Paulo Justiniano Ribeiro Junior

Contagem de células somáticas e produção de leite em vacas holandesas confinadas

ABSTRACT - The relationship between milk somatic cells count (SCC) and milk yield has been the aim of countless researchesin several countries; however, in Brazil, the literature related to this subject is scarce. Therefore, the objective of this st udy is to verifyif the losses in milk yield due to SCC increase are proportional to the yield, or absolute (independent of it) and starting fro m which SCC,the losses become evident. For this study, 13.725 observations were used, collected monthly from 6 different herds, from Januar y/2001up to June/2002. The analysis model, for lactation curve, was based upon the incomplete gama function, considering the effects of lactationorder, herd and calving season. The SCC entered in that model in two ways: as multiplicative factor (representing relative loss es) andas addictive factor (representing absolute losses). The best model was chosen based on the information criteria of Schwarz (BIC ). It isconcluded that the losses are absolute, becoming evident from 17.000 cells/mL, and they are 238 and 868 mL/day for each increas e ofone unit in the natural logarithm scale, starting from that SCC, respectively, for primiparous and multiparous.Key Words: SCC, subclinical mastitis, bovine mastitis, milk yield

Aplicação de métodos geoestatísticos para identificação de dependência espacial na análise de dados de um ensaio de espaçamento florestal em delineamento sistemático tipo leque

Os delineamentos sistematicos se destacam pela sua compacidade e abrangencia e por permitir testar maior numero de espacamentos possiveis. No entanto, nao e utilizado devido ao arranjo sistematico (nao casualizado) das plantas e a alta sensibilidade para valores perdidos. O objetivo deste trabalho foi descrever o modelo geoestatistico e metodos associados de inferencia no contexto de analise de experimentos nao aleatorizados, reportando resultados aplicados para identificar a dependencia espacial em um particular experimento em delineamento sistematico tipo leque de Eucalyptus dunnii. Tambem foram propostas, analisadas e comparadas diferentes alternativas para tratar dados faltantes que pudessem advir de falhas e, ou, mortalidade de plantas. Os dados foram analisados seguindo-se tres modelos que diferiram, com co-variaveis, na forma de tratar os dados faltantes. Para cada um destes foi construido um semivariograma, com o ajuste de tres modelos de funcao de correlacao, sendo os parâmetros estimados pelo metodo de maxima verossimilhanca e selecionados pelo criterio de Akaike. Esses modelos, com e sem o componente espacial, foram comparados pelo teste da razao de verossimilhanca. De acordo com os resultados, verificou-se que: (1) as co-variaveis interagiram positivamente com a variavel de resposta, evitando que dados coletados sejam desperdicados; (2) a comparacao dos modelos, com e sem o componente espacial, nao confirmou a existencia de dependencia; (3) a incorporacao da estrutura de dependencia espacial aos modelos observacionais recuperou a capacidade de fazer inferencias validas na ausencia de aleatorizacao, permitindo contornar problemas operacionais e, assim, garantindo que os dados possam ser submetidos a uma analise classica.

Autologistic model with an application to the citrus "sudden death" disease

The citrus sudden death (CSD) disease affects dramatically citrus trees causing a progressive plant decline and death. The disease has been identified in the late 90s in the main citrus production area of Brazil and since then there are efforts to understand the etiology as well as the mechanisms its spreading. One relevant aspect of such studies is to investigate spatial patterns of the occurrence within a field. Methods for determining whether the spatial pattern is aggregated or not has been frequently used. However it is possible to further explore and describe the data by means of adopting an explicit model to discriminate and quantify effects by attaching parameters to covariates which represent aspects of interest to be investigated. One alternative involves autologistic models, which extend a usual logistic model in order to accommodate spatial effects. In order to implement such model it is necessary to take into account the reuse of data to built spatial covariates, which requires extensions in methodology and algorithms to assess the variance of the estimates. This work presents an application of the autologistic model to data collected at 11 time points from citrus fields affected by CSD. It is shown how the autologistic model is suitable to investigate diseases of this type, as well as a description of the model and the computational aspects necessary for model fitting.

Influence of incorporating geometric anisotropy on the construction of thematic maps of simulated data and chemical attributes of soil

The study on spatial variability of soil properties performed through geostatistical techniques allow us to identify the spatial distribution of phenomena by means of a spatial model that considers degree of dependence among observed data, depending on distance and also the direction that separate them, if there is geometric anisotropy, in other words, a directional trend in spatial continuity. However, the main difficulty in decision making regarding the use of anisotropic spatial model focuses on its relevance to the parameters that express the geometric anisotropy in a spatial model exercise in relation to the estimation space. This study aims at identifying the degree of influence of geometric anisotropy on the accuracy of spatial estimation using simulated data sets with different sample sizes and soil chemical properties such as: Fe, potential acidity (H + Al), organic matter and Mn. Comparing the isotropic and anisotropic models, especially for smaller sample sizes (100 and 169) showed an increased sum of squares of differences between predictions anisotropy factor (Fa) equals 2. Furthermore, from Fa equals 2.5, over 50% of the simulations showed values of overall accuracy (OA) of less than 0.80 and values for the concordance index Kappa (K) and Tau (T) from 0.67 to 0.80, indicating differences between thematic maps. Similar conclusions were obtained for chemical properties of the soil, from Fa equals 2, showing that there are relevant differences regarding the inclusion or not of geometric anisotropy.

Influence of boron, nitrogen sources and soil pH on the control of club root of crucifers caused by Plasmodiophora brassicae

Effects of Boron (B) doses and nitrogen sources (N) at different levels of soil pH on the control of clubrootwas investigated in transplants of chinese cabbage grown in pots containing field soil.. B dissolved in water was applied at 0, 5, 10, 20 and 30 mg.kg-1 of soil of pH 5.5, 6.2 and 7.3 on the day before transplanting. N sources tested (ammonium sulfate, urea and calcium nitrate) were applied to soil of pH 5.5 and 7.3. Seedlings were inoculated with a suspension of resting spores of the pathogen at transplanting and assessed for clubroot severity after 45 days. The disease was severe (70%) when the B dose was less than 10 mg.kg-1 and the pH less than 6.0, but milder (26%) when the B dose was 10 to 30 mg.kg-1 soil at pH values higher than 6.5. Clubroot was least severe when calcium nitrate was used in soil of pH 6.5. Clubroot severity correlated negatively with concentrations of N, Ca, Mg and B in the foliage. We conclude that use of 10 to 30 mg.kg-1 boron and calcium nitrate in soil of pH 6,5 or 7,3 was effective in reducing club root severity.

Verossimilhança na seleção de modelos para predição espacial

Statistical modeling of spatial attributes aims to estimate dependence parameters, used to interpolate values at unsampled locations within the study area. Thus, the modeling process is conducted with some statistical criteria that ensure reliable predictions representing the actual local variability. This study evaluates different formulations of the Gaussian geostatistical model to reconstruct the surface of phosphorus over the area from the available measurements on 48 experimental plots located in Xanxere/SC with emphasis on the methodological framework. Choices of covariates in the model and for data transformation define four modeling options to be assessed. The Matern correlation function was used, evaluated at values 0.5; 1.5 and 2.5 for smoothness parameter. Models were compared by the maximized logarithm of the likelihood function and also by cross validation. The model with transformed response variable, including coordinates of the area as covariates and the value of 0.5 for the smoothness parameter was selected. The cross validation measures did not add relevant information to the likelihood, and the analysis highlights care must be taken with globally or locally atypical data, as well as the need of objective choice based on different candidate models which ought to be the focus of geostatistical modeling to ensure results compatible with reality.

Modelo autologístico espaço-temporal com aplicação à análise de padrões espaciais da leprose-dos-citros

The goal of this study was to propose modeling strategies applied to the analysis of citrus leprosis incidence, through the use of a spatial temporal autologistic model. We evaluated the adequacy of autologistic model to consider data collected at different times; to detect spatial-temporal patterns through different neighboring structures; to consider the effect of covariates from previous times; and assessing the effect of the presence of the disease vector in the probability of new infections occurrence. The spatial temporal autologistic model adopted has extended the usual logistic model, in which the neighboring structures is described by means of covariates built from the status of plants nearby, at the same or at previous times. Data regarding the presence of the leprosis on plants were collected at field points referenced in space, over a period of approximately two years. Models detect the presence of spatial patterns on new infections for the studied neighboring structures, at the same or previous time. Additionally, probability estimates of a plant become infected can be obtained from the fitted models, given the occurrence of the disease and vector.

Contagem de células somáticas e produção de leite em vacas holandesas de alta produção

The goal of this paper was to evaluate if losses in milk yield due to increase in somatic cells count are proportional or independent of the level of production. A total of 7,756 observations, monthly collected from a single herd from September/2000 up to June/2002, were used. The lactation curve was modeled by the incomplete gamma function, considering the effects of lactation order, calving season, peripartum disorder incidence and body condition score at calving. Somatic cells count was added to the model as a multiplicative factor, representing relative losses, and as an additive factor, representing absolute losses. The best model was chosen based on the information criteria of Schwarz (BIC). The losses are absolute, becoming evident from 14,270 cells/mL, and they are 184 and 869 g/day for each increase of one unit in the natural logarithm scale, starting from that somatic cells count, for primiparous and multiparous cows, respectively.

Comparação das comunidades de Entomobryidae e Isotomidae (Collembola) entre plantio direto em três níveis de fertilidade, plantio convencional e um ecossistema natural (campo nativo) em Ponta Grossa, Paraná, Brasil

This work had as objective to compare the communities of Sminthuroidea and Onychiuridae (Collembola) among no-tillage in three fertility levels, conventional tillage and a natural ecosystem (native grassland). In the conventional tillage and in the no-tillage in area of medium fertility, the community of Sminthuroidea had regular fluctuation along the period of the experiment, but wtth low densities. The no-tillage in area of high fertility presented a populational pick in the autumn; the no-tillage in area of low fertility, in the spring; and, the natural ecosystem, in the summer. As the final mean density of the population of Sminthuroidea, was observed that the no-tillage in area of low fertility went numerically superior to the others, proceeded by the natural ecosystem, no-tillage in area of high fertility, conventional tillage, and, finally, no-tillage in area of medium fertility. Onychiuridae had three populational picks in the no-tillage in area of low fertility: being a larger in the winter and other two, smaller in the summer and in the autumn. In the no-tillage in area of medium fertility presented only a populational pick in the winter. In the other treatments there was not significantly populational picks. In relation to the final mean density ofthe community of Onychiuridae, the no-tillage plantation in area of low fertility was superior, proceeded by the other treatments of no-tillage, and, in third plan, the natural ecosystem and the conventional tillage.

Survival analysis: a tool in the study of post-harvest diseases in peaches

A analise de sobrevivencia e aplicada quando o tempo ate a ocorrencia de um evento for o objeto de interesse. Em doencas de plantas, dados dessa natureza sao rotineiramente coletados, embora aplicacoes do metodo sejam pouco comuns. O objetivo deste trabalho foi utilizar dois estudos de doencas em pos-colheita de pessegos, considerando-se safras conjuntamente e a existencia de efeito aleatorio, compartilhado por frutos de uma mesma arvore, para descrever as principais tecnicas em analise de sobrevivencia. Aplicaram-se a tecnica nao parametrica de Kaplan-Meier e a estatistica log-rank, alem do modelo semiparametrico de riscos proporcionais, de Cox, para estimar o efeito de cultivares e do numero de dias apos a floracao plena sobre a sobrevivencia ao sintoma de podridao parda e sobre o risco instantâneo de expressa-lo, em duas safras consecutivas. A analise conjunta com efeito basal, variando entre safras, e a verificacao do efeito de arvore como fator de agrupamento com efeito aleatorio, mostraram-se adequadas para interpretar o fenomeno avaliado (doenca) e podem ser ferramentas importantes para substituir ou complementar as analises convencionais, respeitando-se as naturezas da variavel e do fenomeno.