,500,000 IU; vitamin D3, 500,000 IU; vitamin E, 2,500 IU; vitamin K3, 400 mg; vitamin B1, 350 mg; vitamin B2, 1,000 mg; vitamin B6, 500 mg; vitamin B12, 2,500 µg; niacin, 7,500 mg; choline, 60,400 g; pantothenic acid, 2,750 mg; folic acid, 150 mg; phytase, 125,000 ftu (units of phytase activity); monensin sodium, 25 g; halquinol, 7,500 mg; salinomycin, 15 g.

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for 8 h. After this period, they were selected,

weighed, and transported to the School

Slaugh-terhouse, where they were stunned by

electro-shock, killed by cutting the jugular vein,

scald-ed, pluckscald-ed, and eviscerated.

The abdominal fat removed from the

abdo-men and gizzard was weighed immediately after

evisceration using a precision digital scale (0.01

g). The eviscerated carcass (with head, feet, and

neck) was cooled for 24 h by air chilling. After

this period, skinless and boneless wing, thigh,

drumstick, and breast cuts were obtained. All

of these cuts, as well as the eviscerated carcass,

were weighed on a precision digital scale (0.01

g). The determinations were made based on the

methodology described [12], with a few

modi-fications. The yield of the carcass, commercial

cuts, and the relative weight of the abdominal fat

were shown relative to the bird BW at slaughter.

The carcass was considered including the head,

feet, and neck.

Table 4. Percentage and calculated composition of the grower II diets1

Item Treatment T3 T4 T5 Ingredient (%) Corn 67.086 65.950 65.924 45% soybean meal 24.958 26.560 26.563

60% corn gluten meal 1.000 1.000 1.000

Soybean oil 3.085 3.128 3.119 Dicalcium phosphate 1.534 1.106 1.106 Limestone 0.766 0.738 0.738 Salt 0.395 0.385 0.385 Sodium bicarbonate 0.015 0.015 0.015 l-Lys HCl 0.362 0.328 0.328 dl-Met 0.263 0.268 0.300 l-Thr 0.116 0.101 0.101 Choline chloride 0.006 0.006 0.006 Supplement2 _0.400 _0.400 _0.400 Antioxidant3 _0.015 _0.015 _0.015 Total 100.00 100.00 100.00 Calculated level ME (kcal/kg) 3,200 3,200 3,200 CP (%) 18.31 18.90 18.92 Calcium (%) 0.775 0.663 0.663 Chlorine (%) 0.271 0.265 0.265 Available phosphorus (%) 0.386 0.309 0.309 Sodium (%) 0.198 0.195 0.195 Potassium (%) 0.663 0.689 0.689 Linoleic acid (%) 3.127 3.140 3.135 Digestible Arg (%) 1.028 1.075 1.075 Digestible Lys (%) 1.048 1.060 1.060 Digestible Met (%) 0.511 0.523 0.555

Digestible Met + Cys (%) 0.755 0.774 0.806

Digestible Thr (%) 0.681 0.689 0.689

Digestible Trp (%) 0.182 0.191 0.191

Digestible Val (%) 0.707 0.734 0.733

1_{T3 = Rostagno [8]; T4 = Rostagno [9]; and T5 = Rostagno [9] modified: 34 to 42 d.}

2_{Vitamin, mineral, and additive supplementation per kilogram of feed: iron, 12,500 mg; manganese, 17,500 g; zinc, 12,500 g;} copper, 24,950 g; iodine, 300 mg; selenium, 50 mg; vitamin A, 1,500,000 IU; vitamin D3, 500,000 IU; vitamin E, 2,500 IU; vitamin K3, 400 mg; vitamin B1, 350 mg; vitamin B2, 1,000 mg; vitamin B6, 500 mg; vitamin B12, 2,500 µg; niacin, 7,500 mg; choline, 60,400 g; pantothenic acid, 2,750 mg; folic acid, 150 mg; phytase, 125,000 ftu (units of phytase activity); monensin sodium, 25 g; halquinol, 7,500 mg; salinomycin, 15 g.

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Statistical and Economic Analysis

The performance and carcass data were

submitted to analysis using the SAS statistical

variance software [13]. To compare treatment

means, the Tukey test at 5% probability was

used.

The average diet cost (

DC

) and the gross

trade margin (

GM

) were determined for the

economic analysis [14]. The DC was calculated

Table 5. Percentage and calculated composition of finisher diets1

60% corn gluten meal 1.000 6.899 1.000 1.000 1.000

Soybean oil 2.136 2.965 3.598 3.471 3.450 Dicalcium phosphate 1.733 1.113 1.448 0.996 0.997 Limestone 0.856 4.028 0.743 0.699 0.699 Salt 0.352 0.209 0.382 0.375 0.375 Sodium bicarbonate 0.015 0.015 0.015 0.015 0.015 l-Lys HCl 0.266 0.244 0.371 0.330 0.332 dl-Met 0.230 — 0.253 0.247 0.279 l-Thr — 0.114 0.118 0.097 0.097 l-Trp — — — 0.003 0.003 Choline chloride 0.018 0.018 0.018 0.018 0.018 Supplement2 _0.400 _0.400 _0.400 _0.400 _0.400 Antioxidant3 _0.015 _0.015 _0.015 _0.015 _0.015 Total 100.00 100.00 100.00 100.00 100.00 Calculated level ME (kcal/kg) 3,176 3,200 3,250 3,250 3,250 CP (%) 17.00 18.00 17.67 18.00 18.00 Calcium (%) 0.850 1.901 0.740 0.614 0.614 Chlorine (%) 0.248 0.160 0.264 0.260 0.260 Available phosphorus (%) 0.420 0.300 0.368 0.286 0.286 Sodium (%) 0.180 0.120 0.192 0.190 0.190 Potassium (%) 0.616 0.531 0.636 0.652 0.651 Linoleic acid (%) 2.671 3.003 3.416 3.350 3.339 Total Arg (%) 1.009 0.834 — — — Total Lys (%) — — — — — Total Met (%) 0.506 0.336 — — —

Total Met + Cys (%) — 0.650 — — —

Digestible Thr (%) — — 0.660 0.654 0.654

Digestible Trp (%) — — 0.173 0.181 0.181

Digestible Val (%) — — 0.680 0.696 0.696

1_{T1 = Cobb Vantress [10]; T2 = NRC [7]; T3 = Rostagno [8]; T4 = Rostagno [9]; and T5 = Rostagno [9] modified (43 to 46 d).} 2_{Vitamin and mineral supplement per kilogram of feed: iron, 12,500 g; manganese, 17,500 g; zinc, 12,500 g; copper, 24,950} g; iodine, 300 mg; selenium, 50 mg; vitamin A, 1,750,000 IU; vitamin D3, 550,000 IU; vitamin E, 2,750 IU; vitamin K, 400 mg; vitamin B1, 500 mg; vitamin B2, 1,250 mg; vitamin B6, 750 mg; vitamin B12, 3,000 µg; niacin, 8,750 mg; choline, 82,000 g; pantothenic acid, 3,250 mg; folic acid, 200 mg; phytase, 125,000 ftu (units of phytase activity); monensin sodium, 25 g; halquinol, 7,500 mg.

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using the cost of the diet and feed

consump-tion for each feeding phase, in which the price

of each treatment was considered in accordance

with nutrient density. The average prices per

ki-logram of ingredient used in the feed and of the

chicken were surveyed on the Brazilian market

in January 2012 and are shown in Table 6.

After the determination of the DC, the GM

was calculated as described in the following

for-mula:

GM

GPT

CRT

PC

CD

i i i i

=

×

,

where PC is the average price of a kilogram of

live chicken (determined at $1.079/kg), CD

i

is

the cost of 1 kg of the diet (in dollars) consumed

by chickens of the experimental unit

i

, GPT

i

is

the total WG from birds of the unit

i

, and CRT

i

is

the total FI by those birds. The latter 2 variables

were determined considering the experimental

period of 1 to 46 d of age of the broilers.

Af-ter the GM calculations were made, the results

were submitted to analysis using SAS [13]. To

compare treatment means, the Tukey test at 5%

probability was used.

RESULTS AND DISCUSSION

Performance

The performance characteristic results

corre-sponding to 1 to 46 d of age of male broilers are

shown in Table 7. No difference (

P

< 0.05) in

this period (full experimental period) was noted

for BW, WG, FI, FC, V, and PEI. The MEC was

similar for treatments T1, T3, and T5, but was

higher for T2 than T1 and T4. The CC was

high-er for T2 than othhigh-er treatments.

Nutrient content among the experimental

di-ets varied mainly with regard to energy, gross

protein, and amino acids. It should be kept in

mind that the T2 diet, following the NRC

recom-mendations [7], is based entirely on total amino

acids. Many authors have stated the importance

of formulating feed based on the ideal protein in

digestible amino acids. Toledo et al. [15] found

that diets formulated based on ideal protein with

synthetic amino acids inclusion promotes higher

economic returns.

Dozier et al. [16] found an increase of 162 and

150% in WG of Ross male and female broilers

compared with the gain estimated by the NRC

Table 6. Price of the ingredients used in the feed formulation in January 2012

Ingredient kilogram ($)Price per

Corn 0.309

45% soybean meal 0.421

60% corn gluten meal 1.461

Soybean oil 1.404 Dicalcium phosphate 1.208 Limestone 0.169 Salt 0.393 Sodium bicarbonate 1.124 l-Lys HCl 4.831 dl-Met 10.000 l-Thr 6.292 l-Trp 19.663 Choline chloride 2.809 Starter premix 4.326 Growth premix 3.567 Finisher premix 3.006 Antioxidant 6.742

Table 7. Performance characteristics from 1 to 46 d of age of male broilers

Item Treatment1 CV (%) T1 T2 T3 T4 T5 BW (g) 3,013 3,080 3,116 3,071 3,113 3.63 Weight gain (g) 2,968 3,036 3,071 3,027 3,068 3.69 Feed consumption (g) 5,064 5,143 5,172 5,017 5,136 2.93 Feed conversion 1.72 1.70 1.70 1.68 1.68 1.88 Viability (%) 97.50 95.43 95.42 94.58 97.08 3.11

Productive efficiency index 366.01 370.81 374.75 369.58 384.85 6.28

Energy consumption (kcal) 15,755b _16,456a _16,079ab _15,597b _15,969ab _2.92 Calorie conversion (kcal/kg of weight gain) 5.31b _5.42a _5.24bc _5.16c _5.21bc _1.47 a–c_{Means followed by a same letter do not differ from each other at 5% probability by the Tukey test.}

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[7]. The authors believe that the growth rate

in-crease among modern strains is accompanied by

an increase in the digestible Lys requirement to

allow the genetic gain to be expressed.

Accord-ing to the NRC recommendations [7], the total

Lys requirement in the starter stage is 1.10%,

decreasing to 1.00% in the grower diet (21–42

d) and to 0.85% in the finisher stage (42–49 d),

a reduction that seems to be very sharp and that

several authors have sought to question.

Braga and Baião [17], Mendes et al. [18],

and Duarte et al. [19] who, when assessing

di-ets with different energy levels in the finisher

stage, noted that the higher energy level tended

to result in a better FCR. However, Lima et al.

[20] observed that the FCR, both of the males

and of the females, from 1 to 40 and 1 to 45

d of age was not affected (

P

> 0.05) by energy

and amino acid levels. As the amino acid

con-tent is concerned (Lys), Kidd et al. [21] noted an

improved FC when they provided higher amino

acid levels.

As energy consumption in the total rearing

period (1–46 d) is concerned, it was noted that

the treatment that followed the NRC

recommen-dations (T2) [7], with feed with higher energy

levels, had higher energy consumption,

corrobo-rating the proposal made by Oliveira Neto et al.

[22], Leandro et al. [23], and Araújo [4]. Pesti

and Miller [24] justified the increased

consump-tion of energy because the lower food intake,

according to the increase of the energy in the

feed, does not suffice to keep energy

consump-tion constant.

With regard to caloric conversion, it was

noted that T2 also showed a higher value in

the same period, unlike the findings of Araújo

[4], who observed that the higher MEC did not

provide a linear improvement in CC. Dozier

et al. [25], although not reporting a significant

improvement in WG and a difference in MEC,

noted a linear improvement in CC with the

in-crease of the diet EMEn using a mixed-age flock

(30–59 d). Reginatto et al. [26] also reported

that low-energy diets were inferior to

high-ener-gy ones with respect to CC (

P

< 0.01), and more

energy was consumed per weight gain unit for

males aged 1 to 21 and 22 to 40 d. Those authors

believe this is likely due to the greater weight

gain of the birds fed high-energy diets.

Carcass Characteristics

The carcass characteristic outcomes are

pre-sented in Table 8 for male broilers at 46 d of

age. Regarding carcass characteristics at 46 d of

age, only the breast, drumstick, and abdominal

fat yield variables (%) showed significant

dif-ferences (

P

< 0.05).

The T2 diet resulted in the worst results for

breast yield. This lower yield can be explained

by the amount of Lys used in this feed, which

was lower compared with the other treatments.

The T2 recommendations are based on total

lev-els, unlike the Cobb Vantress manual [10] and

Rostagno [8, 9] treatments (T1, T3, T4, and T5),

the recommendations of which are based on

di-gestible levels. When working with strains

des-tined to cuts, with breast meat production as the

main objective, Lys is the main nutrient to be

considered [27]. The nearly exclusive use of Lys

to increase body protein [28] causes the amount

of meat on the carcass to increase in accordance

with the dietary level of this amino acid,

provid-Table 8. Yield (%) of the carcass, breast, drumsticks, thighs, wings, and abdominal fat of male broilers at 46 d of age Item (%) Treatment1 CV (%) T1 T2 T3 T4 T5 Carcass 81.63 81.15 81.88 81.48 81.90 0.83 Breast 29.01a _26.91b _28.71a _28.58a _29.09a _3.48 Drumstick 12.27 12.27 12.52 12.38 12.02 3.80 Thigh 16.74b _17.46a _16.80ab _17.29ab _16.91ab _2.88 Wing 9.69 9.87 9.63 9.63 9.63 2.41 Abdominal fat 2.30a _1.99b _1.84b _1.78b _1.97b _10.19

a,b_{Means followed by a same letter do not differ from each other at 5% probability by the Tukey test.}

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ed this increase is accompanied by other amino

acids.

Almeida et al. [29] concluded that the

high-er level of Lys had no effect on the yield and

on the quality of the breast meat. According to

Trindade Neto et al. [6], the level proposed by

the NRC [7] does not meet the demands of the

strains currently found on the market, as higher

levels of Lys improve the breast meat yield in the

finishing stage. Those same authors recommend

that the level of digestible Lys for male broilers

37 to 49 d of age should be no less than 1.10%.

According to Lima et al. [20], when assessing

the levels of Lys and Met + Cys (standard or

10% above the recommended levels), the

high-est breast yield (

P

< 0.05) was achieved when

birds received the highest level of amino acids,

which is in agreement with reports of Café et al.

[30] and Wijtten et al. [31] that the higher levels

of Thr and Lys increase breast meat yield.

How-ever, Stringhini et al. [32], Langhout and Wittjen

[33], and Kidd et al. [21] found no influence of

the amino acid level on breast meat yield in

ei-ther males or females.

Therefore, the birds’ daily amino acid

re-quirements must be met to ensure maximum

protein deposition and minimum fat deposition

on the carcass. Both the lack and the excess of

amino acids, however, may limit lean tissue

growth, increasing the amount of fat, as energy

may be derived from protein deamination. Thus,

excess CP, without the ideal balance of amino

acids, can provide for increased fat deposition

[34].

When analyzing the percentage of abdominal

fat, T1 resulted in the highest value. The same

result was reported by Graña [35], who stated

that diets low in protein (17.5% CP) caused a

significant increase (

P

< 0.05) in abdominal

fat, both in weight and percentage. A possible

explanation for this is related to energy-protein

balance. Feed with low protein and digestible

amino acid levels caused less energy

expendi-ture to metabolize the nitrogen, thereby

enhanc-ing energy retention by the bird and increasenhanc-ing

carcass fat, as indicated by Aftab et al. [36]. The

results agree with those obtained by Costa et al.

[37] and da Silva [38].

When T4 and T5 were analyzed separately,

the additional levels of Met in the feed did not

influence (

P

< 0.05) the carcass, breast, thigh,

drumstick, wing, and abdominal fat yields.

These results are similar to the findings of

Whitaker et al. [39].

With respect to drumstick yield, T2 attained

the highest results. Mendes et al. [18] observed

the worst thigh and drumstick yield when lower

levels of amino acids were provided. However,

Lima et al. [20] found no effect of the levels of

energy and amino acids on thigh and drumstick

yield in either males or females.

Economic analysis

Average DC and GM are presented in Table

9, in accordance with the nutritional programs.

By observing the DC, it was noted that the diet

that followed the Cobb Vantress

recommenda-tions (T1) [10] was the one with the lowest

aver-age cost. For GM, when undertaking the

statisti-cal analysis (

P

< 0.05) according to the results

that were obtained, the treatment that followed

the recommendations provided in the Cobb

Vantress manual (T1) [10] resulted in the higher

GM, unlike the treatment that followed the

rec-ommendations of the NRC (T2) [7], which

re-sulted in the lower marketing GM.

As previously mentioned, nutrient content

among the experimental diets varied mainly

with regard to energy, gross protein, and amino

acids. The provision of these essential nutrients

in poultry diets plays an important role in

deter-mining broiler production cost, unlike vitamins

and minerals, which are provided as

supple-ments for a minimum requirement [5]. In our

study, it was possible to observe that diets that

were in accordance with NRC (T2) [7] used

high levels of energy and protein in their

compo-sition, unlike diets that followed the Cobb

rec-ommendations (T1) [10]. This caused the cost

of the former diets to be higher and, thus, was

reflected in the GM.

CONCLUSIONS AND APPLICATIONS

1. For performance characteristics, MEC

was similar for T1, T3, and T5, but was

higher for T2 than T1 and T4. The CC

was higher for T2 than other treatments,

and no differences for other performance

characteristics were observed.

2. Regarding the economic analysis, we

concluded that the nutritional program

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based on the Cobb Vantress

recommen-dations resulted in the higher trade GM

($0.821), whereas NRC

recommenda-tions were lower ($0.762).

3. Therefore, the nutrient

recommenda-tions contained in the Cobb Vantress

manual should be used as a means to

achieve greater profitability in broiler

production.

REFERENCES AND NOTES

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4. Araújo, R. B. 2010. Desenvolvimento de modelos matemáticos envolvendo níveis nutricionais, desempenho e rendimento de carcaça para otimização de resultados econômicos de frangos de corte. MS. Diss. Univ. São Paulo, Pirassununga, Brazil.

5. Araújo, L. F., O. M. Junqueira, and C. S. S. Araújo. 2002. Diferentes critérios de formulação de rações para fran-gos de corte no período de 1 a 21 dias de idade. Braz. J. Poult. Sci. 4:195–202.

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Table 9. Average diet cost (DC) and gross marketing margin (GM) based on nutritional feedings

Item Treatment1 CV (%) T1 T2 T3 T4 T5 46 d of age DC ($/kg) 0.433 0.470 0.458 0.456 0.459 — GM ($) 0.821a _0.762d _0.785c _0.802b _0.789bc _1.460

a–d_{Means followed by a same letter do not differ from each other at 5% probability by the Tukey Test.}

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