Table 3.
Results of a random-effects logistic regression (regression model 1 ‘biosecurity model’) of enhanced biosecurity, harvest occasion and sampling period on batch colonization (defined as >123 000 c.f.u./g in pooled caecal samples). Results from a total of 1687 batches sampled between 16 April 2012 and 31 August 2013 included in the UK poultry study on enhanced biosecurity and Campylobacter colonization, UK, 2011–2013
| Factors | OR (95% CI) | P value |
|---|---|---|
| Biosecurity | ||
| Standard (control farms 1) | 1·00 | |
| Enhanced (model farms) | 0·25 (0·14–0·47) | <0·001 |
| Harvest occasion | ||
| Thinning | 1·00 | |
| Depopulation | 1·68 (0·93–3·03) | 0·086 |
| Interaction between biosecurity and harvest occasion | ||
| Model farm and depopulation | 1·85 (0·98–3·50) | 0·059 |
| Effect of depopulation | ||
| In model farm | 3·10 (2·43–3·96) | |
| In control farms 1 | 1·68 (0·93–3·03) | |
| Effect of enhanced biosecurity | ||
| At thinning | 0·25 (0·14–0·47) | |
| At depopulation | 0·47 (0·25–0·89) | |
| Sampling period | ||
| 16 Apr.–31 May 2012 | 3·56 (2·26–5·61) | <0·001 |
| 1 June–31 Aug. 2012 | 5·91 (4·00–8·73) | <0·001 |
| 1 Sept.–30 Nov. 2012 | 1·21 (0·86–1·72) | 0·278 |
| 1 Dec.–28 Feb. 2013 | 1·00 | |
| 1 Mar.–31 May 2013 | 1·09 (0·77–1·54) | 0·619 |
| 1 June–31 Aug. 2013 | 3·04 (2·11–4·38) | <0·001 |
| Constant | 1·60 (0·88–2·88) | 0·121 |
| Standard deviation of random effects | 0·40 (0·25–0·63) | |
| Interclass correlation coefficient (rho) | 0·05 (0·02–0·11) | |
OR, Odds ratio; CI, confidence interval.