ABSTRACT: A reliable determination of endogenous phosphorus (P) excretion is required to measure P utilization in chickens accurately. The objective of this study was to investigate phosphorus (P) retention in broilers fed diets formulated with different feed ingredients. Sixty-four 15-d old broiler chicks were fed diets in which part of the dietary P was provided from dicalcium phosphate, maize, barley or soybean. Level of supplementation of each ingredient was calculated to provide two levels of total P (4.5 or 5.0 g kg−1 feed). Birds received a single injection of 3 MBq of 32P to determine endogenous P excretion using the isotope dilution technique. Four days after injection, blood and excreta were collected for analysis of inorganic and radioactive P. There were no differences among diets in total (p = 0.37) or endogenous (p = 0.65) P excretion or in P retention (p = 0.37) regardless of the supplemental feed material used in each diet. Daily P retention was increased (p = 0.004) as P intake increased, but the proportion of P ingested that was retained was not affected (p = 0.23) by the level of dietary P. The use of an isotopic tracer allows for accurate estimation of endogenous P in excreta, ranging from 0.24 to 0.42 mg P g−1 dry matter intake. The retention of P in growing chickens was not changed when 10-20 % of total P was provided by maize, barley or soybean.

ABSTRACT. Because of the relatively long growing cycle and the high cost of research into turkey production and nutrition, the potential benefits from modelling growth in this avian species are considerable. Though there are many studies aimed at evaluating animal growth models, the number of studies targeting growth models in turkeys is quite limited. In this paper we present a sinusoidal function to describe the evolution of growth in turkeys as a function of time based on data published by Aviagen. The new function was evaluated with regard to its ability to describe the relationship between body weight and age in turkeys and was compared to four standard growth functions: the Gompertz, logistic, Lopez, and Richards. The results of this study show that the new sinusoidal function precisely describes the growth dynamics of turkeys. Fitting the functions to different data profiles nearly always led to the same or less maximized log-likelihood values for the sinusoidal equation, indicating its suitability in describing growth data from turkeys.

O objetivo neste estudo foi investigar a influência da freqüência de corte, da estação de colheita e da adubação nitrogenada no rendimento e na composição botânica da forragem recolhida de um prado de montanha. O prado foi dividido em 22 parcelas, cada uma com nível de fertilização N P K. O estudo durou sete anos e, durante os três primeiros (1985-1987), cada parcela foi cortada duas vezes por ano (junho e setembro), seguindo um sistema de aproveitamento tradicional, ao passo que, nos anos 1989-1991, cada parcela foi cortada três vezes por ano (primavera, verão e outono), seguindo um sistema de aproveitamento mais intensivo. O fertilizante nitrogenado favoreceu o desenvolvimento das gramíneas na primavera, reduzindo a proporção de leguminosas no sistema de dois cortes anuais, de modo que as gramíneas alcançaram etapa avançada de maturidade antes do primeiro corte, ao final do mês de junho. No entanto, com o sistema de três cortes anuais, o primeiro corte foi realizado mais cedo, na primavera. Conseqüentemente, a produção da biomassa de leguminosas aumentou significativamente, tanto no primeiro corte como nos rebrotes subseqüentes. Nenhum efeito significativo na produção total de forragem em resposta à fertilização nitrogenada foi observado no sistema de aproveitamento mais intensivo. Portanto, o sistema de três cortes, sem fertilização nitrogenada, parece ser a prática mais conveniente para o manejo desses prados de montanha, botanicamente complexos. Os resultados obtidos neste estudo podem contribuir para projetos de fertilização e práticas de manejo de prados de montanha, utilizados para produção de feno, para otimizar sua produtividade e sustentabilidade.

The aim of the present study was to investigate the influence of cutting frequency, harvest season and nitrogen fertilization on yield and floristic composition of the herbage harvested from a mountain meadow. The meadow was divided into 22 plots, each receiving a different N P K fertilization treatment. The study lasted seven years, and during the first three years (1985-1987) each plot was harvested twice per year (June and September) according to a traditional harvest system, whereas in the years 1989-1991 each plot was harvested three times per year (spring, summer and autumn) following a more intensive harvest system. Nitrogen fertilizer favoured the development of the grasses in spring, thus reducing the proportion of legumes in the two cut harvest system, whereas grasses reached an advanced stage of maturity before the first cut in late June. However, the three cut harvest system entailed an earlier first cut in spring. As a result, the production of legume biomass was significantly increased both in the first cut and in the subsequent regrowths. No significant response in total herbage production to the N fertilizer was observed in the more intensive harvest system. Therefore, the three cut harvest system without nitrogen fertilization seemed to be the most suitable practice for the management of these botanically-complex mountain meadows. These results may contribute to design fertilization and management practices of mountain hay meadows to optimize their productivity and sustainability.