Infections with Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae in fattening pigs. Influence of piglet production systems and influence on production parameters.

Two hundred and sixty-four feeder pigs from an age-segregated herd (A-pigs) and 264 feeder pigs from a continuous production system (C-pigs) were transferred into identical but separate rooms in a fattening herd employing all-in all-out production. On arrival, none of the A-pigs and 39% of the C-pigs were seropositive to Mycoplasma hyopneumoniae (M. hyo). At slaughter 30% of the A-pigs and 99% of the C-pigs were seropositive to M. hyo. Pigs with acute swine enzootic pneumonia (SEP) at slaughter and pigs that seroconverted to M. hyo late in the rearing period showed a lower growth rate compared with pigs with chronic SEP or pigs that seroconverted to M. hyo early or not at all. No A-pigs and 12% of the C-pigs were seropositive to Actinobacillus pleuropneumoniae 2 (A. pp 2) at arrival to the fattening herd. At slaughter, 10% of the A-pigs and 13% of the C-pigs were seropositive to A. pp 2. On arrival, the prevalence of pigs seropositive to A. pp 3 was lower among A-pigs than C-pigs. During the fattening period the situation was reversed. The prevalence of pleuritis at slaughter was low (2.7-4.2%) and there were no associations between pleuritis at slaughter and developments of antibodies to A. pp 2 or 3. However, pigs with pleuritis developed antibodies to M. hyo to a greater extent than pigs without pleuritis. Pigs with pleuropneumonia at slaughter and pigs that seroconverted to A. pp 2 or 3 had, during certain periods of the rearing, higher growth rates compared with pigs without pleuropneumonia or pigs that did not seroconvert to A. pp 2 or 3.