Herd A | ||||||||

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

Sows seropositive | 20.0 (1/5) | 80.0 (4/5) | 0.0 (0/5) | 100.0 (5/5) | 0.380 | 10.0 (1/10)^{A} | 90.0 (9/10)^{B} | 0.001 |

Sows IP | 25.6^{AB} | 77.5^{ABC} | 26.8^{B} | 94.4^{C} | 0.005 | 26.2^{A} | 86.0^{B} | 0.000 |

Pigs seropositive | 6.8 (4/59)^{A} | 74.6 (50/67)^{B} | 5.1 (3/59)^{C} | 90.0 (54/60)^{D} | 0.000 | 5.9 (7/118)^{A} | 81.9 (104/127)^{B} | 0.000 |

Pigs IP | 15.6^{A} | 68.1^{B} | 29.0^{A} | 79.6^{B} | 0.000 | 22.3^{A} | 73.2^{B} | 0.000 |

Herd B | ||||||||

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

Sows seropositive | 40.0 (2/5) | 80.0 (4/5) | 0.0 (0/4) | 80.0 (4/5) | 0.532 | 22.0 (2/9)^{A} | 80.0 (8/10)^{B} | 0.023 |

Sows IP | 39.0^{AB} | 56.4^{AB} | 19.9^{A} | 68.8^{B} | 0.049 | 30.5^{A} | 62.6^{B} | 0.017 |

Pigs seropositive | 42.2 (27/64)^{A} | 66.7 (38/57)^{B} | 3.3 (2/60)^{C} | 77.6 (45/58)^{B} | 0.000 | 23.4 (29/124)^{A} | 72.2 (83/115)^{B} | 0.000 |

Pigs IP | 42.4^{A} | 79.3^{B} | 24.6^{C} | 65.2^{D} | 0.000 | 38.5^{A} | 72.5^{B} | 0.000 |

Vaccination status: NV (non-vaccinated sow batches and their pigs) and V (vaccinated sow batches and their pigs). The P value refers to the comparisons between the individual farrowing batches, and the P* value to the comparisons between the summaries of the NV (a–c) and V (b–d) batches. Values with different superscripts within a row are significantly different (P<0.05 and P*<0.05).