ABSTRACT Apparent calcium (Ca) retention and digestibility coefficients are affected by limestone particle size in the diet of laying hens. This study aimed to determine the apparent retention and digestibility coefficients of Ca in limestone of different particle sizes in laying hens. The study comprised 288 Lohmann Brown laying hens (50 weeks of age; 1,964 ± 98 g) distributed in a completely randomized experimental design with a 3 × 2 factorial arrangement [three Ca concentrations (10, 20, and 30 g kg–1) × two limestone particle sizes (480 and 1,978 µm)] with eight repetitions per treatment and six birds per experimental unit. The experiment included five days for adaptation and five days for total excreta collection. All birds were slaughtered at the end of the ten days to collect the ileal contents. The total or ileal Ca content was plotted against the Ca of diets concentration using linear regression analysis. The regression line slope represented the apparent retention (CaR) and digestibility coefficients of Ca (CaD) in limestone. There was interaction between Ca concentration in the diet and limestone granulometry on CaD (p = 0.001) and CaR (p < 0.001). The CaD and CaR of fine- and coarse-grained limestone increased linearly with increasing Ca concentrations in the diet. The apparent digestibility coefficients estimated for laying hens fed with fine-grained and coarse-grained limestone were 0.72 and 0.35, respectively. The apparent retention coefficients estimated for laying hens fed fine-grained and coarse-grained limestone were 0.96 and 0.47, respectively.

ABSTRACT The objective of this study was to determine the energy values and metabolizability of different lipid sources in the diet of Japanese quail at the laying phase. The quail were distributed in a completely randomized design with ten replications of seven poultry per treatment, totaling six treatments: basal feed (control) and basal feed containing 10% soybean oil, corn oil, canola oil, sunflower oil, and poultry fat. The values of nitrogen-corrected apparent metabolizable energy (AMEn) and the metabolizability coefficient (MC%) were evaluated. No significant difference was found between the different lipid sources for AMEn (kcal/kg) and MC (%). The value of metabolizable energy corrected for nitrogen for soybean oil was 8,790 kcal/kg; 8,773 kcal/kg for corn oil; 8,784 kcal/kg for canola oil; 8,788 kcal/kg for sunflower oil; and 8,681 kcal/kg for poultry fat in laying Japanese quail. The digestibility coefficients were 93.88% for soybean oil, 93.53% for corn oil, 93.32% for canola oil, 93.74% for sunflower oil, and 93.06% for poultry fat.

Abstract This study aims to evaluate the residual effect of different lipid sources in the diet of Japanese quails (Coturnix japonica) in the rearing phase on the performance and egg quality in the initial phase of egg-laying. In the first stage, 400 Japanese quails aged 21 days were used, being distributed in a completely randomized experimental design, with five treatments and ten replicates of eight birds/replicate Treatments consisted of basal ration (BR) with 2.5% soybean oil; BR with 2.5% corn oil; BR with 2.5% cottonseed oil; BR with 2.5% sunflower oil; and BR with 2.5% canola oil. At 42 days, maintaining the initial design, all quails received a basal ration with soybean oil, in order to evaluate the residual effect of the previous phase on the performance and egg quality in the initial phase of egg-laying (43 - 84 days). The different lipid sources did not affect the performance of quails in the initial phase of production. For egg quality, yolk height, yolk diameter, yolk index, gravity, and Haugh unit (HU) showed better results in the treatment using sunflower oil. There was a residual effect of the use of lipid sources of vegetable origin in the rearing phase diet of Japanese quails on egg quality traits. Lipid sources from soybean, corn, cottonseed, canola, and sunflower seeds can be used as energy sources in the rearing diet of egg-laying quails for not being harmful to their initial performance. The longevity in egg production of quails fed with different lipid sources in the rearing phase was similar.

Resumo A pesquisa foi conduzida com objetivo de avaliar o efeito residual de diferentes fontes lipídicas na dieta de codornas japonesas (Coturnix japonica) na fase de recria sob o desempenho e a qualidade de ovos na fase inicial de postura. Na primeira etapa foram utilizadas 400 codornas japonesas com idade de 21 dias, as aves foram distribuídas em tratamentos seguindo um delineamento inteiramente casualizado com dez repetições, de oito aves, em cinco tratamentos: ração basal (RB) com 2,5% de óleo de soja, RB com 2,5 % de óleo de milho, RB com 2,5% de óleo algodão, RB com 2,5% de óleo de girassol e RB com 2,5% de óleo de canola. Aos 42 dias mantendo o delineamento inicial, todas aves receberam ração basal com óleo de soja, para que fosse avaliado o efeito residual da fase anterior sobre o desempenho e a qualidade dos ovos na fase inicial de postura (43 - 84 dias). As diferentes fontes lipídicas não afetaram o desempenho das aves na fase inicial de produção. Para a qualidade dos ovos, os parâmetros de altura, diâmetro e índice de gema, gravidade e UH foram melhores no tratamento com utilização de óleo de girassol. Houve efeito residual da utilização de fontes lipídicas de origem vegetal na dieta em fase de recria de codornas japonesas sobre as características da qualidade dos ovos. As fontes lipídicas oriundas das sementes de soja, milho, algodão, canola e girassol podem ser utilizadas como ingredientes energéticos na dieta de recria de codornas poedeiras por nâo serem prejudiciais ao desempenho inicial das aves. A longevidade na produção dos ovos das aves alimentadas com diferentes fontes lipídicas na fase de recria foi semelhante.

ABSTRACT This report examines the effects of calcium anacardate (CA) on the morphology, histology, and proteomics of the testes and epididymal ducts of breeding quail. To that end, 22 140-day-old males were grouped in four treatments, each with different concentrations of CA: 0% (control), 0.25%, 0.50%, and 0.75%. The testicles of the animals were weighed and measured, and proteins from the testicles were separated by 1D SDS-PAGE and analyzed via mass spectrometry. Overall, 35 bands were identified in the testicular tissue gels of European quail. Of these, 13 were significantly different, with treatment 0.75% CA being different from the control in all bands. Significant differences among the mean heights of the seminiferous epithelium and diameters of the epididymal duct were observed. In the control group, the average height of the seminiferous epithelium was 71.2 µm, and in 0.75% CA, it was 45.6 µm. Supplementing feed with CA altered the expression of specific proteins, such as superoxide dismutase and heat shock proteins, of the seminal plasma of quail, in addition to facilitating histological alterations regarding the height of the seminiferous epithelium and the diameter of the epididymal duct, improving the reproductive parameters.

ABSTRACT The objective of this study was to evaluate the effects of dietary supplementation of purified lignin on the performance, relative organ weights, serum metabolites, and gene expression profiles of broiler chickens subjected to cyclic heat stress (HS). At 22 days old, 280 broilers were distributed in a completely randomized design with four treatments, ten repetitions, and seven birds per experimental unit. The birds were subjected to daily cyclic HS. A high temperature of 32±1 °C was maintained for 10 h/day (08:00–18:00 h), while a temperature of 22±1 °C was maintained for the remaining time. Treatments were a basal diet or basal diet with the addition of 5, 10, or 15 g of purified lignin/kg of diet. Data were analyzed using one-way ANOVA and means were compared by Tukey's test at 0.05 significance. There was no effect of lignin supplementation on performance, carcass yield, relative weights of the bursa, spleen, and liver, or serum levels of glucose, triglycerides, uric acid, malondialdehyde, triiodothyronine, or tetraiodothyronine. The abundance of mRNA of heat shock protein 70, nuclear factor-κB, glutathione peroxidase, and Cu,Zn-superoxide dismutase in the liver was similarly unaffected by treatments. Purified lignin supplementation does not improve performance or the antioxidant response of broiler chickens subjected to HS.

ABSTRACT Three experiments were carried out to evaluate the effect of dietary combination of different enzymes (phytase + protease) on performance, metabolizable energy, and amino acid digestibility of broiler chickens fed diets with nutritional reduction. A total of 1,400, 336, and 384 male chickens were distributed in a completely randomized design, in the experiments of performance, metabolism, and digestibility, respectively. Treatments were divided as follows: positive control (PC), negative control - NC1 (PC minus 0.16% Ca, 0.15% available P (aP), and 0.5% crude protein (CP)), NC2 (PC minus 0.16% Ca, 0.15% aP, and 1% CP), NC1 added with phytase deriving from citrobacter and protease deriving from Bacillus licheniformis (CBE), NC1 added with phytase deriving from E. coli and protease deriving from microbial fermentation (SE), NC2 added with CBE, and NC2 added with SE. A protein-free diet was included in the digestibility experiment. The nutritional restriction did not affect feed intake of birds in the first experiment; however, the restriction inhibited body weight gain and feed conversion ratio in all phases. In experiment 2, the nutritional restriction decreased AME and AMEn values, although the addition of phytase and protease in diets improved both parameters, mainly in NC2. Treatment NC2 impaired the standardized digestibility of total essential amino acids of animals subjected to experiment 3, although the addition of enzymes helped to recover the digestibility to levels similar to PC. Supplementation of phytase in association with protease is effective to improve performance, energy metabolism, and standardized amino acid digestibility of broilers fed diets with nutrient restriction.

ABSTRACT This study was conducted to evaluate the effects of dietary supplementation with capsaicinoids on the performance and gene expression of broilers. At 18 days of age, 120 male broilers chickens (Cobb 500) were distributed in a completely randomized design with three treatments, eight replicates, and five birds per experimental unit. The treatments were a basal diet or basal diet with the addition of 1 or 2 mg of capsaicinoids/kg of diet. The birds had free access to water and feed throughout the experimental period (18 to 26 days of age). Broiler performance was evaluated at 26 days of age, and one bird per experimental unit was selected to collect serum and jejunum samples. Jejunum samples were used to analyze the mRNA content. Data were analyzed using one-way ANOVA, and the means were compared with Tukey’s test at a significance of 0.05. There was no effect of capsaicinoid supplementation on performance, serum metabolites, or the expression of glutathione peroxidase mRNA in the jejunum of broilers. However, broilers supplemented with capsaicinoids showed a higher mRNA expression of Cu, Zn-superoxide dismutase and a reduced mRNA expression of nuclear factor-κB in the jejunum. Supplementation with 1 and 2 mg/kg capsaicinoids did not improve the performance of broilers from 18 to 26 days of age but increased the mRNA expression of Cu, Zn-superoxide dismutase and reduced the mRNA expression of nuclear factor-κB in the jejunum of broilers.

ABSTRACT The objective of this study was to evaluate the effects of dietary nucleotide supplementation on growth performance, serum immunoglobulin G (IgG) and uric acid levels, immune-related organs, and intestinal morphometric parameters of broiler chickens under pre- and post-inflammatory challenge with lipopolysaccharide (LPS). Ninety-six seven-day-old male broiler chicks were randomized in a 2×2 factorial design composed of two dietary types (supplemented with 0 and 0.3 g of purified nucleotides/kg of feed) and two inflammatory conditions (with and without LPS administration) with eight replicates per treatment and three birds per cage. The experimental period was divided into two phases: 7-20 days of age (pre-LPS challenge) and 21-35 days of age (post-LPS challenge). Data were analyzed using one-way and two-way ANOVA for the pre- and post-challenge phases, respectively. During the pre-challenge phase, dietary nucleotide supplementation improved body weight (982 vs. 1009 g/bird), daily weight gain (58.1 vs. 60.1 g/bird), feed conversion rate (1.28 vs. 1.25 g/g), and serum concentration of IgG (1.17 vs. 1.76 mg/mL) of broilers. During the post-challenge phase, nucleotide supplementation increased serum IgG of broilers at 28 days of age (3.01 vs. 4.34 mg/mL). For the intestinal morphometric parameters, nucleotide supplementation increased villus height (299.3 vs. 315.6 μm). Dietary nucleotide supplementation improves the performance of broilers from seven to 20 days of age (pre-LPS challenge). However, from 21 to 35 days of age, supplementation of 0.3 g of purified nucleotides/kg of feed, independent of inflammatory challenge, does not contribute to improve performance of broilers. Additionally, nucleotide supplementation increases IgG production and villus height in the jejunum of broilers.

ABSTRACT: This study was undertaken to evaluate the effects of dietary calcium levels and supplementation with organic trace minerals selenium, copper, iron, zinc and manganese on performance, tissue deposition and litter mineral concentration. A total of 2,496 one-day-old male Cobb 500 broilers were randomly assigned to a 3 × 4 factorial experimental design with three levels of dietary Ca [8, 10 and 12 g kg–1, while maintaining the same Ca:nPP (non-phytate phosphorus) ratio (2:1)] and four levels of micromineral supplementation (0.62, 0.72, 0.82 and 0.92 g kg–1). There was a total of 12 treatments, with eight replicates of 26 birds per pen. Micromineral supplementation (MS) was achieved by adding different levels of the product Bioplex TR Se® and Ca supplementation was achieved by adding increasing levels of limestone and dicalcium phosphate. An interaction between Ca and MS levels was observed (p < 0.05) for the parameters of performance, liver Cu concentration, breast Se and Cu concentrations and litter Se, Mn and Zn concentrations. No interactions were observed (p > 0.05) for Ca, P or ash concentrations in the tibia, which were influenced only by dietary Ca levels (p < 0.05). The Ca level of 10 g kg–1 promoted higher Ca and P concentration in the tibia and lower micromineral excretion in the litter. The combination of MS level of 0.82 g kg–1 with Ca level of 10 g kg–1 led to the best BWG response. The supplementation conditions that led to higher micromineral levels in the liver and breast varied for each mineral.

ABSTRACT An experiment was carried out to verify the response to the Ca reduction levels of diets with different vitamin D sources on performance, bone mineral deposition, serum concentrations, digestibility, carcass characteristics, and meat quality of broiler chickens in the period from 1 to 42 days reared in thermoneutral environment. A total of 504 male broilers with one day of age and average weight of 43.27±1.08 g were housed in climatic chambers and distributed in a completely randomized design. The study consisted of a 4 × 2 factorial, with four Ca reduction levels (0, 10, 20, and 30%) and two vitamin D sources (2760 IU of D3 or 25-OH-D3). The performance of animals at 21 and 42 days of age was not affected by Ca reduction by up to 30%, regardless of the vitamin source used. Dietary reduction from 10% decreased serum Ca concentrations. The use of vitamin D3 provided a serum P level greater than the 25-OH-D3. Calcium reduction decreased serum 25-OH-D3 levels. No effect of vitamin source or Ca levels on broiler carcass characteristics was observed at 42 days. The vitamin source did not influence meat quality, while Ca reduction of the diet provided lower losses by thawing and cooking and higher initial pH values. The b* color was reduced in diets with lower Ca levels of the diet. Reducing Ca up to 30% does not affect the performance and carcass characteristics, regardless of the vitamin D source used. The quality of broiler meat is improved with the Ca reduction in the diet, but the vitamin used has no effect on such characteristics. We can conclude, based on the results of performance, blood, and bone, that the performance variables are not adequate to determine the actual requirement of Ca, since as it is a priority to maintain performance, bone mineral mobilization occurs, which may compromise the carcass quality of the birds.

RESUMO Objetivou-se avaliar o conforto térmico, o desempenho e as variáveis fisiológicas de frangos de corte alojados em aviários com e sem pintura de telhados de fibrocimento, no período de 21 a 42 dias de idade. Foi utilizado o delineamento inteiramente casualizado, em arranjo com parcela subdividida, onde as parcelas foram compostas pelos galpões (com e sem pintura de telhado) e as subparcelas os horários de avaliação (6, 9, 12, 15 e 18h) ao longo de 22 dias de coleta de dados, considerados como repetição. Observou-se que a pintura externa do telhado na cor branca, proporcionou melhorias no interior do galpão para a temperatura ambiente (Ta), temperatura de telhado (Tt) e na carga térmica de radiação (CTR). A umidade relativa (UR) e o índice de temperatura de globo negro e umidade (ITGU) variaram apenas em função dos horários de coleta. Não houve efeito da pintura externa do telhado nas variáveis fisiológicas das aves. Os índices de desempenho produtivo e a remuneração financeira por lote foram melhores para o galpão com pintura de telhado. Assim, recomenda-se a pintura externa em telhados de fibrocimento, na cor branca, em aviários localizados em ambientes de clima quente, como a região em estudo.

SUMMARY The objective this study was to evaluate the thermal comfort, performance and the physiological variables of 21-42 day of age broiler chickens housed in aviaries with painted and not painted fiber cement roof. A completely randomized design was used in a split-plot design where the plots were composed of the sheds (painted and not painted roof) and the subplots were the evaluation hours (6h00, 9h00, 12h00, 15h00 and 18h00) for a 22-day data collection, considered as the replicates. It was observed that the external painting in white of the roof provided improvements inside the shed for airtemperature (Ta), roof temperature (Tr) and the thermal load of radiation (TLR). The relative humidity (RH) and the Globe-Temperature-Humidity-Index (GTHI) varied only according to the collection times. The exterior painting of the roof had no effect on the physiological variables of the broilers. Productivity performance indexes and financial compensation per lot were better for the roof painted shed. As a result, fiber cement roof painted in white is recommended in aviaries located in hot climates, such as the region in this study.

RESUMO Foram avaliados o desempenho e a cor da pele de frangos de corte de crescimento lento no período de 30 a 90 dias, alimentados com dietas com diferentes inclusões de bagaço de mandioca e colorífico de urucum. 308 frangos de corte de crescimento lento foram utilizados em um delineamento experimental inteiramente casualizado, em esquema fatorial com tratamento adicional 3 X 2 + 1, sendo três níveis de colorífico de urucum como agente pigmentante (1%, 2% e 3%), dois níveis de bagaço de mandioca (10% e 20%) e um tratamento adicional (dieta de controle), totalizando sete tratamentos, quatro repetições e 11 frangos de corte por unidade experimental. O consumo de ração e a conversão alimentar foram influenciados pelos tratamentos, com interação. O ganho de peso e o peso final foram influenciados pelos tratamentos (p<0,001) e os melhores resultados foram encontrados para a inclusão de 10% de bagaço de mandioca e 2% de colorífico de urucum. Não houve efeito dos tratamento e nenhuma interação sobre o rendimento da carcaça. Os parâmetros de cor L *, a * e b * não foram influenciados pelos tratamentos. É recomendável a inclusão de bagaço de mandioca a 10% e 1% de colorífico de urucum para frangos de crescimento lento de 30 a 90 dias de idade. No entanto, o uso desses ingredientes provou ser economicamente inviável.

SUMMARY The performance and breast skin color of slow-growing broilers from 30 to 90 days old fed diets with different inclusions of cassava bagasse and annatto colorific were evaluated. 308 slow-growing broilers were used in a completely randomized experimental design, in a factorial scheme with an additional treatment 3 X 2 + 1, with three levels of annatto colorific as a pigmentant agent (1%, 2% and 3%), two levels of cassava bagasse (10% and 20%) and an additional treatment (control diet), totaling seven treatments, four replicates and 11 broilers per experimental unit. Feed intake and feed conversion were affected by treatments, with interaction. The weight gain and final weight were influenced by the treatments and the best results were found for the inclusion of 10% cassava bagasse and 2% annatto colorific. There was no effect of treatment and no interaction on carcass yield. The color parameters L*, a* and b* were not influenced by treatments. The inclusion of 10% cassava bagasse and 1% annatto colorific for slow-growing broilers from 30 to 90 days of age is recommended. However, the use of these ingredients proved to be economically unfeasible.

Resumo Objetivou-se determinar a exigência de metionina + cistina total para frangas na fase inicial e verificar seu efeito sobre a fase de postura. Na primeira fase experimental, 720 aves (50% Lohmann LSL e 50% Lohmann Brown) com uma semana de idade foram distribuídas em delineamento experimental inteiramente casualizado, em esquema fatorial 5 x 2 (níveis de met + cis e linhagens), com quatro repetições e 18 aves por repetição. Os níveis de met + cis total estudados foram 0,536; 0,616; 0,696; 0,776; e 0,856 %. Ao atingirem 22 semanas de idade, iniciou-se a segunda fase experimental, sendo utilizadas 240 aves (50% Lohmann LSL e 50% Lohmann Brown) provenientes da primeira fase experimental. A ração fornecida às aves nesta fase foi igual para todos os tratamentos. Na fase de produção avaliaram-se os efeitos residuais das dietas fornecidas no período inicial sobre os parâmetros produtivos. As exigências de metionina + cistina recomendadas para aves leves e semipesadas, no período de 1 a 6 semanas de idade, são de 0,778% de met + cis total (correspondendo a 0,700% de met + cis digestível) e 0,739% de met + cis total (correspondendo a 0,665% de met + cis digestível), respectivamente.

Abstract An experiment was carried out to evaluate the requirement of methionine +cystine for growing pullets at starter phase (1 to 6 weeks old) and its effect on the laying phase. In the first experiment, 720 birds (50% Lohmann LSL and 50% Lohmann Brown) at one week of age were distributed on a completely randomized design, 5 x 2 factorial arrangement (levels of met + cys and strain), with four replications and 18 birds each. The levels of total methionine + cystine studied were 0.536; 0.616; 0.696; 0.776; and 0.856 %. At 22 weeks of age, 240 birds were used for the second experimental phase. The diets given to birds at this phase was the same for all the treatments. In the production phase, the residual effects of the experimental diets provided during the initial phase on the production parameters were evaluated. The level of methionine + cystine recommended for white-egg and brown-egg pullets in the period from 1 to 6 weeks of age are 0.778 % of total methionine + cystine (0.700% met + cis digestible) and 0.739% of total methionine + cystine (0.665% of digestible methionine + cystine), respectively.

Resumo Foi realizado um experimento, utilizando-se o método tradicional de coleta total de excretas, com o objetivo de determinar os valores de energia metabolizável aparente, energia metabolizável aparente corrigida pelo balanço de nitrogênio e composição química de seis alimentos: soja integral desativada com casca, soja integral desativada sem casca, concentrado proteico de soja, farelo de soja extrusada semi-integral, farelo de soja e glúten de trigo. Foram utilizados 252 pintos de corte da linhagem comercial Cobb 500, com 14 dias de idade, distribuídos em delineamento inteiramente casualizado, com sete tratamentos (seis rações testes e uma ração referência), seis repetições e seis aves por unidade experimental. Os cinco dias iniciais foram destinados à adaptação das aves às rações experimentais e os cinco dias finais à coleta total das excretas, realizada duas vezes ao dia. Os valores de energia metabolizável aparente corrigida pelo balanço de nitrogênio na matéria natural determinados em frangos de corte no período de 14 a 24 dias de idade foram os seguintes: soja integral desativada com casca: 2797 kcal/kg; soja integral desativada sem casca: 3012 kcal/kg; concentrado proteico de soja: 2554 kcal/kg; farelo de soja extrusada semi-integral: 2467 kcal/kg; farelo de soja: 2221 kcal/kg; glúten de trigo: 3813 kcal/kg.

Abstract We conducted a biological assay using the traditional method of excreta collection, with the purpose to determine the values of apparent metabolizable energy, apparent metabolizable energy corrected for nitrogen balance, and the chemical composition of six feeds: deactivated whole soybean with shuck; deactivated whole soybean without shuck; soy protein concentrate; extruded semi-whole soybean meal; soybean meal; and wheat gluten. We used 252 chicks of the Cobb 500 commercial lineage, from 14 to 24 days of age, distributed in a completely randomized design, with seven treatments (six test rations and a reference ration) and six repetitions with six birds per experimental unit. The five initial days were destined to the adaptation of the birds to the experimental rations, and the five final days were destined to excreta collection, which was carried out twice a day. The values of apparent metabolizable energy corrected for nitrogen balance, based on natural matter determined in broiler chicken aged from 14 to 24 days old were as follows: deactivated whole soybean with shuck: 2797 kcal/kg; deactivated whole soybean without shuck: 3012 kcal/kg; soy protein concentrate:, 2554 kcal/kg; extruded semi-whole soybean meal: 2467 kcal/kg; soybean meal: 2221 kcal/kg and wheat gluten: 3813 kcal/kg.

RESUMO. Objetivou-se avaliar diferentes níveis de lisina digestível em rações para frangos de corte de diferentes linhagens comerciais na fase de 49 a 56 dias de idade sobre o desempenho e características de carcaça. Foram utilizados 432 frangos de corte machos de 49 dias de idade, com peso médio inicial de 3560±250 g. Utilizou-se o delineamento inteiramente casualizado em arranjo fatorial 3x4, sendo que as aves, oriundas de três linhagens (Cobb 500, Hubbard Flex e Ross 308), foram distribuídas em quatro níveis de lisina digestível (0,800; 0,950; 1,100 e 1,250%), com quatro repetições de 12 aves cada. Avaliou-se o ganho de peso, o consumo de ração, a conversão alimentar, o rendimento de carcaça, o rendimento de peito, o rendimento de carne de peito e o rendimento de coxa e sobrecoxa. Não houve interação entre os níveis de lisina digestível e as linhagens comerciais de frangos de corte. Os diferentes níveis de lisina não influenciaram (p ≥ 0,05) o desempenho e rendimento de carcaça. Existem diferenças significativas entre as linhagens para consumo de ração e características de carcaça. Sendo que a linhagem Cobb 500 teve maior rendimento de peito e carne de peito (p ≤ 0,05), enquanto as linhagens Hubbard Flex e Ross 308 tiveram maior rendimento de coxa e sobrecoxa (p ≤ 0,05).

ABSTRACT. This study aimed to evaluate different digestible lysine levels in diets for broilers chickens from different commercial strains, from 49 to 56 days of age, on performance and carcass characteristics. A total of 432 male broilers from 49 days old were used, with an average weight of 3560±250 g. It was used a completely randomized design in a factorial arrangement 3x4, and the birds, from three strains (Cobb 500, Hubbard Flex and Ross 308) were divided into four levels of digestible lysine (0.800, 0.950, 1.100 and 1.250%), with four replicates of 12 birds each. It was evaluated the weight gain, feed intake, feed conversion ratio, carcass yield, breast yield, breast meat yield and the yield of the thigh and drumstick. There was no interaction between lysine levels and commercial strains of broiler chickens. The different lysine levels did not influence (p ≥ 0.05) performance and carcass yield. There are significant differences between strains for feed intake and carcass characteristics. The Cobb 500 strain had higher breast yield and breast meat (p < 0.05), while the Hubbard Flex and Ross 308 strains had higher yield of the thigh and drumstick (p < 0.05).