Table 1 Herd characteristics and PCR prevalence and seroprevalence of the ten farrow-to-finish farms included in the study
| Â | Farm 1 | Farm 2 | Farm 3 | Farm 4 | Farm 5 | Farm 6 | Farm 7 | Farm 8 | Farm 9 | Farm 10 |
|---|---|---|---|---|---|---|---|---|---|---|
Number of sows | 450 | 960 | 430 | 270 | 370 | 2400 | 1600 | 400 | 280 | 1000 |
Breed | Topigs20 | Danbred | Danbred | Danbred | Topigs20Â - TN70 | Topigs20 | Danbred | Danbred | Hypor | TN70 |
Batch farrowing system for the sows (…week system) | 4 | 4 | 4 | 4 | 3 | 1 | 1 | 4 | 3 | 1 |
Average parity number | 3.2 | 4.0 | 3.7 | 4.9 | 3.0 | 3.7 | 3.6 | 4.0 | 3.8 | 3.0 |
Purchase of gilts | + | − | + | + | + | + | + | − | − | + |
Quarantine for purchased gilts | + | N.A | + | + | + | + | + | N.A | N.A | + |
Gilts purchased from Mhyo negative farm | − | N.A | + | + | − | − | − | N.A | N.A | − |
Duration of quarantine (weeks) | 4 | N.A | 7 | 4 | 6 | 3 | 6 | N.A | N.A | 5 |
Quarantine unit located in separate stable | + | N.A | + | + | + | + | + | N.A | N.A | + |
Mhyo vaccination of gilts | ||||||||||
 At the supplier | + |  |  |  | + |  |  |  |  | + |
 In the quarantine |  |  | + | + | + | + | + |  |  | + |
 During rearing |  | + |  |  |  |  |  | + |  |  |
Mhyo vaccination of sows | − | − | − | − | − | − | − | − | − | − |
First contact gilts-sows in insemination unit | + | + | + | + | + | + | + | + | + | + |
Group housing after … days of gestation | 28 | 28 | 25 | 25 | 28 | 3 | 28 | 28 | 35 | 28 |
Clinical signs of respiratory disorders | ||||||||||
 Sows/gilts | − | + | − | − | − | + | + | + | + | − |
 Young piglets | − | + | − | − | + | − | − | − | + | − |
Mhyo positive TBS (%, number) | 2.5 2/80 | 43.8 35/80 | 3.8 3/80 | 0.0 0/80 | 33.8 27/80 | 20.0 16/80 | 18.8 15/80 | 40.0 32/80 | 5.0 4/80 | 7.5 6/80 |
Mhyo seropositive animals (%, number) | 66.3 53/80 | 92.5 74/80 | 76.3 61/80 | 73.8 59/80 | 87.5 70/80 | 91.3 73/80 | 85.0 68/80 | 93.8 75/80 | 32.5 26/80 | 95.0 76/80 |