Seminário

Multilevel modelling in health: a study of milk production in portuguese dairy farms

Sala 6.4.30, FCUL, Lisboa

Por Pedro Oliveira (Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto).

Paratuberculosis, or Johne's disease, is a chronic granulomatous enteric disease affecting both ruminant and nonruminant animals caused by Mycobacterium avium ssp. paratuberculosis (MAP). No fully effective tools or strategies exist to prevent new infections or disease progression. Diagnosis of MAP infection and measurement of infection effects are difficult because of the long incubation period, lack of diagnostic tests that accurately determine present and future status of the animal, disease dynamics at animal and farm level, and case definition of the positive animal. Multilevel mixed models were used to investigate the association of cow MAP status with variation in milk production and somatic cell count. Corrected milk production, and somatic cell count during 5 lactations lifespan in Portuguese dairy herds, in a total of 191 farms, including 14,829 cows and their respective 36,219 lactations, were considered in the analysis. The data have a longitudinal component which considers the different numbers of observations by cow and a natural hierarchical structure reflecting the "measurement occasion" (first level) nested within cows (second level), and cows nested in farms (third level) Several multivariable multilevel models, having as dependent variable Milk Production or Somatic Cell Count and as explanatory variables Lactation, Cow Status or Farm Status and cross-level interactions were fitted. All models have at least three variance components: a residual variance at level 1, random intercept variances at level 2 and level 3, mimicking the three-level data structure. Models were fitted using Maximum Likelihood Estimation and an unstructured random-effects variance/covariance matrix. The effect of Lactation, with linear and quadratic terms, is significant in all models; these terms account for the curvature associated with Milk Production and Somatic Cell Count along lactations: the production increases from first to third lactation, decreasing afterwards. The variance/covariance analysis confirms the importance of the selected structure. Each level - measurement occasion, Cow and Farm - retains a significant amount of the observed variance in the data. This study provides the first report of MAP effects in Portuguese dairy farms using a Multilevel approach, based on a large size data collection spanning a broad temporal scope, in a three-level structure.

14h30
CEAUL - Centro de Estatística e Aplicações da Universidade de Lisboa

Seminário do Laboratório de Instrumentação e Física Experimental de Partículas, por Pedro Cruz (Northeastern University).

Logótipo do EVM 2024

Por Giosuè Muratore (DM Ciências ULisboa e CMAFcIO).

Logótipo do EVM 2024

Por Pedro Duarte (DM Ciências ULisboa, CMAFcIO).

Título do programa, sobre mosaico de fotografias de jovens cientistas

As candidaturas encontram-se encerradas. Obrigada aos quase 80 candidatos/as!

Fotografia de ilha

Seminários Doutorais no âmbito da disciplina de Projeto de Investigação (Doutoramento em Ciências do Mar).

Logótipo do EVM 2024

Por Maria Manuel Torres (DM Ciências ULisboa e CMAFcIO).

Seminário do Centro de Matemática, Aplicações Fundamentais e Investigação Operacional, por Baptiste Claustre (aluno ENS Lyon, estagiário CMAFcIO).

Logótipo do EVM 2024

Por: Jorge Buescu (DM Ciências ULisboa e CMAFcIO).

Titulo e data do evento, com imagem de ponte sobre o tejo

Um evento organizado no âmbito da Ação COST EURO-MIC, de cujo Comitê de Gestão Elisabete Silva, líder do Bioactive and Multifunctional Materials Lab do BioISI, faz parte.

Logótipo do EVM 2024

Por Jean-Baptiste Casteras (DM Ciências ULisboa e CMAFcIO).

Chegou a hora: os participantes do Programa Ser Cientista vão apresentar os projetos que desenvolveram ao longo de uma semana, acompanhados por docentes e investigadores de CIÊNCIAS. E todos podem assistir!

Imagem do evento

Extended enrolement date until July 12th.

Logótipo do evento, sobre um fundo branco

Um evento de reunião da comunidade nacional nas diversas vertentes da informática, com a ambição de ser o fórum de eleição para a divulgação, discussão e reconhecimento de trabalhos científicos.

Are you ready for this year's edition?

Imagem do evento - título, local e data do evento

Investigação Ecológica ao Serviço da Conservação

A leading venue for presenting and discussing the latest research, industrial practice and innovations in dependable and secure computing.