Ajuste de modelos de crescimento em frangos de corte

The objective of this work was to investigate adjustments of the Gompertz, Logistic, von Bertalanffy, and Richards growth models, in male and female chickens of the Cobb 500, Ross 308, and Hubbard Flex lines. Initially, 1,800 chickens were randomly housed in 36 pens, with six replicates per lineage and sex, fed ad libitum with feed according to gender, and bred until 56 days of age. Average weekly body weight for each line and sex was used to estimate model parameters using the ordinary least squares, weighted by the inverse variance of the body weight and weighted with a first-order autocorrelated error structure. Weighted models and weighted autocorrelated error models showed different parameter values when compared with the unweighted models, modifying the inflection point of the curve and according to the adjusted coefficient of determination, and the standard deviation of the residue and Akaike information criteria exhibited optimal adjustments. Among the models studied, the Richards and the Gompertz models had the best adjustments in all situations, with more realistic parameter estimates. However, the weighted Richards model, with or without ponderation with the autoregressive first order model AR (1), exhibited the best adjustments in females and males, respectively.O objetivo deste trabalho foi investigar os ajustes dos modelos de crescimento Gompertz, Logístico, von Bertalanffy e Richards em frangos fêmeas e machos das linhagens Cobb 500, Ross 308 e Hubbard Flex. Foram inicialmente utilizados 1.800 frangos, alojados aleatoriamente em 36 unidades experimentais, com seis repetições por linhagem e sexo, alimentados à vontade com ração, de acordo com o gênero, e criados até 56 dias de idade. A partir do peso vivo médio semanal de cada linhagem e sexo, realizou-se a estimação dos parâmetros dos modelos, por meio dos mínimos quadrados ordinários, ponderados pelo inverso da variância do peso e ponderados com estrutura de erros autocorrelacionados de primeira ordem. Modelos ponderados e modelos ponderados com autocorrelação apresentaram valores diferentes dos parâmetros comparados aos modelos não ponderados, mudando o ponto de inflexão da curva e de acordo com o coeficiente de determinação ajustado, e o desvio padrão do resíduo e os critérios de informação de Akaike apresentaram os melhores ajustes. Entre os modelos estudados, os de Richards e Gompertz resultaram nos melhores ajustes em todas as situações, com as estimativas mais reais dos parâmetros. Porém, o modelo ponderado de Richards, com ou sem ponderação com o modelo autorregressivo de primeira ordem AR (1), apresentou os melhores ajustes em fêmeas e machos, respectivamente

Performance, egg quality and nitrogen balance of commercial laying hens fed diets with different levels of crude protein and lysine

O experimento foi conduzido para avaliar os efeitos de rações com diferentes níveis de proteína bruta (PB) e lisina sobre as características de desempenho, a qualidade interna dos ovos e o balanço/retenção do nitrogênio. Foram utilizadas 160 poedeiras Hisex White com 48 semanas de idade, alojadas individualmente em delineamento inteiramente casualizado em esquema fatorial 4 × 2, com quatro níveis de PB (12, 14, 16 e 18%) e dois de lisina (0,85 e 1,00%), totalizando oito rações com cinco repetições de quatro aves. O consumo de proteína bruta, o peso dos ovos, a massa de ovos e a porcentagem de albúmen apresentam resposta linear crescente aos níveis de PB na dieta. O balanço de nitrogênio não é alterado pelos níveis de proteína das rações.The experiment was carried out to evaluate the effects of diets with different levels of crude protein (CP) and lysine (LYS) on characteristics of performance, egg internal quality, and nitrogen balance/retention. It was used 160 Hisex White laying hens at 48 weeks of age, individually accomodated in a complete random design in a 4 × 2 factorial scheme with four levels of crude protein (12, 14, 16 and 18%) and two levels of lysine (0.85 and 1.00%), totalizing eight treatments with five replicates of four birds each. Crude protein intake, egg weight, egg mass and percentage of the albumen show increasing linear response to the levels of crude protein in the diet. Nitrogen balance is not altered by the levels of proteins in the diets.Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES

Performance and egg quality of commercial laying hens fed diets with different levels of methionine and lysine

Foram avaliados os efeitos dos níveis de metionina e lisina sobre o desempenho e a qualidade interna e externa dos ovos de poedeiras comerciais. Foram utilizadas 256 poedeiras Hisex White com 68 semanas de idade, alojadas individualmente em delineamento inteiramente casualizado em arranjo fatorial 4 õ 4, com quatro níveis de lisina (0,482; 0,682; 0,882 e 1,082%) e metionina (0,225; 0,318; 0,411 e 0,505%), totalizando 16 dietas, cada uma com quatro repetições de quatro aves. O desempenho foi avaliado por meio das características consumos de ração, lisina, metionina, proteína bruta e de energia, peso, produção e massa de ovos e conversão alimentar. A qualidade interna dos ovos foi avaliada por meio das características peso e porcentagem de albúmen e gema e pela unidade Haugh. As aves apresentaram máxima produção de ovos quando alimentadas com rações contendo 0,444% de metionina total e 0,872% de lisina total. A classificação dos ovos por tipo e as características de qualidade interna e externa dos ovos não foram influenciadas pelos níveis de metionia e lisina da dieta.This experiment was carried out to evaluate the effects of levels of methionine and lysine on performance and on the internal and external egg quality of commercial laying hens. It was used 256 Hisex White laying hens at 68 weeks of age, which were individually housed in a complete random design in a 4 õ 4 factorial scheme with four levels of lysine (0.482, 0.682, 0.882, and 1.082%) and of methionine (0.225, 0.318, 0.411, and 0.505%) totaling sixteen diets with four replicates with four birds each. Performance was evaluated through the following characteristics: feed intake, consumption of lysine, methionine, crude protein and energy, weight, production and mass of eggs and feed conversion. Internal quality of eggs was evaluated through the characteristics of weight and yolk percentage and by Haugh unit. Birds showed maximal egg production when fed rations with 0.444% of total methionine and 0.872% total lysine. Rating of eggs by their types and internal and external quality of eggs were not influenced by levels of methionine and lysine in the diet

Metabolizable energy values of diets supplemented with xylanase determined with laying hens

The objective of this study was to evaluate the effect of the supplementation of xylanase in diets with reduced energy level on the apparent metabolizable energy corrected for nitrogen, determined with laying hens at 14, 36, 60 and 80 weeks of age. Four digestibility trials were conducted, using 80 Hy-line W36 laying hens aged 14, 36, 60 and 80 weeks of age. Birds were distributed in a completely randomized design in 2 x 2 factorial arrangement (energy level x inclusion of xylanase), totaling four treatments with 10 replicates of two birds each. Treatments were: positive control (balanced diet for their age); positive control + xylanase; negative control (diet with reduction of 100 kcal/kg in the level of metabolizable energy); and negative control + xylanase. Xylanase, produced by microorganism Trichoderma reesei, was added to the diets at 100 g/t (16,000 BXU/kg) for diets fed at 14 weeks and 75 g/t for diets of 36, 60 and 80 weeks (12,000 BXU/kg). The data obtained were subjected to analysis of variance at 5% probability. Supplementation of xylanase promoted higher values for AME (apparent metabolizable energy) and AME(n) (apparent metabolizable energy corrected for nitrogen) determined with 80-week-old laying hens, subjected to diet with energy level according to the nutritional requirements for their age. Supplementation of xylanase increases the matabolizability coefficient of the dietary crude protein and improves the nitrogen retention of laying hens at 14 weeks. In addition, xylanase associated with adequate levels of dietary energy promotes higher values for AME and AME(n) determined with laying hens at 80 weeks of age

Avaliação do desenvolvimento da discondroplasia tibial em frangos de corte submetidos à dieta com 25 hidroxicolecalciferol

Este trabalho teve como objetivo avaliar o desenvolvimento da discondroplasia tibial (DT) em frangos de corte de 1 a 21 dias. Foram utilizados 440 pintinhos machos de um dia, provenientes de matrizes com 60 a 62 semanas de idade, distribuídos em delineamento inteiramente casualisado em esquema fatorial 3x3+2, resultando em 11 tratamentos com quatro repetições de 10 aves cada. Os fatores estudados foram: linhagem da ave (Ross 308, Cobb 500 e Hybro), níveis e fontes de vitamina D (1250UI D3/kg sem 25-(OH)D3; 1250UI D3/kg com 69mg 25-(OH)D3/ton e 3000UI D3/kg com 69mg 25-(OH)D3/ton) e dois tratamentos controles com níveis de cálcio e fósforo com 3000UI D3/kg sem 25-(OH)D3 e 3000UI D3/kg com 69mg 25-(OH)D3/ton de ração. Foram avaliadas características ósseas. No período de 1 a 21 dias, os resultados indicaram que as concentrações de cálcio e fósforo nas tíbias não foram influenciadas pelos tratamentos e que o consumo de ração foi superior para os tratamentos que compõem o fatorial. A resistência óssea também não foi influenciada pelos tratamentos e a análise histológica não evidenciou lesões características de DT. Conclui-se que, nas condições experimentais da presente pesquisa, o desenvolvimento de DT não foi observado.This research was carried out to evaluate the development of tibial dyschondroplasia (TD) in broilers from 1 to 21 days. Four hundred forty day-old male chickens, from broiler breeders aged 60-62 weeks, were randomly distributed in a 3x3+2 factorial arrangement, resulting in 11 treatments with four replicates of 10 birds each. The factors evaluated were: bird strains (Ross 308, Cobb 500, and Hybro), levels and sources of vitamin D (1250UI D3/kg without 25-(OH)D3; 1250UI D3/kg with 69mg 25-(OH)D3/ton, and 3000UI D3/kg with 69mg 25-(OH)D3/ton), and two control treatments containing calcium and phosphorus levels with 3000UI D3/kg without 25-(OH)D3 and 3000UI D3/kg with 69mg 25-(OH)D3/ton of feed. Bone characteristics were evaluated. From 1 to 21 days, the results showed that bone calcium and phosphorus concentrations were not influenced by the treatments, however, feed intake was higher for factorial than control treatments. Bone breaking resistance was not influenced by the treatments and there were no typical lesions of TD. In conclusion, it was not observed TD development in broilers from 1 to 21 days according to experimental procedures of this research