ABSTRACT The present study aimed to estimate digestible protein (DP) requirements for maintenance and growth and assess the efficiency of protein utilization in pacu (Piaractus mesopotamicus) juveniles. A complete randomized design consisted of seven treatments, and five replicates (tanks) per treatment was used. After a one-week acclimation period, 350 pacu juveniles of 27.48 ± 1.8 g (initial average body weight - BW) were equally distributed among 35 tanks (10 fish per tank) of 450 L. Fish were fed with seven graded digestible protein levels (64.5, 111.8, 164.6, 217.1, 264.4, 316.2 and 369.5 g kg−1) three times a day until apparent satiation for 120 days. The monomolecular model parameters including nitrogen maintenance requirement (NMR) (37.76 mg BW0.67 kg−1 d−1), daily nitrogen deposition (ND) (194.8 mg BW0.67 kg−1 d−1), and protein intakes (based on metabolic BW) of 1638, 1902, and 2241 mg kg−1BW0.67 d−1 for 75, 80 and 85% maximum theoretical nitrogen retention (NRmaxT), respectively and the efficiency of protein utilization (529×10−6) were estimated through the relationship between nitrogen intake (NI) and ND. The digestible protein requirements for 75, 80, and 85% of NRmaxT were estimated as 187, 217, and 256 g kg−1 respectively by the monomolecular model based on the daily feed intake of 2% of live BW of pacu juveniles.

Abstract 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% avP; Negative Control 2 (NC2) - reduction of 0.12% avP; 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 cost per OTU does not exceed US$ 1.4 × 10-5, US$1.2 × 10-5 and US$ 1.0 × 10-5 for the concentrations of 120, 180 and 240 OTU, respectively.

A produção industrial de aves e suínos mostrou enormes avanços nos últimos anos, principalmente devido ao aumento dos conhecimentos na área de genética e de nutrição. Na área de avaliação dos alimentos e das exigências nutricionais de animais monogástricos, as melhoras se dão a passos largos, devido á seriedade com que os profissionais encaram a responsabilidade de fazer pesquisa de qualidade dentro e fora do país. Neste trabalho serão abordadas as metodologias que permitem melhorar a utilização dos alimentos de maneira mais eficiente e econômica. Serão citados alguns cuidados e procedimentos essenciais para executar adequadamente experimentos de desempenho com aves e suínos. Na atualidade, para a realização de experimentos com monogástricos, é necessário: definir claramente os objetivos, utilizar animais com peso inicial uniforme, usar número adequado de repetições e de animais por unidade experimental. Testes de médias devem ser usados para as variáveis qualitativas e quando a variável independente for quantitativa aplicar análise de regressão. O nível de significância utilizado (5, 7, 10%) pode variar conforme a importância econômica da característica estudada. A adequada condução dos ensaios, sejam de crescimento ou de digestibilidade, é fundamental para que as ferramentas apresentadas possam ter efetividade, resultando na melhora da produtividade e na redução dos custos e da excreção de nutrientes.

Swine and Poultry production showed enormous progress in the last few years, mainly due to the increased knowledge in genetics and nutrition. In the area of feedstuffs evaluation and nutritional requirements the improvement also was big due to the seriousness of the professionals to make high quality research in Brazil and abroad. This paper shows methodologies that can improve feedstuffs utilization more efficiently with lower costs. Procedures are described for adequate execution of growth experiments with poultry and swine. Actually, to run experiments with monogastric animals it is important to: define clearly the objectives, utilize animals with uniform starting weight, to use adequate number of replicates and animals per experimental unit. Mean test comparation should be used for qualitative variable and regression analysis when the independent variable is quantitative. The level of significance applied may vary (5, 7, 10%) depending upon the economic importance of the parameter evaluated. Adequate execution of growth or digestibility trials is of fundamental importance for the recommendations made in this paper to be effective and result in increased productivity and reduction of costs and nutrient excretion.