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
Fotografia de fábrica a emitir poluição para a atmosfera

The course aims at enabling the participants to use different methods to measure the impacts of pollutants on ecosystems.

Um concurso de programação dirigido aos alunos do ensino secundário (11.º e 12.º anos), que visa promover a prática e o gosto pela programação.

Banner Dia Aberto de CIÊNCIAS 2025.

Bem-vindos a Ciências ULisboa!

Fotografia de Chapim-azul

The goal of this course is to provide the participants with the most recent and practical knowledge on the use of Functional Diversity.

Título/data/local do evento, logótipos das entidades organizadoras e fotografia de peixe

The event aims to facilitate the exchange of information and knowledge among professionals to advance the understanding, collaboration and capabilities of aquaculture to respond to the impact of climate change in a rapidly changing global environment.

Uma oportunidade única para interagir com a comunidade global de computação científica, com inscrições (preço reduzido) até 02 de maio.

Logótipo Moodle

Ação de formação para docentes e investigadores de CIÊNCIAS.

Químico a escrever fórmulas num quadro

Curso acreditado para efeitos de progressão na carreira dos professores do Ensino Básico e Secundário do Grupo 510 (CCPFC/ACC-118288/22), com candidaturas até 18 de maio.

Título/data/local do evento e fotografia do mar

Quais são os conceitos-chave para enfrentar os atuais desafios marinhos e costeiros? 

Título da conferência, sobre um quadro de ardósia

The conference focuses on "Algebra and its role in Computer Science", with special emphasis on the areas of study related to the work of M. V. Volkov, such as semigroups and automata.

Computability in Europe (CiE) is an interdisciplinary series of international conferences organised by the Association Computability in Europe (ACiE).

Logótipo do evento, sobre fotografia dos Açores

An international symposium that convenes researchers specializing in various disciplines focused on the terrestrial and marine flora and vegetation of the Macaronesian region (Azores, Madeira, Selvagens, Canary Islands, and Cabo Verde).

Composição de imagens relativas à área das ciências forenses

O curso visa dotar os formandos, com formação universitária nas mais diversas áreas do saber, com os conhecimento necessários à integração de equipas profissionais multidisciplinares nas áreas Médico-Legais e Forenses, em Laboratórios ou Serviços Médico-Legais e Forenses.

Cientista a trabalhar com tubos de ensaio

Este curso forma profissionais para atividade na área das Análises Clínicas ou Patologia Clínica. Irão adquirir os conhecimentos essenciais à integração de equipas profissionais multidisciplinares na área das Análises Clínicas/Patologia Clínica, em laboratórios privados, públicos, hospitalares ou do Estado.

Páginas