Feeding programs and their effects on broiler performance and economic indexes

Transcription

1 2014 Poultry Science Association, Inc. 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, , 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 experimental design with 5 treatments and 8 replicates with 30 birds per experimental 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 : DESCRIPTION OF PROBLEM The adoption of new technologies in the Brazilian poultry industry has evolved greatly when compared with other agricultural activities, 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 crises 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 indexes, 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 techni- 1 Corresponding author: retrevi@gmail.com

2 2 JAPR: Research Report 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 strategies 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 increase the efficiency and quality of the feed provided to the birds [3]. Those technologies include determining nutrient levels for each stage of development. To have an optimal feed-formulation 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 biological and economic aspects [4]. Different nutritional recommendations coming from various regions of Brazil and from several other countries, distant from the Brazilian climate and productive reality, have also been a problem when establishing the best nutritional recommendation 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 constant 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 broilers most reared by the Brazilian industry. From an applied point of view, this is a good opportunity to compare scientific publications [7 9] with the Cobb Vantress manual [10]. Considering that the nutritional requirements of the current high-yield broiler chicken are different from those raised several years ago and that several 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 Animal 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 g and originating from 43-wk-old commercial breeders. The experiment lasted 46 d. Bird distribution was made based on a completely randomized design, with 5 treatments and 8 replications, totaling 40 experimental 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 relative to Lys (T5) from Rostagno [9]. The feeding stages were set pursuant to each recommendation. Experimental Diets All diets were formulated according to the requirement of each stage and respecting the nutritional 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 (prestarter stage), 8 to 21 (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 leftovers were weighed weekly to monitor bird development. Dead animals were recorded daily. Performance characteristics were calculated weekly as feed intake (FI), BW, weight gain

3 Trevisan et al.: EFFECTS OF FEEDING PROGRAMS 3 Table 1. Percentage and calculated composition of prestarter diets 1 Treatment T1 T3 T4 T5 Ingredient (%) Corn % soybean meal % corn gluten meal Soybean oil Dicalcium phosphate Limestone Salt Sodium bicarbonate l-lys HCl dl-met l-thr Choline chloride Supplement Antioxidant Total Calculated level ME (kcal/kg) 2,988 2,960 2,960 2,960 CP (%) Calcium (%) Chlorine (%) Available phosphorus (%) Sodium (%) Potassium (%) Linoleic acid (%) Total Arg (%) Total Met (%) Total Thr (%) Total Trp (%) Total Val (%) Digestible Arg (%) Digestible Lys (%) Digestible Met (%) Digestible Met + Cys (%) Digestible Thr (%) Digestible Trp (%) Digestible Val (%) 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 D 3, 550,000 IU; vitamin E, 2,750 IU; vitamin K, 400 mg; vitamin B 1, 500 mg; vitamin B 2, 1,250 mg; vitamin B 6, 750 mg; vitamin B 12, 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%. (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 difference between the total feed fed to the birds and the leftovers of each experimental unit divided 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 difference 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-

4 4 JAPR: Research Report Table 2. Percentage and calculated composition of starter diets 1 Treatment T1 T2 T3 T4 T5 Ingredient (%) Corn % soybean meal % corn gluten meal Soybean oil Dicalcium phosphate Limestone Salt Sodium bicarbonate l-lys HCl dl-met l-thr Choline chloride Supplement Antioxidant Total Calculated level ME (kcal/kg) 3,083 3,200 3,050 3,050 3,050 CP (%) Calcium (%) Chlorine (%) Available phosphorus (%) Sodium (%) Potassium (%) Linoleic acid (%) Total Arg (%) Total Lys (%) Total Met (%) Total Met + Cys (%) Total Thr (%) Total Trp (%) Total Val (%) Digestible Arg (%) Digestible Lys (%) Digestible Met (%) Digestible Met + Cys (%) Digestible Thr (%) Digestible Trp (%) Digestible Val (%) 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 D 3, 550,000 IU; vitamin E, 2,750 IU; vitamin K, 400 mg; vitamin B 1, 500 mg; vitamin B 2, 1,250 mg; vitamin B 6, 750 mg; vitamin B 12, 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%. 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 percentage) V = 100% mortality %. The MEC was determined by adding feed consumption in each feeding phase (g/bird) multiplied by the corresponding ME (expressed in kilocalories per bird). Caloric conversion was determined based

5 Trevisan et al.: EFFECTS OF FEEDING PROGRAMS 5 Table 3. Percentage and calculated composition of grower I diets 1 Treatment T1 T2 T3 T4 T5 Ingredient (%) Corn % soybean meal % corn gluten meal Soybean oil Dicalcium phosphate Limestone Salt Sodium bicarbonate l-lys HCl dl-met l-thr Choline chloride Supplement Antioxidant Total Calculated level ME (kcal/kg) 3,176 3,200 3,150 3,150 3,150 CP (%) Calcium (%) Chlorine (%) Available phosphorus (%) Sodium (%) Potassium (%) Linoleic acid (%) Total Arg (%) Total Lys (%) Total Met (%) Total Met + Cys (%) Total Thr (%) Total Trp (%) Total Val (%) Digestible Arg (%) Digestible Lys (%) Digestible Met (%) Digestible Met + Cys (%) Digestible Thr (%) Digestible Trp (%) Digestible Val (%) 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 D 3, 500,000 IU; vitamin E, 2,500 IU; vitamin K 3, 400 mg; vitamin B 1, 350 mg; vitamin B 2, 1,000 mg; vitamin B 6, 500 mg; vitamin B 12, 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. 3 Feedguard: butyl hidroxi toulen (minimum) 3%; ethoxyquin (minimum) 11.3%; terc-butil-hidroquinona (minimum) 1%, citric acid (minimum) 4%. 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, commercial cuts, and relative abdominal fat weight assessments. The birds had fasted from feed

6 6 JAPR: Research Report Table 4. Percentage and calculated composition of the grower II diets 1 Treatment T3 T4 T5 Ingredient (%) Corn % soybean meal % corn gluten meal Soybean oil Dicalcium phosphate Limestone Salt Sodium bicarbonate l-lys HCl dl-met l-thr Choline chloride Supplement Antioxidant Total Calculated level ME (kcal/kg) 3,200 3,200 3,200 CP (%) Calcium (%) Chlorine (%) Available phosphorus (%) Sodium (%) Potassium (%) Linoleic acid (%) Digestible Arg (%) Digestible Lys (%) Digestible Met (%) Digestible Met + Cys (%) Digestible Thr (%) Digestible Trp (%) Digestible Val (%) 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 D 3, 500,000 IU; vitamin E, 2,500 IU; vitamin K 3, 400 mg; vitamin B 1, 350 mg; vitamin B 2, 1,000 mg; vitamin B 6, 500 mg; vitamin B 12, 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. 3 Feedguard: butyl hidroxi toulen (minimum) 3%; ethoxyquin (minimum) 11.3%; terc-butil-hidroquinona (minimum) 1%, citric acid (minimum) 4%. for 8 h. After this period, they were selected, weighed, and transported to the School Slaughterhouse, where they were stunned by electroshock, killed by cutting the jugular vein, scalded, plucked, and eviscerated. The abdominal fat removed from the abdomen 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 modifications. 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.

7 Trevisan et al.: EFFECTS OF FEEDING PROGRAMS 7 Table 5. Percentage and calculated composition of finisher diets 1 Treatment T1 T2 T3 T4 T5 Ingredient (%) Corn % soybean meal % corn gluten meal Soybean oil Dicalcium phosphate Limestone Salt Sodium bicarbonate l-lys HCl dl-met l-thr l-trp Choline chloride Supplement Antioxidant Total Calculated level ME (kcal/kg) 3,176 3,200 3,250 3,250 3,250 CP (%) Calcium (%) Chlorine (%) Available phosphorus (%) Sodium (%) Potassium (%) Linoleic acid (%) Total Arg (%) Total Lys (%) Total Met (%) Total Met + Cys (%) Total Thr (%) Total Trp (%) Total Val (%) Digestible Arg (%) Digestible Lys (%) Digestible Met (%) Digestible Met + Cys (%) Digestible Thr (%) Digestible Trp (%) Digestible Val (%) 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 D 3, 550,000 IU; vitamin E, 2,750 IU; vitamin K, 400 mg; vitamin B 1, 500 mg; vitamin B 2, 1,250 mg; vitamin B 6, 750 mg; vitamin B 12, 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%. 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

8 8 JAPR: Research Report Table 6. Price of the ingredients used in the feed formulation in January 2012 Ingredient using the cost of the diet and feed consumption for each feeding phase, in which the price of each treatment was considered in accordance with nutrient density. The average prices per kilogram 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 formula: GM i GPT i PC =, CRT CD where PC is the average price of a kilogram of live chicken (determined at $1.079/kg), CD i is i Price per kilogram ($) Corn % soybean meal % corn gluten meal Soybean oil Dicalcium phosphate Limestone Salt Sodium bicarbonate l-lys HCl dl-met l-thr l-trp Choline chloride Starter premix Growth premix Finisher premix Antioxidant i 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. After 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 corresponding 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 higher for T2 than other treatments. Nutrient content among the experimental diets varied mainly with regard to energy, gross protein, and amino acids. It should be kept in mind that the T2 diet, following the NRC recommendations [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 7. Performance characteristics from 1 to 46 d of age of male broilers Treatment 1 T1 T2 T3 T4 T5 CV (%) BW (g) 3,013 3,080 3,116 3,071 3, Weight gain (g) 2,968 3,036 3,071 3,027 3, Feed consumption (g) 5,064 5,143 5,172 5,017 5, Feed conversion Viability (%) Productive efficiency index Energy consumption (kcal) 15,755 b 16,456 a 16,079 ab 15,597 b 15,969 ab 2.92 Calorie conversion (kcal/kg of weight gain) 5.31 b 5.42 a 5.24 bc 5.16 c 5.21 bc 1.47 a c Means followed by a same letter do not differ from each other at 5% probability by the Tukey test. 1 T1 = Cobb Vantress [10]; T2 = NRC [7]; T3 = Rostagno [8]; T4 = Rostagno [9]; and T5 = Rostagno [9] modified.

9 Trevisan et al.: EFFECTS OF FEEDING PROGRAMS 9 [7]. The authors believe that the growth rate increase among modern strains is accompanied by an increase in the digestible Lys requirement to allow the genetic gain to be expressed. According 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 diets 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 content 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 recommendations (T2) [7], with feed with higher energy levels, had higher energy consumption, corroborating the proposal made by Oliveira Neto et al. [22], Leandro et al. [23], and Araújo [4]. Pesti and Miller [24] justified the increased consumption of energy because the lower food intake, according to the increase of the energy in the feed, does not suffice to keep energy consumption 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 increase 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-energy 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 presented 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 differences (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 levels, unlike the Cobb Vantress manual [10] and Rostagno [8, 9] treatments (T1, T3, T4, and T5), the recommendations of which are based on digestible levels. When working with strains destined 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 Treatment 1 (%) T1 T2 T3 T4 T5 CV (%) Carcass Breast a b a a a 3.48 Drumstick Thigh b a ab ab ab 2.88 Wing Abdominal fat 2.30 a 1.99 b 1.84 b 1.78 b 1.97 b a,b Means followed by a same letter do not differ from each other at 5% probability by the Tukey test. 1 T1 = Cobb Vantress [10]; T2 = NRC [7]; T3 = Rostagno [8]; T4 = Rostagno [9]; and T5 = Rostagno [9] modified.

10 10 JAPR: Research Report ed this increase is accompanied by other amino acids. Almeida et al. [29] concluded that the higher 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 highest 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. However, 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 either males or females. Therefore, the birds daily amino acid requirements 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 expenditure to metabolize the nitrogen, thereby enhancing energy retention by the bird and increasing 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 recommendations (T1) [10] was the one with the lowest average cost. For GM, when undertaking the statistical 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 recommendations of the NRC (T2) [7], which resulted 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 determining broiler production cost, unlike vitamins and minerals, which are provided as supplements 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 composition, unlike diets that followed the Cobb recommendations (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

11 Trevisan et al.: EFFECTS OF FEEDING PROGRAMS 11 Table 9. Average diet cost (DC) and gross marketing margin (GM) based on nutritional feedings Treatment 1 T1 T2 T3 T4 T5 CV (%) 46 d of age DC ($/kg) GM ($) a d c b bc a d Means followed by a same letter do not differ from each other at 5% probability by the Tukey Test. 1 T1 = Cobb Vantress [10]; T2 = NRC [7]; T3 = Rostagno [8]; T4 = Rostagno [9]; and T5 = Rostagno [9] modified. based on the Cobb Vantress recommendations resulted in the higher trade GM ($0.821), whereas NRC recommendations were lower ($0.762). 3. Therefore, the nutrient recommendations contained in the Cobb Vantress manual should be used as a means to achieve greater profitability in broiler production. REFERENCES AND NOTES 1. Associação Brasileira de Produtores e Exportadores de Frango (ABEF) Accessed Nov ubabef.com.br/files/publicacoes/41c30a0f b f70fae077.pdf. 2. Teixeira, R. B., A. L. C. Paiva, and M. Yamaki Avaliação do índice de eficiência produtiva em três híbridos de frangos de corte. ZOOTEC 2004, 28 a 31 de maio de Brasília, DF, Brazil. Zootec, Brasília, DF, Brazil. 3. Moosavi, M., M. Eslami, and M. Chaji Economic value of diets with different levels of energy and protein with constant ratio on broiler chickens. J. Anim. Vet. Adv. 10: Araújo, R. B 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 Diferentes critérios de formulação de rações para frangos de corte no período de 1 a 21 dias de idade. Braz. J. Poult. Sci. 4: Trindade Neto, M. A., P. Takeara, and A. L. Toledo Níveis de lisina digestível para frangos de corte machos no período de 37 a 49 dias de idade. R. Bras. Zootec. 38: NRC Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC. 8. Rostagno, H. S Tabelas Brasileiras para Aves e Suínos: Composição de Alimentos e Exigências Nutricionais. Universidade Federal de Viçosa, Viçosa, MG, Brazil. 9. Rostagno, H. S Tabelas Brasileiras para Aves e Suínos: Composição de Alimentos e Exigências Nutricionais. 3rd ed. Universidade Federal de Viçosa, Viçosa, MG, Brazil. 10. Cobb Vantress Cobb 500: Suplemento de Crescimento e Nutrição para Frangos de Corte. Cobb Vantress, Siloam Springs, AR. 11. Sakomura, N. K., and H. S. Rostagno Métodos de Pesquisa em Nutrição de Monogástricos. Funep, Jaboticabal, Brazil. 12. Mendes, A. A Efeito de Fatores Genéticos, Nutricionais e de Ambiente Sobre o Rendimento de Carcaça de Frangos de Corte. Tese (Livre Docência), Faculdade de Medicina Veterinária e Zootecnia, Universidade Estadual Paulista, Botucatu, SP, Brazil. 13. SAS Institute SAS User s Guide: Statistics. Version 6. SAS Institute Inc., Cary, NC. 14. Gameiro, A. H Avaliação econômica aplicada à zootecnia: Avanços e desafios. Page 215 in Novos Desafios da Pesquisa em Nutrição e Produção Animal. M. V. Santos, L. F. Prada e Silva, F. P. Rennó, and R. Albuquerque, ed. Editora 5D, Pirassununga, Brazil. 15. Toledo, G. S., J. López, and P. T. Costa Aplicação dos conceitos de proteína bruta e proteína ideal sobre o desempenho de frangos de corte machos e fêmeas criados no inverno. Cienc. Rural 34: Dozier, W. A., A. Corzo, M. T. Kidd, P. B. Tillman, J. P. McMurtry, and S. L. Branton Digestible lysine requirements of male broilers from 28 to 42 days of age. Poult. Sci. 89: Braga, J. P., and N. C. Baião Suplementação lipídica no desempenho de aves em altas temperaturas. Cad. Téc. Vet. Zootec. UFMG 31: Mendes, A. A., J. Moreira, E. G. de Oliveira, E. A. Garcia, M. I. M. de Almeida, and R. G. Garcia Efeito da energia da dieta sobre desempenho, rendimento de carcaça e gordura abdominal de frangos de corte. R. Bras. Zootec. 33: Duarte, K. F., O. M. Junqueira, R. S. Filardi, A. C. de Laurentiz, E. M. Casartelli, V. Assuena, and P. A. P. Ribeiro Efeito de diferentes níveis de energia e de programas de alimentação sobre o desempenho de frangos de corte abatidos tardiamente. R. Bras. Zootec. 35: Lima, L. M. B., L. J. C. Lara, N. C. Baião, S. V. Cançado, B. C. Michell, and F. C. Ferreira Efeitos dos níveis de energia, lisina e metionina + cistina sobre o desempenho e o rendimento de carcaça de frangos de corte. R. Bras. Zootec. 37: Kidd, M. T., A. Corzo, D. Hoehler, E. R. Miller, and W. A. Dozier Broiler responsiveness (Ross 708) to diets varying in amino acid density. Poult. Sci. 84:

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