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101.
M. Schulin-Zeuthen E. Kebreab J. Dijkstra S. Lopez A. Bannink H. Darmani Kuhi J.H.M. Thornley J. France 《Animal Feed Science and Technology》2008,143(1-4):314
This study was undertaken to introduce the Schumacher equation and compare it with established functions for describing growth in pigs. The relationship between live weight (LW) and cumulative feed intake was also investigated. A database was constructed from three independent trials in which LW, age and intake were measured from birth to 937 days. Three growth functions were used for analysis of growth versus age: Gompertz, Schumacher and Weibull; and the Richards and monomolecular equations were used for analysis of cumulative feed intake versus LW. The growth functions have different points of inflexion. Liveweight at inflexion is Wf/e for the Gompertz, where Wf is the final weight, Wf/e2 for the Schumacher, and Wf − (Wf − W0) exp[−(n − 1)/n] for the Weibull, where W0 is initial body weight and n is a shape parameter. Meta-analysis of the data using mixed model and nonlinear regression procedures was conducted to identify the most appropriate growth function. Functions were compared using F-tests or Bayesian Information Criteria, which give a value based on best fit and number of parameters in the model. The three equations were fitted to five individual pig growth profiles and to the composite data. Although the Weibull had a lower residual mean square, it did not significantly improve the fit compared to the simpler models and appears to be over-parameterised. The results suggest that model selection should be based on the type and amount of data available for analysis. Residuals plot showed that Schumacher and Weibull better predict the initial growth phase, however, all models showed largest magnitude of residuals towards the end of the growth profile. The monomolecular equation was most appropriate for describing LW against cumulative feed intake and may be used to formulate diets based on the efficiency of conversion of feed to LW at various stages of the animal's life span. 相似文献
102.
A simulation model “CTR Dairy” to predict the supply of nutrients in dairy cows managed under discontinuous feeding patterns 总被引:1,自引:0,他引:1
P. Chilibroste J. Dijkstra P.H. Robinson S. Tamminga 《Animal Feed Science and Technology》2008,143(1-4):148
A simulation rumen model has been developed to function under non-steady state conditions in order to allow prediction of nutrient availability in dairy cows managed under discontinuous feeding systems. The model simulates availability of glycogenic, aminogenic and lipogenic nutrients to lactating dairy cows fed discontinuously. The model structure considers input of up to three different feeds fed independently at any time during the day. Feeds are described by their nitrogen (N), carbohydrate and fatty acid fractions. The N containing feed fractions include ruminally undegraded crude protein (CP), ruminally insoluble but potentially degradable CP, ruminally soluble CP and ammonia N. The feed carbohydrate fractions include ruminally undegradable neutral detergent fibre (NDF), ruminally degradable NDF, ruminally insoluble starch, ruminally soluble starch and sugars. The fatty acids in the feeds are divided between long chain fatty acids and volatile fatty acids (VFA). Additionally four pools were defined representing absorption of amino acids, glucose, long chain fatty acids and volatile fatty acids. The rumen microbial population is represented as a single pool. Besides a flexible structure, new features to the extant model include adoption of the concept of chewing efficiency (or chewing effectiveness) during eating, variable fractional ruminal absorption rates of VFA and variable fractional ruminal degradation rates of NDF as a function of rumen liquid pH, as well as a variable rumen volume which directly affects rumen concentrations of metabolites. The model continuously (i.e., by minute) predicts release of soluble components from the feeds in the rumen, concentration and absorption of fermentation end products in the rumen, rumen pools of nutrients and microbial biomass dynamics, as well as passage of microbial biomass and non-fermented nutrients from the rumen, in response to various feeding strategies. Model evaluation covered a wide range of feeding strategies that included pasture and housed feeding systems. Overall, the mean square prediction error (MSPE) as a percentage of the observed mean was relatively low (<10%) with a high amount of the total variation explained by random variation (>65%). Deviation from unity varied between 23% (rumen dry matter content) and 25% (NDF), indicating some consistent over and/or under prediction. A more detailed evaluation was done based on studies available that reported diurnal behaviour of key model outputs such as rumen pools, rumen pH, and rumen VFA. The predictions broadly simulated the observed values quantitatively, relative to general diurnal patterns, and relative to differences between treatments in the predicted diurnal patterns. Results show that the model provides a tool to assess potential outcomes of changing feeding strategies which may be particularly valuable in assessing selection of feeds, amounts and times of the day to offer the feeds. The continuous nature of the simulated output also allows determination of the time(s) of the day that ruminal (and/or post-ruminal) delivery of nutrients may limit ruminal output of nutrients (and/or availability of nutrients) to support milk nutrient synthesis. 相似文献
103.
Vincent J. Kalkman Viola Clausnitzer Klaas-Douwe B. Dijkstra Albert G. Orr Dennis R. Paulson Jan van Tol 《Hydrobiologia》2008,595(1):351-363
Larvae of almost all of the 5,680 species of the insect order Odonata (dragonflies and damselflies) are dependent on freshwater
habitats. Both larvae and adults are predators. The order is relatively well studied, and the actual number of species may
be close to 7,000. Many species have small distributional ranges, and are habitat specialists, including inhabitants of alpine
mountain bogs, seepage areas in tropical rain forests, and waterfalls. They are often successfully used as indicators for
environmental health and conservation management. The highest diversity is found in flowing waters in rain forests of the
tropics, the Oriental and Neotropical regions being the most speciose. This paper discusses diversity, summarises the biogeography
of dragonflies in the different biogeographical regions and gives the total number of species and genera per family per biogeographical
region. Examples are given of areas of particular diversity, in terms of areas of endemism, presence of ancient lineages or
remarkable recent radiations but no well-based review of areas with high endemism of dragonflies is available so far. The
conservation status of dragonflies is briefly discussed. Species confined to small remnants of forest in the tropics are most
under threat of extinction by human activities.
Guest editors: E. V. Balian, C. Lévêque, H. Segers and K. Martens
Freshwater Animal Diversity Assessment 相似文献
104.
Datasets from the mitochondrial gene regions NADH dehydrogenase subunit I (ND1) and cytochrome c oxidase subunit I (COI) of the 20 species in the New Zealand wolf spider (Lycosidae) genus Anoteropsis were generated. Sequence data were phylogenetically analysed using parsimony and maximum likelihood analyses. The phylogenies generated from the ND1 and COI sequence data and a previously generated morphological dataset were significantly congruent (p<0.001). Sequence data were combined with morphological data and phylogenetically analysed using parsimony. The ND1 region sequenced included part of tRNALeu(CUN), which appears to have an unstable amino-acyl arm and no TψC arm in lycosids. Analyses supported the existence of five species groups within Anoteropsis and the monophyly of species represented by multiple samples. A radiation of Anoteropsis species within the last five million years is inferred from the ND1 and COI likelihood phylograms, habitat and geological data, which also indicates that Anoteropsis arrived in New Zealand some time after it separated from Gondwana. 相似文献
105.
The effects of CO2 elevation on the dynamics of fine root (FR) mass and ectomycorrhizal (EM) mass and colonization were studied in situ in a Florida scrub oak system over four years of postfire regeneration. Soil cores were taken at five dates and sorted to assess the standing crop of ectomycorrhizal and fine roots. We used ingrowth bags to estimate the effects of elevated CO2 on production of EM roots and fine roots. Elevated CO2 tended to increase EM colonization frequency but did not affect EM mass nor FR mass in soil cores (standing mass). However, elevated CO2 strongly increased EM mass and FR mass in ingrowth bags (production), but it did not affect the EM colonization frequency therein. An increase in belowground production with unchanged biomass indicates that elevated CO2 may stimulate root turnover. The CO2-stimulated increase of belowground production was initially larger than that of aboveground production. The oaks may allocate a larger portion of resources to root/mycorrhizal production in this system in elevated rather than ambient CO2. 相似文献
106.
107.
108.
Federico Fogolari Haritha Haridas Alessandra Corazza Paolo Viglino Davide Corà Michele Caselle Gennaro Esposito Luigi E Xodo 《BMC structural biology》2009,9(1):64-20
Background
Independent surveys of human gene promoter regions have demonstrated an overrepresentation of G3X n1G3X n2G3X n3G3 motifs which are known to be capable of forming intrastrand quadruple helix structures. In spite of the widely recognized importance of G-quadruplex structures in gene regulation and growing interest around this unusual DNA structure, there are at present only few such structures available in the Nucleic Acid Database. In the present work we generate by molecular modeling feasible G-quadruplex structures which may be useful for interpretation of experimental data. 相似文献109.
Daniela Camargos Costa Ana Paula Madureira Lara Cotta Amaral Bruno Ant?nio Marinho Sanchez Luciano Teixeira Gomes Cor Jésus Fernandes Fontes Jean Ezequiel Limongi Cristiana Ferreira Alves de Brito Luzia Helena Carvalho 《Memórias do Instituto Oswaldo Cruz》2014,109(1):21-28
The polymerase chain reaction (PCR)-based methods for the diagnosis of malaria
infection are expected to accurately identify submicroscopic parasite carriers.
Although a significant number of PCR protocols have been described, few studies have
addressed the performance of PCR amplification in cases of field samples with
submicroscopic malaria infection. Here, the reproducibility of two well-established
PCR protocols (nested-PCR and real-time PCR for the Plasmodium 18
small subunit rRNA gene) were evaluated in a panel of 34 blood field samples from
individuals that are potential reservoirs of malaria infection, but were negative for
malaria by optical microscopy. Regardless of the PCR protocol, a large variation
between the PCR replicates was observed, leading to alternating positive and negative
results in 38% (13 out of 34) of the samples. These findings were quite different
from those obtained from the microscopy-positive patients or the unexposed
individuals; the diagnosis of these individuals could be confirmed based on the high
reproducibility and specificity of the PCR-based protocols. The limitation of PCR
amplification was restricted to the field samples with very low levels of
parasitaemia because titrations of the DNA templates were able to detect < 3
parasites/µL in the blood. In conclusion, conventional PCR protocols require careful
interpretation in cases of submicroscopic malaria infection, as inconsistent and
false-negative results can occur. 相似文献