The effect of all-in-all-out srowing- finishing on the health of pigs

This study compares all-in-all-out (AlAD) production with continuous-flow(CF) production during the growing-finishing phase. Thirty-three randomly selected pigs were moved into a room designated as the AIAD facility at approximately 17-20 kg (37-44 Ib) body weight. These pigs may have been infected with Mycoplasma hyopneumoniae and Pasteurella multocida but were not exhibiting clinical signs of pneumonia at this age.They remained in that facility until they attained 101-120 kg (222-264 Ib) body weight and were slaughtered. Thirty-three randomly selected pigs were at the same time moved into a room (identical to the AIAD room) that was designated as the CF room. Nine of these 33 pigs were from the same cohort as the AIAD pigs. The other 24 pigs were older, ranging between 3-5 months of age, and were from the same farm but came from the CF finishing unit. These older CF pigs were presumed to be naturally infected with Mycoplasma hyopneumoniae and Pasteurella multocida. Necropsy, examination of lungs at slaughter, bacterial isolations, serologic tests, and fluorescent antibody tests indicated that the younger pigs in the CFroom had been infected with M. hyopneumoniae and P. multocida. Pigs and feed consumed were weighed and recorded monthly. Antimicrobials were not added to rations during this study. Pigs were examined at least once each week for coughing and clinical signs of other maladies. Six replicates of both AIAD and CF groups were completed during a 2-year period. At slaughter, individual pig lungs were examined for lesions of pneumonia. Additionally, 10 lungs from pigs (designated as sentinel pigs) per treatment group were tested by indirect-immunofluorescent assay (lFA) for Mycoplasma hyopneumoniae, and cultured for Pasteurella multocida and other bacterial pathogens, and examined for macroscopic and microscopic lesions.