Table 2.

Seroprevalence^a by sow parity and production flow^b of Actinobacillus pleuropneumonia (App), Mycoplasma hyopneumoniae (Mhyo) and swine influenza virus (SIV) in finisher pigs, born within one week from a single farrowing batch and followed from birth to slaughter on an Irish farrow-to-finish commercial farm

Predictor variables	App	Mhyo	SIV
Sow parity
1	97.4	100	81.6
2	91.9	100	81.8
3	92.5	100	83.0
4	90.7	100	80.0
5+	76.6	100	70.2
Production flow
1	86.1	100	86.1
2	91.8	100	71.5
3	93.2	100	71.2

^aSerum samples were analysed using enzyme-linked immunosorbent assay (ELISA) according to the manufacturer’s instructions (IDEXX, Hoofddorp, The Netherlands) for the three respiratory pathogens. Sample-to-positive ratio values were calculated for App and Mhyo while sample-to-negative ratio values were calculated for SIV. Samples with sample-to-positive values ≥0.40 for Mhyo, ≥ 0.50 for APP and samples with sample-to-negative values SIV ≤0.60 were considered as positive as per the criteria given in the manufacturer’s instructions

^bAll pigs were slaughtered at 24 weeks and were retrospectively classified into three production flows according to the time required to move to the next production stage (Flow 1 = normal; Flow 2 = delayed by 1 week; Flow 3 = delayed by more than 1 week). Pigs were selected from each flow in a nested case control study matched by sow parity, birth body weight and number of piglets born alive