Herd A
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a | b | c | d | P value | a–c (NV) | b–d (V) | P* value | |

12–24 hours post-farrowing
| 0.0 (0/5) | 0.0 (0/5) | 20.0 (1/5) | 0.0 (0/5) | 0.999 | 10.0 (1/10) | 0.0 (0/10) | 0.999 |

Herd B
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a | b | c | d | P value | a–c (NV) | b–d (V) | P* value | |

12–24 hours post-farrowing
| 0.0 (0/5) | 40.0 (2/5) | 40.0 (2/5) | 20.0 (1/5) | 0.902 | 20.0 (2/10) | 30.0 (3/10) | 0.608 |

Vaccination status: NV (non-vaccinated sow batches) and V (vaccinated sow batches). The P value refers to the comparisons between the individual sow batches, and the P* value to the comparisons between the summaries of the NV (a–c) and V (b–d) batches. Differences between batches were not statistically significant (P>0.05).