Issue |
Vet. Res.
Volume 34, Number 5, September-October 2003
Mastitis of dairy ruminants
|
|
---|---|---|
Page(s) | 493 - 505 | |
DOI | https://doi.org/10.1051/vetres:2003029 | |
How to cite this article | Vet. Res. (2003) 493-505 |
DOI: 10.1051/vetres:2003029
Statistical modelling for clinical mastitis in the dairy cow: problems and solutions
Patrick Gasqui and Jacques BarnouinUnité d'Épidémiologie Animale, INRA, 63122 Saint-Genès-Champanelle, France
(Received 9 October 2002, accepted 16 June 2003)
Abstract
Modelling case occurrence and risk factors for clinical mastitis, as a key multifactorial disease in the dairy cow, requires
statistical models. The type of model used depends on the choice of perception or the study level: herd, lactation, animal,
udder and quarter. The validity of the tests that are performed through these models is especially ensured when hypotheses
of independence between statistical units are respected, and when the model adjustments do not involve overdispersion faced
with the observed data. In the article, the main sources of overdispersion are identified according to the different levels
of perception of mastitis risk. Then, the proposed solutions to control for overdispersion at each study level are discussed
and the difficulty to compare the study results is highlighted through a variety of methodological choices of the authors.
Two main categories of models are used for modelling clinical mastitis, i.e. generalist exploratory models and explanatory
designed models. The contribution of the explanatory models to improve modelling accuracy and relevance is documented through
the two main published methodological approaches, the first one being based on a states model, and the second on a survival
model. The integration and optimisation of such explanatory modelling methods should be possible in the future in order to
develop a more global explanatory model including herd risk factors, which could pertinently predict udder infections (both
clinical and subclinical) at the cow, lactation, or even udder and
quarter levels.
Key words: clinical mastitis / dairy cow / epidemiology / modelling / overdispersion
Correspondence and reprints: Patrick Gasqui Patrick.Gasqui@clermont.inra.fr
© INRA, EDP Sciences 2003