Abstract
Hysterectomy-produced, colostrum-deprived (HPCD) pigs and naturally born, enzootic-pneumonia-free (EPF) pigs were compared with respect to their susceptibility to two strains of enzootic pneumonia induced by intranasal inoculation of suspensions of ground pneumonic tissue. All but one of the HPCD pigs developed enzootic pneumonia, whereas the EPF pigs commonly failed to develop the disease; secondly, the pneumonic lesions were more extensive in the HPCD pigs.When the dose of inoculum was increased in EPF pigs, the resulting pneumonic areas were larger.In a small, in-contact experiment the disease was also more readily transmitted to HPCD pigs than to EPF pigs.