A meta-analysis of the between-batch variability in the effect of chilling on the salmonella incidence on pig carcasses
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abstract
The objective of this work was to study the effect of chilling on the occurrence of Salmonella
on pig carcasses at batch level by meta-analysis. Fixed-effects and random-effects metaanalysis
were conducted, and the random-effects solution was preferred to account for the
significant variability in effect size estimated from 51 sampled batches extracted from 13
primary studies. This study results indicated that chilling reduces the Salmonella incidence on
pig carcasses by a mean ratio of ~1.92 (95% CI: 1.36 – 2.70). Multilevel meta-analyses
models investigating study characteristics that could explain the heterogeneity (τ2) in the true
effect size among sampled batches (τ2=0.373), revealed that ‘total sample size’ and ‘carcass
swabbed area’ impact (p<0.05) on the measured effect size of chilling. The fact that swabbed
area explained 62% and total sample size 38% of the total heterogeneity in the chilling true
effect size, gives rise to an awareness that differences in experimental design greatly affects
our substantive conclusion about the effect of chilling on Salmonella recovery. Higher
swabbed areas and greater sample sizes led to more precise and greater estimates of the
decreasing effect of chilling on Salmonella.
