-The objective of this study was to evaluate the requirement of digestible tryptophan for white laying hens in the production stage fed diets of different digestible tryptophan:digestible lysine ratios, as well as animal performance and histological alterations in their reproductive and digestive systems. A total of 280 white laying hens at 29 weeks of age were distributed in a completely randomized design with five treatments and seven replications with eight birds in each. The treatments consisted of a base feed, formulated with corn, soybean meal and corn gluten meal, and supplemented with the synthetic amino acids L-lysine, DL-methionine, L-threonine, L-isoleucine, L-arginine, and L-valine, so as to meet the nutritional requirements for laying hens, except for digestible tryptophan. The basal diet was supplemented with 0.00; 0.017; 0.035; 0.052; and 0.069 g/kg of L-tryptophan in substitution for corn starch with the objective of reaching the levels of 0.151; 0.167; 0.183; 0.199; and 0.215 g/kg of digestible tryptophan in the feed. For the ratio between digestible amino acids and lysine, the recommendation of Brazilian Tables for Poultry and Swine was followed, except for the digestible tryptophan: digestible lysine ratios, which were 19, 21, 23, 25 and 27 for each treatment. The variation in the digestible tryptophan: digestible lysine ratio promoted changes in performance and in the histological characteristics, improving the results. The digestible tryptophan:digestible lysine ratio of 24.5% in the feed of white laying hens in production stage promotes better animal performance and histological results.

-The objective of this study was to evaluate the reduction of protein, the formulation of diets and supplementation of an enzyme complex for laying hens. The layers were distributed in a completely randomized 2 × 2 × 2 factorial arrangement, with two levels of crude protein reduction (0.0 and 4.0 g/kg), two kinds of diet formulation (without and with reformulation, considering 75 kcal of metabolizable energy) and two enzyme supplementations (without and with enzyme complex supplementation), totalizing 8 treatments of 8 layers each, with 7 replications, in a total of 448 laying hens at 30 weeks of age. After data analysis, it was found that the enzyme complex supplementation in the diet of layers improves performance, promotes a similar egg quality and improves the bone and intestinal health of the layers.

-Significant progress in the area of animal production is due to the development of researches on genetics, environment, health, management and nutrition. The search for better management conditions that benefit animal welfare resulted in changes to the installation. The genetic improvement more productive animals has encouraged the number of searches to reduce the incidence of diseases, mainly of metabolic origin. The incorporation in products with higher bioavailability as industrial amino acid and organic minerals, the inclusion of products modifiers enteric of microflora as probiotic, prebiotic, symbiotic, nucleotides and exogenous enzymes, has benefited the use of nutrients are not well absorbed and often unavailable in the diet. Biotechnology latest as nutrition in egg and molecular biology has been used for the benefit of the increase animal productivity.Key Words: amino acids, biotechnology, nutrition, phenomenal progress Progresso científico na produção de monogástricos na primeira década do século XXI RESUMO -Progressos significativos na área da produção animal devem-se ao desenvolvimento de pesquisas nos campos da genética, ambiência, sanidade, manejo e nutrição. A busca por melhores condições de manejo que beneficiassem o bem estar animal provocou modificações nas instalações. O melhoramento genético visando animais mais produtivos tem incentivado o numero de pesquisas para redução da incidência de doenças, principalmente as de origem metabólica. A incorporação na ração de produtos com maior biodisponibilidade como aminoácido industriais e minerais orgânicos, a inclusão de produtos moduladores da microflora entérica como probióticos, prebióticos, simbióticos e nucleotídeos como também, o uso de enzimas exógenas, tem beneficiado a utilização de nutrientes antes pouco absorvidos e muitas vezes indisponíveis na dieta. Biotecnologias mais recentes como a nutrição in ovo e a biologia molecular têm sido utilizadas para benefício da maior produtividade animal.

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The aim of this research was to determine the nutritional requirements of sodium for Japanese quail (Coturnix coturnix Japonica) during the periods of 1 to 21 d and 22 to 40 d of age, as well as to evaluate the residual effect on egg production and densitometry bone traits from 41 to 63 d. Two experiments were developed. Experiment 1: 360 Japanese quail were used, from 1 to 21 d of age. Treatments consisted of 5 sodium levels (0.06, 0.12, 0.18, 0.24, and 0.30%). Experiment 2: 240 Japanese quail were used, from 22 to 40 d. Treatments consisted of 5 sodium levels (0.04, 0.12, 0.20, 0.28, and 0.36%). In both experiments, weight gain, final weight, and feed conversion presented a quadratic trend, whereas water intake presented a linear trend. Treatments did not affect the densitometry of bone traits, although they presented a quadratic influence on tibia ash, calcium, and calcium:phosphorus ratio. Therefore, the nutritional requirement of sodium for Japanese quail from 1 to 21 d and from 22 to 40 d is 0.222% and 0.253%, respectively.