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Meta-analyses of experimental data in animal nutrition⋆

Published online by Cambridge University Press:  01 August 2008

D. Sauvant ,
P. Schmidely ,
J. J. Daudin  and
N. R. St-Pierre
D. Sauvant*
Affiliation:
UMR Physiologie de la Nutrition et Alimentation, INRA-AgroParisTech, 16 rue Claude Bernard, 75231 Paris Cedex 05, France
P. Schmidely
Affiliation:
UMR Physiologie de la Nutrition et Alimentation, INRA-AgroParisTech, 16 rue Claude Bernard, 75231 Paris Cedex 05, France
J. J. Daudin
Affiliation:
ENGREF, Mathématique et Informatique Appliquée, INRA-AgroParisTech, 16 rue Claude Bernard, 75231 Paris Cedex 05, France
N. R. St-Pierre
Affiliation:
Department of Animal Sciences, The Ohio State University, 2029 Fyffe Rd., Columbus, OH-43210, USA
*
E-mail: sauvant@agroparistech.fr
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Abstract

Research in animal sciences, especially nutrition, increasingly requires processing and modeling of databases. In certain areas of research, the number of publications and results per publications is increasing, thus periodically requiring quantitative summarizations of literature data. In such instances, statistical methods dealing with the analysis of summary (literature) data, known as meta-analyses, must be used. The implementation of a meta-analysis is done in several phases. The first phase concerns the definition of the study objectives and the identification of the criteria to be used in the selection of prior publications to be used in the construction of the database. Publications must be scrupulously evaluated before being entered into the database. During this phase, it is important to carefully encode each record with pertinent descriptive attributes (experiments, treatments, etc.) to serve as important reference points for the rest of the analysis. Databases from literature data are inherently unbalanced statistically, leading to considerable analytical and interpretation difficulties; missing data are frequent, and data structures are not the outcomes of a classical experimental system. An initial graphical examination of the data is recommended to enhance a global view as well as to identify specific relationships to be investigated. This phase is followed by a study of the meta-system made up of the database to be interpreted. These steps condition the definition of the applied statistical model. Variance decomposition must account for inter- and intrastudy sources; dependent and independent variables must be identified either as discrete (qualitative) or continuous (quantitative). Effects must be defined as either fixed or random. Often, observations must be weighed to account for differences in the precision of the reported means. Once model parameters are estimated, extensive analyses of residual variations must be performed. The roles of the different treatments and studies in the results obtained must be identified. Often, this requires returning to an earlier step in the process. Thus, meta-analyses have inherent heuristic qualities.

Keywords

meta-analysismixed modelsnutrition
Type
Full Paper
Information
animal , Volume 2 , Issue 8 , August 2008 , pp. 1203 - 1214
Copyright
Copyright © The Animal Consortium 2008

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Footnotes

⋆

*Salaries and research support were provided by state and federal funds appropriated to the Ohio Agricultural Research and Development Center, the Ohio State University.

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