2.5. Statistical analysis
Data from the U.S. and the European studies were analysed separately. Statistical analysis of the data was performed with a computer program (SPSS release 7.5, SPSS Inc., Chicago, IL, USA). For PAG concentrations in plasma and for PMN functions, analysis of variance was performed using a mixed model with time (week relative to parturition) and parity as fixed factors and cows within parity as a random factor:
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