Níveis de triptofano digestível para frangos de corte machos nas dietas pré-inicial e inicial

The objective was to determine the digestible tryptophan requirements for male broilers in pre-starter and starter phases. Two experiments using 400 Cobb broilers were performed 200 males in the first experiment for the pre-starter phase (one to seven days old), and 200 males in the second experiment for the starter phase (eight to 21 days old). Chicks were housed in batter boxes made of galvanized steel as an experimental shed. The experiments were performed in a completely randomized design, with four treatments and five replicates, with ten birds each. In both experiments, the tryptophan requirement was determined using diets with different levels of digestible tryptophan. A tryptophan-deficient diet was formulated, as a basal diet, which was supplemented with increased levels of L-tryptophan in order to achieve the desirable digestible tryptophan levels. Treatments consisted of 0.209% (basal diet); 0.223%; 0.235% and 0.248% digestible tryptophan for the pre-starter phase (experiment 1) and 0.187% (basal diet); 0.200%, 0.211% and 0.223% digestible tryptophan for the starter phase (experiment 2). We evaluated feed intake, weight gain and feed conversion, as well as the metabolizability of feed nutrients. The performance and metabolic data were subjected to analysis of variance, and estimates of digestible tryptophan levels were made through polynomial regression models at 5% probability. There was no significant difference between the digestible tryptophan levels in the diet over performance and digestibility in both treatments. It is possible to conclude that the basal diet with 0.209% digestible tryptophan for the pre-starter phase and 0.187% for the starter phase, at a tryptophan: lysine ratio of 16%, as sufficient to meet the broilers requirements.Objetivou-se determinar as exigências de triptofano digestível para frangos de corte machos nas fases pré-inicial e inicial. Foram realizados dois experimentos utilizando 400 frangos de corte da linhagem Cobb, sendo o experimento 1 com 200 machos para a fase pré-inicial (um a sete dias de idade), e o experimento 2 com 200 machos para a fase inicial (oito a 21 dias de idade), alojados em baterias, contendo gaiolas de arame galvanizado, em um galpão experimental. Os experimentos foram realizados em delineamento inteiramente casualizado, divididos em quatro tratamentos, com cinco repetições e dez aves por repetição, sendo que cada repetição compreendia uma unidade experimental. Em ambos os experimentos a exigência de triptofano foi determinada utilizando dietas com diferentes níveis de triptofano digestível. Foi formulada uma ração com deficiência em triptofano, considerada a ração basal, a qual foi suplementada com L-triptofano em substituição ao material inerte com o objetivo de alcançar os níveis de triptofano digestível desejáveis. Os tratamentos consistiram em 0.209% (ração basal); 0.223%; 0.235% e 0.248% de triptofano digestível para a fase pré-inicial (experimento 1) e 0.187% (ração basal); 0.200%; 0.211% e 0.223% de triptofano digestível para a fase inicial (experimento 2). Foram avaliados o consumo de ração, o ganho de peso e a conversão alimentar, bem como foi realizada a avaliação da digestibilidade dos nutrientes das rações. Os dados de desempenho e metabolização dos nutrientes da ração foram submetidos à análise de variância, e as estimativas dos níveis de triptofano digestível foram efetuadas através dos modelos de regressão polinomial, em nível de 5% de probabilidade. Não houve diferença significativa entre os níveis de triptofano digestíveis da ração sobre o desempenho e digestibilidade das dietas em ambas as fases. É possível concluir que a dieta basal com 0.209% de triptofano digestível para a fase pré-inicial e 0.187% para a fase inicial, a uma relação triptofano:lisina de 16%, demonstrou-se suficiente para atender as exigências de frangos de corte machos

Mídia e política no Brasil: textos e agenda de pesquisa Midia and politics in Brazil: texts and research agenda

Um especialista em estudos de comunicação e um cientista político apresentam conjuntamente um panorama da pesquisa sobre as relações entre os meios de comunicação e os processos políticos no Brasil. Uma agenda de pesquisa é proposta e um elenco de textos nessa área é apresentado.<br>A specialist in communication studies and a political scientist present together a panorama of research on the relations between communication midia and political processes in Brazil A research agenda is proposed and a list of texts in this area is presented

Diminishing benefits of urban living for children and adolescents’ growth and development

Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified