348 research outputs found
Fatores afetando o consumo e utilização de forrageiras de baixa qualidade por ruminantes - revisão.
A quantidade máxima de alimento capaz de ser consumida por um ruminante e de grande importância para o produtor. De um modo geral, quanto maior for o consumo, menor será a quantidade de alimento necessário por unidade de produção. Este fato e que caracteriza a eficiência produtiva de um animal. A conseqüência econômica seria que maiores lucros estariam dependentes da capacidade dos ruminantes em digerir alimentos fibrosos mais baratos e disponíveis em maiores quantidades. O Maximo consumo de uma forragem pelo ruminante depende, primariamente, das taxas de escoamento do rúmen da celulose e hemicelulose. Estas taxas, por sua vez, depende de vários fatores que interferem na atividade da flora microbiana do rúmen, quais sejam: evolução do processo de lignificação com o estágio de maturação das forrageiras, parcial ausência de nutrientes para a microflora como nitrogênio ou minerais e a presença em excesso de agentes bacteriostáticos. Dada a sua importância econômica e cientifica, este assunto vem sendo estudado extensivamente por nutricionistas e fisiologistas em varias partes do mundo, gerando uma enorme gama de conceitos relacionados ao binômio animal-planta, parte dos quais foram reunidos no presente trabalho de revisão.bitstream/item/131377/1/fatores-afetando-o-consumo.pd
Determination of digestible energy values and fermentabilities of dietary fibre supplements: a European interlaboratory study in vivo
The performance of methods to determine energy conversion factors for dietary fibre (DF) supplements and fermentability (D) values of their non-starch polysaccharides (NSP) was investigated. Heats of combustion, digestible energy (DE) and D values were determined on five DF supplements in five European laboratories on five separate occasions. In each instance the DF supplements were fed to juvenile male VVistar rats at two doses, 50 and 100 g/kg basal diet, for 3 weeks with food and faeces collected in the 3rd week. Among-laboratory variations in heats of combustion (DHC<) were <2%. DE values (kJ/g dry weight) at the upper and lower doses respectively were: 10·4 and 9·9 for a high-methoxyl apple pectin, 9·5 and 9·4 for a sugar-beet DF supplement, 12·2 and 12·7 for soyabean DF supplement, 38 and 4·0 for maize bran, and 0·3 and 0·3 for Solka-floc cellulose. Variations among laboratories, among occasions and among animals were <1, <2 and <2·5 kJ/g respectively. The among-occasion: among-laboratory variance ratio for DE was 0·5, suggesting the method performed equally well in all laboratories. There was no evidence of learning or fatigue in the performance of the method. D values were also independent of dose and at the high and lower doses were: pectin 0·92 and 0·95, sugar-beet NSP 0·68 and 0·68, soyabean NSP 0·86 and 0·88, maize bran 0·17 and 0·18, cellulose 0·07 and 0·06. Among-laboratory variance tended to increase with decreasing fermentability and ranged from 0·03 to 0·18. The DE and D data were not significantly different from a previously proposed relationship DE = 0·7 × DHc × D, where DHc is the heat of combustion of the supplement. We conclude that while the among-laboratory variation in the D of difficult-to-ferment NSP is too large for the reliable prediction of energy value the method for the direct determination of DE is both reproducible and repeatable, that DE is independent of dosage of DF supplement up to 100 g/kg diet, and that it is safe to discriminate between energy values with a precision of 3 kJ/g. The conversion of both DE and D to net metabolizable energy for the purpose of food labelling, tables and databases is describe
High-E_T dijet photoproduction at HERA
The cross section for high-E_T dijet production in photoproduction has been
measured with the ZEUS detector at HERA using an integrated luminosity of 81.8
pb-1. The events were required to have a virtuality of the incoming photon,
Q^2, of less than 1 GeV^2 and a photon-proton centre-of-mass energy in the
range 142 < W < 293 GeV. Events were selected if at least two jets satisfied
the transverse-energy requirements of E_T(jet1) > 20 GeV and E_T(jet2) > 15 GeV
and pseudorapidity requirements of -1 < eta(jet1,2) < 3, with at least one of
the jets satisfying -1 < eta(jet) < 2.5. The measurements show sensitivity to
the parton distributions in the photon and proton and effects beyond
next-to-leading order in QCD. Hence these data can be used to constrain further
the parton densities in the proton and photon.Comment: 36 pages, 13 figures, 20 tables, including minor revisions from
referees. Accepted by Phys. Rev.
Inclusive jet cross sections and dijet correlations in photoproduction at HERA
Inclusive jet cross sections in photoproduction for events containing a
meson have been measured with the ZEUS detector at HERA using an integrated
luminosity of . The events were required to have a
virtuality of the incoming photon, , of less than 1 GeV, and a
photon-proton centre-of-mass energy in the range . The measurements are compared with next-to-leading-order (NLO) QCD
calculations. Good agreement is found with the NLO calculations over most of
the measured kinematic region. Requiring a second jet in the event allowed a
more detailed comparison with QCD calculations. The measured dijet cross
sections are also compared to Monte Carlo (MC) models which incorporate
leading-order matrix elements followed by parton showers and hadronisation. The
NLO QCD predictions are in general agreement with the data although differences
have been isolated to regions where contributions from higher orders are
expected to be significant. The MC models give a better description than the
NLO predictions of the shape of the measured cross sections.Comment: 43 pages, 12 figures, charm jets ZEU
Minimization of free radical damage by metal catalysis of multivitamin/multimineral supplements
Multivitamin/multimineral complexes are the most common dietary supplements. Unlike minerals in foods that are incorporated in bioorganic structures, minerals in dietary supplements are typically in an inorganic form. These minerals can catalyze the generation of free radicals, thereby oxidizing antioxidants during digestion. Here we examine the ability of a matrix consisting of an amino acid and non-digestible oligosaccharide (AAOS) to blunt metal-catalyzed oxidations. Monitoring of ascorbate radical generated by copper shows that ascorbate is oxidized more slowly with the AAOS matrix than with copper sulfate. Measurement of the rate of oxidation of ascorbic acid and Trolox® by catalytic metals confirmed the ability of AAOS to slow these oxidations. Similar results were observed with iron-catalyzed formation of hydroxyl radicals. When compared to traditional forms of minerals used in supplements, we conclude that the oxidative loss of antioxidants in solution at physiological pH is much slower when AAOS is present
An overview of the recent developments on fructooligosaccharide production and applications
Over the past years, many researchers have suggested
that deficiencies in the diet can lead to disease states
and that some diseases can be avoided through an adequate
intake of relevant dietary components. Recently, a great interest
in dietary modulation of the human gut has been registered.
Prebiotics, such as fructooligosaccharides (FOS), play a key
role in the improvement of gut microbiota balance and in
individual health. FOS are generally used as components of
functional foods, are generally regarded as safe (generally
recognized as safe status—from the Food and Drug Administration,
USA), and worth about 150€ per kilogram. Due to
their nutrition- and health-relevant properties, such as moderate
sweetness, low carcinogenicity, low calorimetric value,
and low glycemic index, FOS have been increasingly used
by the food industry. Conventionally, FOS are produced
through a two-stage process that requires an enzyme production
and purification step in order to proceed with the chemical
reaction itself. Several studies have been conducted on the
production of FOS, aiming its optimization toward the development
of more efficient production processes and their potential
as food ingredients. The improvement of FOS yield and
productivity can be achieved by the use of different fermentative
methods and different microbial sources of FOS producing
enzymes and the optimization of nutritional and
culture parameter; therefore, this review focuses on the latest
progresses in FOS research such as its production, functional
properties, and market data.Agencia de Inovacao (AdI)-Project BIOLIFE reference PRIME 03/347. Ana Dominguez acknowledges Fundacao para a Ciencia e a Tecnologia, Portugal, for her PhD grant reference SFRH/BD/23083/2005
Measurement of (anti)deuteron and (anti)proton production in DIS at HERA
The first observation of (anti)deuterons in deep inelastic scattering at HERA
has been made with the ZEUS detector at a centre-of-mass energy of 300--318 GeV
using an integrated luminosity of 120 pb-1. The measurement was performed in
the central rapidity region for transverse momentum per unit of mass in the
range 0.3<p_T/M<0.7. The particle rates have been extracted and interpreted in
terms of the coalescence model. The (anti)deuteron production yield is smaller
than the (anti)proton yield by approximately three orders of magnitude,
consistent with the world measurements.Comment: 26 pages, 9 figures, 5 tables, submitted to Nucl. Phys.
- …