The effects of enzyme combinations in diets for commercial laying hens need further clarification. The goal of this study was to determine if the type of protease used in diets supplemented with phytase affects performance, nutrient intake, egg quality or intestinal mucosa morphometry of laying hens during peak egg production. Seven hundred and eighty hens (25-week-old Hy-Line W36 hens) were assigned to a completely randomized design composed of five treatments/diets with 12 replicates of 13 birds each. The five treatments were: 1) positive control: diet formulated according to the Hy-Line nutritional recommendations, without proteases , 2) negative control A: positive control diet reduced in energy, protein and amino acids according to protease A matrix, without protease supplementation, 3) negative control B: positive control diet reduced in energy, protein and amino acids according to protease B matrix, without protease supplementation, 4) negative control A plus protease A, 5) negative control B plus protease B. There was no effect of the treatments (P > 0.05) on egg production, egg mass or feed conversion; however, the nutritional restriction imposed by the negative controls reduced egg weight (negative control A, P=0.02), albumen height (P < 0.01) and the Haugh unit (P < 0.01). Protease supplementation reduced the calculated intake of protein and amino acids compared to the positive control; nevertheless, protease A was able to maintain egg weight, albumen height and the Haugh unit at the same levels as that obtained with the positive control hens. The intestinal mucosa responded to treatment only at the jejunum (P < 0.01), but the negative controls did not modify villus height or crypt depth compared to the positive control. However, crypt depth of protease B hens was higher than that of the positive control hens. In conclusion, when included in diets supplemented with phytase, the type of protease affects performance, nutrient intake, egg quality and intestinal mucosa morphometry of laying hens during peak egg production. Key words: Amino acid. Egg production. Egg quality. Enzyme. Nutritional restriction. ResumoOs efeitos da utilização em conjunto de enzimas exógenas para aves de postura precisam ser mais explorados na literatura. No intuito de determinar se o tipo de protease, em dietas suplementadas com fitase, interfere no desempenho, qualidade do ovo, ingestão de nutrientes e morfometria da mucosa intestinal de galinhas em pico de postura, 780 galinhas Hy-Line W36 de 25 semanas foram distribuídas em um delineamento inteiramente casualizado composto por cinco tratamentos/dietas com 12 repetições de 13 aves cada. Os cinco tratamentos foram: 1) controle positivo: dieta formulada de acordo com as recomendações nutricionais da Hy-Line, sem proteases, 2) controle negativo A: dieta controle positivo reduzida em energia, proteína e aminoácidos conforme a matriz nutricional da protease A, sem proteases, 3) controle negativo B: dieta controle positivo reduzida em energia, proteína e aminoácidos confor...
machos da linhagem Cobb, criados em sistema intensivo com fornecimento das dietas a partir da fase inicial até a terminação, com abate aos 42 dias. O delineamento foi inteiramente casualizado (DIC) com cinco tratamentos e sete repetições (5 x 7), sendo cada parcela experimental constituída por três aves.Os tratamentos foram os seguintes: T1 -ração basal sem adição de glicerina; T2 -30 g/kg de adição de glicerina; T3 -60 g/kg de adição de glicerina; T4 -90 g/kg de adição de glicerina e T5 -120 g/kg de adição de glicerina. Os resultados mostraram efeito dos níveis de glicerina sobre os parâmetros de carcaça (Peso ao abate, Rendimento de carcaça e do Peito, Peso das Pernas e Asas). Para a cor da carne do peito, ocorreu aumento dos teores de vermelho e alteração no ângulo de tonalidade da cor. Não foram observadas alterações em relação à perda de peso por cozimento, pH final e maciez em ambos os cortes. A glicerina bruta não promoveu alteração nos valores de composição nutricional na carne de frango independente do nível de utilização e do corte.De forma geral, a glicerina bruta na alimentação de frangos apesar de afetar os parâmetros de carcaça, destaca-se como um ingrediente de potencial uso devido às reduzidas alterações observado em relação à qualidade de carne.
The physiological responses of xylose-grown Debaryomyces hansenii were studied under different nutritive stress conditions using continuous cultivation at a constant dilution rate of 0.055 h 3I . Metabolic steady-state data were obtained for xylose, ammonium, potassium, phosphate and oxygen limitation. For xylose and potassium limitation, fully oxidative metabolism occurred leading to the production of biomass and CO P as the only metabolic products. However, potassium-limiting cultivation was the most severe nutritional stress of all tested, exhibiting the highest xylose and O P specific consumption rates along with the lowest biomass yield, 0.22 g g 3I xylose. It is suggested that carbon was mainly channelled to meet the cellular energy requirements for potassium uptake. For the other limiting nutritional conditions increasing amounts of extracellular xylitol were found for ammonium, phosphate and oxygen limitation. Although xylitol excretion is not significant for ammonium limitation, the same is not true for phosphate limitation where the xylitol productivity reached 0.10 g l 3I h 3I , about half of that found under oxygen-limiting conditions, 0.21 g l 3I h 3I . This work is the first evidence that xylitol production by D. hansenii might not only be a consequence of a redox imbalance usually attained under semi-aerobic conditions, but additional physiological mechanisms must be involved, especially under phosphate limitation. Cell yields changed drastically as a function of the limiting nutrient, being 0.22, 0.29, and 0.39 g g 3I xylose for potassium, oxygen and phosphate limitation, respectively, and are a good indicator of the severity of nutritive stress. z
The physiological responses of xylose‐grown Debaryomyces hansenii were studied under different nutritive stress conditions using continuous cultivation at a constant dilution rate of 0.055 h−1. Metabolic steady‐state data were obtained for xylose, ammonium, potassium, phosphate and oxygen limitation. For xylose and potassium limitation, fully oxidative metabolism occurred leading to the production of biomass and CO2 as the only metabolic products. However, potassium‐limiting cultivation was the most severe nutritional stress of all tested, exhibiting the highest xylose and O2 specific consumption rates along with the lowest biomass yield, 0.22 g g−1 xylose. It is suggested that carbon was mainly channelled to meet the cellular energy requirements for potassium uptake. For the other limiting nutritional conditions increasing amounts of extracellular xylitol were found for ammonium, phosphate and oxygen limitation. Although xylitol excretion is not significant for ammonium limitation, the same is not true for phosphate limitation where the xylitol productivity reached 0.10 g l−1 h−1, about half of that found under oxygen‐limiting conditions, 0.21 g l−1 h−1. This work is the first evidence that xylitol production by D. hansenii might not only be a consequence of a redox imbalance usually attained under semi‐aerobic conditions, but additional physiological mechanisms must be involved, especially under phosphate limitation. Cell yields changed drastically as a function of the limiting nutrient, being 0.22, 0.29, and 0.39 g g−1 xylose for potassium, oxygen and phosphate limitation, respectively, and are a good indicator of the severity of nutritive stress.
The aim of this study was to compare mathematical models describing growth curves of white-egg layers at different population densities. To fit the models, 4,000 growing white-egg layers were utilized. The experimental design was completely randomized, with population densities of 71, 68, 65, 62, and 59 birds per cage in the starter phase and 19, 17, 15, 13, and 11 birds per cage in the grower phase, with 10 replicates each. Birds were weighed weekly to determine the average body weight and the weight gain. Gompertz and Logistic models were utilized to estimate their growth. The data analysis was carried out using the PROC NLMIXED procedure of the SAS ® statistical computer software to estimate the parameters of the equation because mixed models were employed. The mean squared error, the coefficient of determination, and Akaike's information criterion were used to evaluate the quality of fit of the models. The studied models converged for the description of the growth of the birds at the different densities studied, showing that they were appropriate for estimating the growth of whiteegg layers housed at different population densities. The Gompertz model showed a better fit than the Logistic model. Key words: Gompertz. Performance. Poultry. ResumoEsta pesquisa teve por objetivo comparar modelos matemáticos para descrever curva de crescimento de poedeiras leves em diferentes densidades populacional, por meio de equações de modelos de crescimento. Para o ajuste dos modelos foram utilizadas 4000 poedeiras leves em crescimento. O delineamento utilizado foi o inteiramente casualizado nas densidades populacional de 71, 68, 65, 62 e 59 aves por gaiola na fase de cria e de 19, 17, 15, 13 e 11 aves por gaiola na fase de recria, com dez repetições cada. Semanalmente, as aves foram pesadas para determinação do peso corporal médio e o ganho de peso.
This study aimed to evaluate the effect of different rearing densities during brooding (0 to 2 weeks) and growth (3 to 15 weeks) on performance and egg quality of laying hens (Hy-line W-36) during production phase (18 to 42 weeks). In the brooding phase, a total of 3250 day-old chicks were allocated in wire cages, distributed in a completely randomized design composed of 5 treatments (63.57; 66.38; 69.44; 72.80 and 76.50 cm²/bird) with 10 replications each. At the beginning of the growth phase, floor space in each treatment was increased. Therefore, a total of 750 birds were selected from the original treatments, which represented 237.57, 265.52, 300.92, 347.22, and 410.35 cm²/bird. At the end of the growing phase, 390 pullets were transferred to production facilities and distributed, according to their original treatment, in conventional cages with 430.76 cm²/bird (13 birds/cage). For this phase, only 6 replications per treatment were adopted. Experimental data were subjected to analysis of variance and, in the case of significant differences, means were analyzed using polynomial regression test. Body weight, weight gain and uniformity were compared during the brooding and growth phases. First-egg weight, age at first egg, age at 50% daily production, weights of egg, albumen, yolk and shell, egg mass, yolk diameter, yolk height, yolk index, albumen height, percentages of shell, albumen and yolk, shell thickness, Haugh unit, and egg specific gravity were analyzed during the production stage. In conclusion, raising pullets on 63.57 cm2/bird (71 birds/cage) does not affect chicks’ performance during the brooding phase. However, for the growth phase, the recommendation is to provide 410.35 cm2/bird, which corresponded to 11 birds/cage in this research. For the production period, the recommendation is to utilize pullets raised on 265.52 cm2/bird, which corresponded to 17 birds/cage on this research.
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