The intensification of livestock have increased the emission of pollutants to the environment, leading to a growing interest in seeking strategies that minimise these emissions. Studies have shown that it is possible to manipulate diets by reducing CP levels and thus reducing nitrogen (N) excretion, without compromising performance. However, there is no knowledge of any study that has focused on reducing N excretion and relating this reduction to individual amino acids. This study investigated the effect of dietary methionine + cysteine (MC) and threonine (THR), the two most limiting amino acids for broiler production, on nitrogen excretion (NE) and nitrogen deposition (ND) and determined the efficiency of utilisation of both amino acids for protein deposition. Six trials were conducted to measure the NE and ND in broiler chickens during three rearing phases in response to dietary amino acid. The efficiency of utilisation of the amino acids was calculated by linear regression of body protein deposition and the amino acid intake. Despite the differences between sexes and phases, the efficiency of utilisation was the same, being 0.60 and 0.59 for MC and THR, respectively. The rate of NE behaved exponentially, increasing with amino acid intake, and can exceed 50% of N intake, being higher than ND. On average, for a reduction in intake of each unit of MC or THR (mg) there is a reduction of 0.5% of NE. Although this reduction seems low, considering that it corresponds to changes in one amino acid only, the impact on a large scale would be significant. Knowledge of how animals respond to NE and ND/protein deposition according to amino acid dietary content may represent new efforts towards reducing the impact on environment.Keywords: amino acids, efficiency of utilisation, environmental pollution, nutrition, poultry ImplicationsThis study shows the effect of amino acids on nitrogen excretion and deposition and on their efficiency of utilisation for protein deposition by broilers. The nitrogen originating from the poultry is an environmental pollutant. Provision of higher amounts of amino acids, besides not increasing protein deposition, also causes increased nitrogen excretion. Meeting animal's amino acids requirements, provides greater efficiency of utilisation of these amino acids, without affecting protein deposition in the animals, and thus reduces nitrogen excretion. In this way, the management of amino acids in broilers diets may allow new efforts to reduce the impact of intensification of livestock. IntroductionThe intensification of livestock have significantly increased the emission of pollutants to the environment, leading to a growing interest in seeking alternatives that minimise these emissions. The European Union has already implemented laws regulating environmental pollution, especially in regard to the emission of nitrogen (N) compounds, considered to be a critical pollutants affecting life on earth (European Commission, 2007). N compounds are responsible for pollution of groundwater due to nitrate lea...

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Na evolução da avicultura, diversas mudanças no manejo, nutrição, genética e ambiente puderam ser observadas ao longo dos anos. O perfil do consumidor de produtos avícolas mudou e estão cada vez mais estão conscientes da necessidade da adoção das práticas de bem-estar na produção de aves. Assim, objetiva-se com esta revisão bibliográfica evidenciar o atual cenário dos principais países produtores avícolas, destacando legislações e recomendações para criação que recaem sobre o bem-estar. Os modelos intensivos de produção causam alterações nos comportamentos inerentes à espécie. Essa situação ocorre devido à vivência em um ambiente estressante, com alta taxa de lotação ao se tratar de aves de corte ou alojamento em gaiolas durante todo o período produtivo das aves de postura. Sob ponto de vista prático, o bem-estar positivo pode ser obtido através da disposição dos animais em um ambiente adequado para sua criação, permitindo expressar o máximo de comportamentos e aspectos naturais. A percepção por parte dos consumidores da senciência dos animais, impulsionou o mercado a realizar mudanças no sistema produtivo, além disso, a obrigatoriedade de atender as legislações internacionais e nacionais foram funda-mentais para melhora no bem-estar na avicultura, já que determinam padrões essenciais para a melhora da qualidade de vida destes animais em confinamento.

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The trial was conducted to evaluate the supplementation of E. coli phytase on performance, weight and ash of bones, as well as to determine the bioavailability of P and cost/benefit of its use in diets. A total 1,890 Cobb male day old chicks were assigned to six treatments and seven replicates with 45 birds each, distributed in a completely randomized design. The treatments were: Positive Control; Negative Control (NC1)-reduction of 0.06% av P; Negative Control 2 (NC2)-reduction of 0.12% av P; NC2 + Phytase (120 OTU); NC2 + Phytase (180 OTU); NC2 + Phytase (240 OTU), being 1 OTU equivalent to approximately 2 FTU. With different phytase inclusions, it was possible to verify a gradual increase on body weight gain, feed intake, feed conversion ratio, viability and even the bone characteristics of broilers fed diets containing reduction of P. The closest levels to the highest studied (240 OTU) showed the best results. The replacement of dicalcium phosphate by phytase supplementation is economically viable when the

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